Related applications
This application is related to the following applications, the entire contents of
which axe incorporated herein by reference:
U S. Patent Application No. 60/703,815, filed July 29, 2005 and entitled "High
Temperature Superconductive Wires and Coils,"
U S. Provisional Application No. 60/703,836, filed July 29, 2005 and entitled
"Thick Superconductor Films With Improved Performance;" and
U.S Provisional Application No. 60/615,289, filed on October 1, 2004 and entitled
'Thick Superconductor Films With Impioved Performance "
Technical Field
This invention relates to the field of high temperature superconductors. In
particular, the invention relates to coated conductor, also called second generation, high
temperature superconductor wires and tapes.
Background
High temperature superconductor (HTS) materials provide a means for carrying
extremely large amounts of current with extremely low loss. HTS materials lose all
resistance to the flow of direct electrical current and nearly all resistance to the flow of
alternating current when cooled below a critical temperature. The development of HTS
wires (the expression "wires" is used here for a variety of conductors, including tape-like
conductors) usmg these materials promises a new generation of high efficiency, compact,
and environmentally friendly electrical equipment, which has the potential to revolutionize
electric power grids, transportation, materials processing, and other industries. However a
commercially viable product has stringent engineering requirements, which has
complicated the implementation of the technology in commercial applications.

In the second generation HTS wire technology, currently under development, the
HTS material is generally a polycrystalline rare-earth/alkaline-earth/copper oxide, e.g.
yttrium-banum-copper oxide (YBCO). The current carrying capability of the HTS
material is strongly related to its crystalline alignment or texture. Grain boundaries
formed by the misalignment of neighboring crystalline HTS grains are known to form an
obstacle to superconducting current flow, but this obstacle decreases with the increasing
degree of alignment or texture. Therefore to make the material into a commercially viable
product, e g an HTS wire, the HTS material must maintain a high degree of crystalline
alignment or texture over relatively long distances. Otherwise, the superconducting
current carrying capacity (critical current density) will be limited.
HTS materials can be fabricated with a high degree of crystallographic alignment
or texture over large areas by growing a thin layer of the material epitaxially on top of a
flexible tape-shaped substrate, fabricated so that it has a high degree of crystallographic
texture at its surface. When the crystalline HTS material is grown epitaxially on this
surface, the crystal alignment of the HTS material grows to match the texture of the
substrate. In other words, the substrate texture provides a template for the epitaxial
growth of the crystalline HTS material. Further, the substrate provides structural integrity
to the HTS layer.
A substrate can be textured to provide a template that yields an epitaxial HTS layer
with excellent superconducting properties such as high critical current density. Materials
such as nickel, copper, silver, iron, silver alloys, nickel alloys, iron alloys, stainless steel
alloys, and copper alloys can be used, among others. The substrate can be textured using a
deformation process, such as one involving rolling and recrystalhzation annealing the
substrate. An example of such a process is the rolling-assisted biaxially textured substrate
(RABiTS) process. In this case large quantities of metal can be processed economically
by deformation processing and annealing and can achieve a high degree of texture. Strips
of metal as wide as, e g., 4 cm have thus far been produced by this method, which can
each then be slit into numerous smaller wires (e g 10 strips of 0 4 cm wires)
One or more buffer layers can be deposited or grown on the substrate surface with
suitable crystallographic template on which to grow the HTS material. Buffer layers also
can provide the additional benefit of preventing diffusion over time of atoms from the
substrate material into the crystalline lattice of the HTS material or of oxygen into the
substrate material. This diffusion, or "poisoning," can disrupt the crystalline alignment

and thereby degrade the electrical properties of the HTS material. Buffer layers also can
provide enhanced adhesion between the substrate and the HTS layer. Moreover, the buffer
layer(s) can have a coefficient of thermal expansion that is well matched to that of the
superconductor material. For implementation of the technology in commercial
applications, where the wire may be subjected to stress, this feature is desirable because it
can help prevent delamination of the HTS layer from the substrate.
Alternatively, a non-textured substrate such as Hastelloy can be used, and textured
buffer layers deposited by means such as the ion-beam-assisted deposition (IBAD) or
inclined substrate deposition (ISD). Additional buffer layers may be optionally deposited
epitaxially on the IB AD or ISD layer to provide the final template for epitaxial deposition
of an HTS layer.
By using a suitable combination of a substrate and one or more buffer layers as a
template, an HTS layer can be grown epitaxially with excellent crystal alignment or
texture, also having good adhesion to the template surface, and with a sufficient barrier to
poisoning by atoms from the substrate. The HTS layer can be deposited byaay of a
variety of methods, including the metal-organic deposition (MOD) process, metal-organic
chemical vapor deposition (MOCVD), pulsed laser deposition (PLD), thermal or e-beam
evaporation, or other appropriate methods. Lasdy, a cap layer can be added to the
multilayer assembly, which helps prevent contamination of the HTS layer from above.
The cap layer can be, e g., silver, and can be, e.g., sputtered onto the HTS layer. An
exemplary multilayer HTS assembly includes a biaxially textured substrate of nickel with
5% tungsten alloy; sequentially deposited epitaxial layeis of Y2O3, YSZ, and CeOz;
epitaxial layer of YBCO; and a cap layer of Ag Exemplary thicknesses of these layers
are: a substrate of about 25-75 microns, buffer layers of about 75 nm each, a YBCO layer
of about 1 micron, and a cap layer of about 1-3 microns. HTS wires as long as 100 m
have been manufactured thus far using techniques such as those described above. In this
assembly the bottom of the substrate can be considered the "back" of the assembly, and
the top of the cap layer can be considered the "front"
During use, it is desirable that the HTS wire is able to tolerate bend strains A
bend induces tensile strain on the convex outer surface of the bend, and compressive strain
on the concave inner surface of the bend, thereby subjecting the HTS layer to tensile or
compressive strains depending on the direction in which the wire is bent While a modest
amount of compressive stress can actually enhance the current carrying capacity of an

HTS layer, in general subjecting the whole assembly to stress (especially repeated stress)
places the wire at risk of mechanical damage. For example, cracks could be formed and
propagate in the HTS layer, degrading its mechanical and electrical properties, or the
different layers could delaminate from each other or from the substrate.
Methods for reducing stress in the HTS layer are described, e.g., in U S. Patent No
6,745,059 and U.S. Patent No. 6,828,507. For example, a copper strip, chosen to have
similar thickness and mechanical features to the substrate, can be bonded onto the upper
surface of the insert. This sandwiches the HTS layer roughly in the middle of the overall
structure, so if the assembly is bent, the HTS layer is neither at the outer nor inner surface
of the bend. Two of these assemblies can also be bonded together at therr respective
copper strips to form a single HTS wire assembly In this case, the two substrates face
outward, and the copper tapes are in the middle of the assembly. In this case the inclusion
of a second assembly provides additional current carrying capacity; however, electrical
contact to the HTS layers requires splicing the wire open, or partially removing one of the
insertS-mrbe.contact section _ _ .. - - - --.
A further issue for coated conductor HTS wires is that of environmental
contamination when the wire is in use Environmental exposure can slowly degrade the
electrical performance of HTS layers. Also, m the presence of cryogenic liquids such as
liquid nitrogen m contact with the wire, the liquid can diffuse into pores within the wire,
and on warming can form "balloons" that can damage the wire Sealing the wire is
desirable to prevent either environmental exposure of the HTS layers or penetration of the
liquid cryogen into the wire. Seals for HTS assemblies are described in, e.g. U.S. Patent
No. 6,444,917.

Summary
Multilayer high temperature superconductor (HTS) wires are described having
improved current sharing, good mechanical properties, superior isolation of the HTS
assembly from the environment, more efficient electrical contact with external electrical
connections or joints, and/or enhanced electrical stabilization. HTS wires having electrical
stabilization that protects the HTS layers m the case of an overcurrent, i.e a current that
exceeds the critical current of the HTS layers, also are described. An overcurrent can
cause the HTS layers to become resistive, and to generate heat. Electrical stabilization
provides an alternate current path if current flow in a local region of an HTS layer is
blocked by a crack or other defect.
A laminated superconductor wire, according to one aspect of the invention,
includes a superconductor wire assembly having a length and a width. The assembly
includes a first superconductor insert having a first high temperature superconductor layer
overlaying a first substrate, and a second superconductor insert having a second high
temperature superconductor layer overlaying a second.substrate .The first_and seco_nd._
superconductor inserts are joined together at their respective substrates. An electrically
conductive structure substantially surrounding the superconductor wire assembly is also
included.
In one aspect of the invention, the electrically conductive structure includes a first
conductive strip and a second conductive strip, and the superconductor wire assembly is
interposed between and is in electrical contact with the first and second conductive strips.
The structure also includes a substantially nonporous electrically conductive filler. The
filler extends between the first and second conductive stnps along the length of the
superconductor wire assembly. In one or more embodiments, the first and second
conductive strips have a width that is greater than the width of the superconductor wire
assembly.
In another aspect of the invention, the electrically conductive structure includes an
electrically conductive layer that partially surrounds and is in electrical contact with the
superconductor wire assembly along at least three sides. The structure also includes a
substantially nonporous electrically conductive filler, wherein the filler substantially
surrounds the superconductor wire assembly and bonds it to the conductive layer. In one
or more embodiments, the substantially nonporous electrically conductive filler

substantially fills voids in the superconductor wire assembly and between the
superconductor wire assembly and the conductive layer.
In another aspect of the invention, the electrically conductive structure includes an
electrically conductive material substantially surrounding and in electrical contact with the
superconductor wire assembly. In one or more embodiments, the electrically conductive
material includes a material selected from the group of electrically conductive polymers,
polymers filled with fine metal powder, and conductive glue.
In one or more embodiments, the electrically conductive material includes a
conductive foil wrapped around the superconductor wire assembly. In one or more
embodiments, at least one layer of a substantially nonporous material substantially
surrounds the conductive foil.
In one or more embodiments, a bonding material bonds the first substrate and
second substrate together. The bonding material may be a material selected from the
group of electrically conductive materials and electrically nonconductive materials.
The.bonding material may include the same matcriaLas the substantially nonporous
electrically conductive filler. The bonding material may include at least one layer of a
conductive material and at least one layer of a non-conductive material. In one or more
embodiments, the first substrate and second substrate have surfaces that are treated to
provide electrical contact between the substrates.
In one or more embodiments, the first and second substrates have a corresponding
firsr and second wertmg layer deposited on a surface of the substrate that opposes the
surface that the HTS layer overlays.
In one or more embodiments, a layer of conductive material substantially
surrounds the superconductor wire assembly.
In another aspect of the invention, a laminated superconductor wire includes a
superconductor wire insert, having a length and a widm The insert includes a high
temperature superconductor layer overlaying a surface of a substrate, and a wetting layer
deposited on a surface of the substrate opposing the high temperature superconductor
layer. The wire also includes an electrically conductive structure, which substantially
surrounds the superconductor wire insert. The electrically conductive structure includes a
first conductive strip and a second conductive strip, wherein the superconductor wire
insert is interposed between and is in electrical contact with the first and second
conductive strips. The electrically conductive structure also includes a substantially

nonporous electrically conductive filler, which extends between the first and second
conductive stops along the length of the superconductor wire insert.
In one or more embodiments, the first and second conductive stops have a width
that is greater than the width of the superconductor wire assembly.
In one or more embodiments, a a layer of conductive material substantially
surrounds the superconductor wire insert.
According to one aspect of the invention, a method of making a laminated
superconductor wire includes providing a superconductor wire assembly having a length
and a width. The assembly includes a first superconductor insert, having a first high
temperature superconductor layer overlaying a first substrate, and a second superconductor
insert having a second high temperature superconductor layer overlaying a second
substrate. The first and second superconductor inserts are joined together at their
respective substrates. The method includes laminating the first and second high
temperature superconductor layers to conesponding first and second conductive strips
- with a substantially nonporous electrically conductive filler.-The-method includes . . ..
depositing additional filler between the first and second conductive stops along the length
of the superconductor wire assembly, such that the first and second conductive strips and
the filler together substantially surround the superconductor wire assembly.
In one or more embodiments, the method includes providing a bonding material
between the first and second substrate. In one or more embodiments, the method includes
providing first and second wetting layers on a surface of the corresponding" first and
second substrates opposite the high temperature superconductor layer.
In one or more embodiments of the invention, the first and/or second
superconductor layers may be made from a lare earth-alkaline earth-copper oxide. Also, a
buffer layer may be interposed between the first and/or second superconductor layers and
the one or more corresponding substrates. Also, an electrically conductive cap layer may
be interposed between, and in electrical contact with, the electrically conductive structure
and a corresponding superconductor layer.
I In another aspect of the invention, a superconductor wire assembly includes- a first
superconductor insert, which includes a first substrate, a first buffer layer overlaying the
first substrate, a first high temperature superconductor layer overlaying the first buffer
layer, and

a cap layer overlaying the first high temperature superconductor layer, and a second
superconductor insert, which includes a second substrate, a second buffer layer overlaying
the second substrate, a second high temperature superconductor layer overlaying the
second buffer layer, and a cap layer overlaying the first high temperature superconductor
layer. The first and second superconductor inserts are joined together at their respective
substrates.
The laminated superconductor wires, according to one or more embodiments of the
invention, have a high current carrying capacity, and at the same time may have improved
current sharing, superior isolation of the HTS assembly from the environment, and ease of
use over previously known wire architectures.
The expression "HTS insert" is intended to indicate a multilayer structure
including a substrate, one or more buffer layers, an HTS layer, and a cap layer Generally
in this HTS insert, the HTS layer is electrically isolated from the metallic substrate by the
buffer layer(s). However, if electrically conductive buffer layers are used, the HTS layer
-can be electrically connected to the metal substrate. Altematively,.an electrically ....
conductive cap layer can be in contact with both the HTS layer and the substrate, and
provide electrical contact between the two.
The expression "HTS assembly" is intended to indicate a structure that mcludes at
least one HTS insert, but which may possibly include one or more HTS inserts and/or
other, added layers. The expression "HTS wire" or "HTS tape" is intended to indicate an
HTS insert or assembly that includes an outer structure or coating that generally provides
structural, thermal, and/or electrical stabilization to the HTS insert or assembly.
The expression "sealed" is intended to mean substantially surrounded and
substantially physically isolated from the environment. The expression "sealed" may
include, but is not required to include, substantial impermeability to penetration from gas
or liquid under normal circumstances.
r- » ACCOMPANYING
Brief Description of thefDrawings
The invention is described with reference to the following figures, which are
presented for the purpose of illustration only and which are not intended to be limiting of
the invention.

FIG. lis a cross-sectional illustration of an assembly having two HTS inserts
joined at their substrates.
FIG. 2A shows a wire having HTS inserts that are bonded together and are
laminated and sealed between two conductive stabilizer strips.
FIG. 2B shows a method of making a wire having HTS inserts that are bonded
together and are laminated and sealed between two conductive stabilizer strips.
FIG 3A shows a wire having two bonded HTS inserts that are sealed inside of a
three-sided conductive trough
FIG. 3B shows a wire having an alternate arrangement of two bonded HTS inserts
that are sealed inside of a three-sided conductive trough.
FIG. 4A shows a wire having two bonded HTS inserts that are sealed inside of a
four-sided conductive structure.
FIG. 4B shows a wire having an alternate arrangement of two bonded HTS inserts
that are sealed inside of a four-sided conductive structure
- - -HG.-5A shows across sectional view of a wire haying two bonded HTS Inserts
that are wrapped with conductive foil and then coated with solder
FIG. 5B shows a lengthwise view of a wire having two bonded HTS inserts that
are wrapped with conductive foil and then coated with solder.
FIG. 6 shows a wire having two bonded HTS inserts that are electroplated with
metal and then laminated and sealed between two conductive stabilizer strips.
FIG. 7 is a cross-sectionalillustration of another embodiment of the present
invention, showing a wire having two HTS inserts that are bonded at their substrates, and
are sealed inside of an electrically conductive structure
FIG. 8 is a cross-sectional illustration of another embodiment of the present
invention, showing a wire having a single HTS insert and a wetting layer, and sealed
inside of an electrically conductive structure.
FIG. 9 illustrates a flow diagram of an exemplary process used to manufacture an
HTS insert.
Detailed Description
High temperature superconducting wires with an electrically conductive outer
structure are described The conductive outer structure has the featuies, among others, of

substantially sealing the wire and of providing electrical contact from the outside of the
wire to the HTS insert. The conductive outer structure further may have the feature of
providing electrical contact between the two HTS inserts.
A multilayer HTS assembly according to one or more embodiments of the
invention is shown in cross-section in FIG. 1. It should be noted that in diis and all
subsequent figures, the dimensions are not to scale Assembly 100 is made up of two HTS
inserts 110 and 120. Each of these inserts is fabricated using techniques known in the art
and that are described in greater detail below. Insert 110 includes a metal substrate 160.
At least a surface of substrate 160 is biaxially textured to provide a crystal template for
buffer layer 150 and HTS layer 140 One or more buffer layer(s) 150 is above substrate
160 and may comprise one or more layers. In one or more embodiments, the buffer layer
is made up of an electrically insulating material, though electrically conductive materials
can be used. The buffer layer is made up of, e.g , an inert metal, an oxide, zirconate,
titanate, niobate, nitride, tantalate, aluminate, cuprate, manganate, or ruthenate of a metal
- - or- rare earth-element (e.g-. -AI2O3, Ce02, Y-iCs, MgO, Gd2C3, strontium titanate, -
gadolinium zirconate, yttria-stabilized zirconia, A1N, S13N4, LaMnQ*, LdvLtiOi, or La2.
xCexZ^O? Any material, or combination of materials, that provides a suitable texture on
which to grow an HTS crystal can be used. HTS layer 140 is above buffer layer 150 may
be any HTS material. In one or more embodiments, the HTS layer, includes a rare earth-
alkaline earth-copper oxide, such as YBCO. Cap layer 130 is located above HTS layer
140 and provides protection of the HTS layer from chemical and mechanical degradation "
The cap layer may be sputtered Ag or other inert metal. Insert 120 may have the identical
or similar structure, including substrate 160', one or more buffer layer(s) 150', HTS layer
140', and cap layer 130'. Further details may be found in commonly-owned U.S. Patent
Application No. (TBA), entitled "High Temperature Superconducting Wires and Coils,"
filed on an even date herewith, which is hereby incorporated in its entirety by reference
In order to facilitate bonding between HTS inserts 110 and 120, several different
approaches are contemplated. These approaches can be readily implemented in the
fabrication of laminated superconductor wires, and may be advantageous in manufacturing
long lengths of HTS wire. In one approach, respective wetting layers 170 and 170' can
optionally be coated onto respective substrates 160 and 160'. These wetting layers
facilitate the bonding of each insert to adhesive layer 180, and therefore facilitate the
bonding of each insert to the other. In one or more embodiments, adhesive layer 180 is

made of solder. An exemplary solder is Pb-Sn-Ag. During processing, the back surfaces
of the metallic substrates (i.e. the surfaces that do not face the buffer layer) may grow a
native oxide layer, which is an electrical insulator. This oxide layer typically does not wet
solder, i.e. does not bond to solder. It has been surprisingly discovered that the addition of
Ag wetting layers 170 and 170' to substrates 160 and 160', respectively, makes the back
surface wettable, i e. bondable, to solder adhesive layer 180. Thus, bonding can be
accomplished by soldering wetting layers that are bonded to the native oxide surfaces of
the substrates.
Deposition of Ag by DC sputtering is a standard operation. Translating coated
conductor tape thought the plasma in a continuous mode without degradation of the
superconductor properties requires cooling of the tape as it passes through the plasma.
The tape is pulled across a cooling block that is positioned opposite the target to minimize
the maximum temperature of the tape during deposition to below -200 C Proximity to
the target may be required for adhesion of the Ag layer on the oxide surface. Energy
—imparted from-the plasma likely cleans the deposition surface in situ and-deposits-the Ag- -
ions with enough impact energy to make good physical contact.
In another approach, appropriate for applications where particularly good electrical
contact between the substrates is desired, the electrically insulating native oxide layers on
substrates 160 and 160' may be first removed. This removal can be done, e.g, by etching,
electro-polishing, sputtering, or shot blasting. Then metallic wetting layers 170 and 170',
e.g., Ag, Cu, Ni, Ti, or TiN, are coated onto the respective back surfaces of substrates 160
and 160' to prevent the regrowth of the native oxide on the substrate surfaces.
Additionally these wetting layers 170, 170' promote adhesion of the bonding layer to the
substrate surface. Then solder adhesive layer 180 bonds the two assemblies together.
Rigorous removal of the native oxide layer is not required, however, in order to achieve
electrical contact between inserts. As is described in greater detail below, the electrical
conductive material that optionally surrounds the multilayer HTS assembly can provide
additional current sharing.
While the embodiment of FIG 1 shows the use of solder and Ag wetting layers to
bond the two substrates together, other adhesive schemes and materials can be used
depending on the desired performance characteristics of the wire. In another approach,
appropriate for applications where electrical isolation of the substrates from each other is
desirable, adhesive layer 180 is for example a resin, epoxy, or other non-conductive

material, and wetting layers 170 and 170' are selected to facilitate bonding between
substrates 160,160', and the non-conducting adhesive layer. In this case it may be that
some of the layers are conductive, and other layers are non-conductive. In applications
where the desired adhesive wets the back substrate surfaces, wetting layers 170 and 170'
can be eliminated entirely. In this case, adhesive layer 180 directly contacts substrates 160
and 160'. In another approach, appropriate for applications where neither electrical
communication nor adhesion between substrates 160 and 160' is needed, for example, in
applications where the substantially sealing electrically conductive material provides
sufficient structural integrity to the wire, wetting layers 170 and 170' as well as adhesive
layer 180 can be eliminated, in which case, the back surfaces of substrates 160 and 160'
are brought directly into contact with each other
In the embodiment illustrated in FIG. 1, adhesive 180 bonds insert 110 to insert
120 at their respective substrates, creating HTS assembly 100. Cap layers 130 and 130'
face outward in assembly 100, and substrates 160 and 160' are central to assembly 100.
This configuratiou provides,"for example, efficient elet-tocal" contact with air external —
current source, and efficient joining of lengths of superconductor wire. The outer surfaces
of the assembly are electrically conductive cap layers 130 and 130'. These layers provide
convenient electrically conductive paths to respective HTS layers 140 and 140'. In order
to introduce current into the HTS layers, a connection between the current source and the
assembly can be made anywhere on the outer surface of the assembly.
FIG. 2A illustrates an embodiment of the present invention, having a wire 200 that
includes two bonded HTS inserts 210, 220, which may be the same as previously
described, and a conductive outer structure. The conductive outer structure substantially
surrounds and seals the wire from the environment, and provides electrical contact
between the two HTS inserts as well as to an external electrical contact. The conductive
outer structure further provides mechanical, thermal, and electrical stabilization to wire
200. The conductive outer structure includes upper and lower conductive s.tabilizer strips
250, 270 and electrically conductive non-porous filler material 290, e.g. solder or another
low-melting temperature alloy or amalgam, a conductive polymer, or a pure metal such as
In. Filler 290 substantially surrounds HTS inserts 210, 220 and also may serve as bonding
layer 180, illustrated in the HTS assembly 100 of FIG 1 As discussed previously,
substrates 260, 260' may be coated with respective wetting layers 230, 230' to enhance
their bonding to filler 290 (and to each other). Filler 290 also bonds inserts 210, 220 to

conductive stabilizer strips 250, 270 at the outer surfaces of the HTS inserts. Filler 290
bridges strips 250, 270 in thick layers on the sides of the wire to thereby complete the
isolation of the HTS assembly from the surrounding environment and to substantially
completely surround the'HTS assembly in a conductive structure.
Occasionally there can be a defect within an HTS layer, which causes a
corresponding increase in the resistance of (and heating in) the layer during use of the
wire. In this case it can be useful to divert, or shunt, some or all of the current into another
HTS layer This results in a more uniform conductor, with a conductivity that does not
vary greatly along the length of the wire. This is of particular use when the operating
current is well below the critical current, a common practice m the operation of
superconducting devices. A two HTS layer structure using a single substrate, having two
HTS layers that are coated on opposing sides of the substrate, has been contemplated as a
method of implementing multiple HTS layers in a single wire in order to provide
redundant superconducting pathways. However, this sort of structure suffers from having
—a very-complicated-manufactunng process with limited flexibility as to the electrical
relationship between and composition of the two HTS layers. ID contrast, the
embodiments of the present invention, having two HTS inserts laminated together- at their
substrates, offer the benefits of ease of manuf actunng, as well as ease of tailoring the
structures to a particular desired application.
In wire 200, filler 290 provides electrical communication between the HTS inserts
210, 220. In essence filler 290 behaves as a conductive conduit, or bridge Though filler
290 is conductive, as current flows through wire 200, the current will generally follow the
path of least resistance, which is through one or both HTS inserts 210, 220. However if
one of HTS inserts 210, 220 has a defect that increases its resistance in a certain region,
the current can flow through filler 290 into the other HTS insert Filler 290 has a higher
resistance than HTS inserts 210, 220, so the current transfers between the inserts over
some calculable length (e.g. a few centimeters) of the wire The net result of the transfer
is that the current can continue traveling along a low resistance path, i.e through the other
HTS insert. If there is a defect at a different region in this insert, then the current can
transfer back to the other insert, which is unlikely to also have a defect in the same place
The presence of redundant electrical pathways for the current improves the electrical
stability of the wire. The current capacity of wire 200 is much less sensitive to local

defects in either of HTS inserts 210, 220 than it would be with a single insert, where the
current would be forced through a high resistance section of the wire.
Providing electrical communication between HTS inserts 210, 220, with filler 290,
also increases the current-carrying capacity of wire 200 over that of a single insert, or two
isolated inserts. The critical current, Ic, and the engineering (total) critical current density,
Je, are both increased. Filler 290 provides a means to introduce electrical current into one
or both of HTS inserts 210, 220. By simply contacting a current source to filler 290,
current flows via the filler into the HTS inserts. Because filler 290 is in contact with
conductive stabilizer strips 250, 270, contacting a current source to one or both of
strips250, 270 also introduces current to one or both of HTS inserts 210, 220.
Material 290 is selected such that it is nonporous;"in one or more embodiments, it
is has sufficient strength and is coated with sufficient thickness to substantially surround
and seal wire 200. This renders HTS inserts 210 and 220 substantially impervious to
contamination by environmental factors, which can degrade the electrical performance of
. theinserts.. Filler 290-may also-substantially-prevent infiltration of the-assemblies-by -
surrounding cryogenic fluid, which can form balloons that can potentially mechanically
damage the HTS inserts The thick coating of filler 290 on the sides of wire 200 also adds
mechanical strength to the wire and may help to prevent delammation of wire 200 due to
bending or other sources of potential damage. Material 290 adds thermal stability to the
wire by providing additional heat capacity
Stabilizer strips 250 and 270 further enhance the mechanical, electrical, and
thermal stability of wire 200. Strips 250, 270 can be the same or different, depending
upon the desired characteristics of the resulting wire. The thickness of the stops can be
varied throughout a wide range of about 0.01-2 mm, depending upon the desired
application. For superconducting cables, the thickness is typically between 0.05-0.075
mm. For a fault current limiter application, the stabilizer thickness can be as high as or
higher than 1 mm. The material used for strips 250 and 270 is selected to provide an
appropriate electrical, thermal, and mechanical stability to wire 200 for the desired
application. Strips 250 and 270 are generally a flexible conductive material, e g. metal,
e.g. aluminum, copper, silver, nickel, iron, stainless steel, duminum alloy, copper alloy,
silver alloy, nickel alloy, nickel tungsten alloy, or iron alloy. For most applications, a high
conductivity metal such as copper is preferred. For a fault current limiter application, a
mechanically strong, high resistivity alloy such as stainless steel is preferred.

la some embodiments, stabilizer strips 250 and 270 have a width that is greater
than the width of HTS inserts 210 and 220. This excess width, or overhang, allows layers
or fillets of filler 290 to form along the sides of the wire by capillary action. In a preferred
embodiment, the fillets have a concave profile relative to the edge of the wire. Because
such fillets form by capillary action, the excess width ot strips 250, 270 over the width of
HTS assemblies 210, 220 determines the thickness of the fillet Generally, the width of
strips 250,270 fall within the range of 0 01-2 mm greater than the width of HTS
assemblies 210, 200. For example, stabilizer strips with a width of about 4.3 mm can be
used with 4.0 or 4.1 mm wide superconducting inserts Fillets can enhance the mechanical
strength and durability of wire 200 A wider fillet enhances strength, but reduces the
engineering critical current density. An optimally designed wire will have sufficient filler
width to meet the mechanical specifications, but not much more. A typical individual
fillet width ranges from 0.025-0.2 mm, but can be higher or lower (e.g 0.005-1 mm) to
meet specific strength or engineering critical current needs.
Among"other reasons, thick fillets of fiilei 290 enhance the mechanical strength of - -
wire 200 because substrates 260, 260' may not bond well to solder due to their oxidation
during insert processing, as described previously. While wetting layers (e g 230, 230')
can be deposited on the substrate surfaces to improve their bonding to solder, depositing
such a coating on the sides of the wire, e g , on the exposed edges of the multilayer HTS
inserts 210, 220, may not be practical because of increased production cost However,
thick fillets of filler 290 can be deposited on the sides of wire 200, such that the filler
adheres sufficiently to the other (non-substrate) layers of the multilayer assembly, and has
sufficient strength, that it will not delammate from the substrate sides. Some materials
used as filler 290, e.g. Sn-Pb-Ag solders, strengthen considerably (up to three-fold) when
cooled from room temperature to 77 K, and their contribution to the total strength can be
significant.
By adjusting the overhang of stabilizer strips 250, 270 over HTS inserts 210, 220,
the fillet can be made appropriately thick. As a typical example, the following wire can be
illustrative: a 40 mm wide conductor is, after completion of all buffer and superconductor
deposition/reaction steps, coated on both sides with a 0.003 mm thick Ag layer using
sputter deposition. The 40 mm wide conductor is slit in a reel to reel fashion into eight 4.1
mm wide inserts. Each insert is laminated m a reel-to-reel lamination process to a 0 05 x
4.3 mm copper 155 stabilizer strip on both sides, using a Sn-Pb solder to which some Ag

can be added. The resulting wire varies in width between 4 3-4.4 mm. The solder fillet
width is about 0.15-0.2 mm on average.
Wire 200 may be manufactured as illustrated in FIG. 2B. HTS wire inserts are
fabricated as wide (e.g. about 4 to 10 cm wide) multilayer strips and then slit lengthwise
into several narrow (e.g. about 10 strips of about 0 4 cm wide, from a 4 cm wide strip)
strips, which form HTS inserts 210, 220 Conductive stabilizer strips 250, 270 may be
wider than the width of the narrow HTS strip, so that the stabilizer strips overhang the
HTS strip on both sides. After slitting, the wire is formed by joining narrow HTS insert
strips 210, 220 with stabilizer strips 250, 270 in a bath of filler 290. Multilayer HTS
inserts 210, 220, for example, may be fed into the filler bath from reels. Stabilizer strips
250, 270 may be fed off reels placed above and below the feed-m reels of HTS inserts 210,
220 so that the lengths of material form a stacked configuration. The filler simultaneously
surrounds HTS inserts 210, 220 and also laminates them to the conductive stabilizer strips
250; 270. the 295-merges and-consolidates-inserts 210, 22a and stabilizer stops- 250, 270 - -
into one superconducting wire 200.By laminating the stabilizer strips to the wire after
fabricating and slitting the HTS inserts, the stabilizer strips can easily be made wider than
the inserts. The overhanging feature promotes the capillary wicking of the solder between
the upper and lower stabilizer strips 250, 270 to provide thick, mechanically robust fillets
of filler 290 on the sides of the wire.
FIG. 3A shows another embodiment ol the present invention, having wire 300 that
includes an HTS assembly including two bonded HTS inserts 310, 320, which may be the
same as previously described, and a conductive outer structure. The conductive outer
structure includes a first component 350 covering 3 sides of the HTS assembly, e g , a
three-walled trough, which can be assembled, a single part, or in a plurality of pieces, and
electrically conductive non-porous filler 390. Filler 390, e.g., solder, surrounds inserts
310, 320 and bonds them together at their substrates as previously described Filler 390
provides an electrical pathway between three-sided component 350 and HTS inserts 310,
320, and also between the inserts. Filler 390 seals inserts 310, 320 into three-sided
component3 50.
Three-sided component 350 is made fiom a flexible conductive material, e g
metal, e.g. aluminum, copper, silver, nickel, iron, stainless steel, aluminum alloy, copper
alloy, silver alloy, nickel alloy, nickel tungsten alloy, or iron alloy. As described above

for stabilizer strips 250 and 270 in FIG 2A, the material for three-sided component 350 is
selected to provide electrical, thermal, and mechanical stability to the wire for the desired
application. The walls of the three-sided component can have a thickness between, for
example, 0.0001-0.5 mm, and can be thicker depending on the desired application (e.g.
0.0001-1 mm). Three-sided component 350 has a width that is wider than inserts 310 and
320, and a depth that is deeper than the thickness of the HTS assembly. This allows for a
sufficiently thick layer of filler 390 to substantially surround the assembly on all sides and
to substantially seal wire 300. Wire 300 is manufactured by first providing HTS inserts
310, 320, which can be slit from wide strips as described previously. Then in a bath of
filler 390, e g. solder, inserts 310, 320 are simultaneously bonded together, surrounded by
filler 390, inserted into three-sided component 350, and sealed into the three-sided
component.
FIG. 3B shows a wire having an alternate arrangement of two bonded HTS inserts
310', 320', which may be the same as previously described, that are sealed inside of three-
sided component 350'-. Electrically conductive-non-porous fillsi-390',-e-g.-,-solder,
substantially surrounds inserts 310' and 320' and bonds them together at their substrates.
Filler 390' provides an electrical pamway to and between HTS inserts 310', 320'. Filler
390' seals inserts 310', 320' into three-sided component350', which may be the same as
described previously. In this wire three-sided component 350' has a width that is wider
than the thickness of the assembly, and a depth that is deeper than the width of the
assembly. This allows for a sufficiently thick layer of filler 390' to substantially surround
the assembly on all sides and to substantially seal wire 300'. Wire 300' may be
manufactured as described for FIG. 3A.
FIG. 4A shows a wire 400 having HTS inserts 410,420, which may be the same as
previously described, that are sealed mside of a four-walled structure 450, which may
provide additional mechanical stability over the three-walled trough of FIGS. 3A and 3B.
Electrically conductive non-porous filler 490, e.g., solder, surrounds inserts 410,420 and
bonds them together at their substrates as previously described. Filler 490 provides an
electrical pathway to and between HTS inserts 410,420. Filler 490 seals inserts 410, 420
into four-walled structure 450. The internal dimensions of structure 450 are larger than
the appropriate dimensions of bonded HTS inserts 410 and 420. This allows for a
sufficiently thick layer of solder to substantially surround the inserts on all sides and
substantially seal wire 400. Wire 400 can manufactured by first providing the HTS

inserts, which can be slit from wide strips as described previously. One of the walls of
structure 450 is left open in order to leave an adequate space to receive HTS inserts 410
and 420. In a solder bath, the inserts are then simultaneously inserted into structure 450,
bonded together, and surrounded by solder. The open wall of structure 450 is then
mechanically folded over, enclosing the inserts and solder. Solder fills the gap left from
the fold, as can be seen in the figure.
FIG. 4B shows a wire 400' having an alternate arrangement of two bonded HTS
inserts 410', 420', which may be the same as previously described, that are sealed mside
of four-walled structure 450'. Electrically conductive non-porous filler 490', e.g., solder,
surrounds inserts 410', 420' and bonds them together at their substrates as previously
described. Filler 490' provides an electrical pathway to and between HTS inserts 410',
420'. Filler 490' seals inserts 410', 420' into four-walled structure 450'. The internal
dimensions of structure 450' are larger than the appropriate dimensions of bonded HTS
inserts 410', 420'. This allows for a sufficiently thick layer of solder to surround the
" inserts on~all sides "and seal the-structure - Wire 400' -may be manufactured as dessribed-for-
FIG. 4A.
In another embodiment, shown in different perspectives in FIG. 5A and 5B, a thin
conductive foil is wrapped around an HTS assembly. In cross-sectional view FIG. 5A,
adhesive 580 bonds together HTS inserts 510, 520, which may be the same as previously
described. Conductive foil 590 is tightly and contiguously wrapped around the bonded
inserts. This places foil 590 in good electrical contact with inserts 510, 520, and provides
a route for electrical communication between the inserts. As can be seen in FIG. 5B, each
consecutive wrap of foil 590' around inserts 510', 520' overlaps with the previous wrap,
providing a seal around the wire The thickness of the foil can be varied m a wide range,
depending on the application, for example between 0.0001-0.5 mm. Substantially
nonporous sealer 570 is coated on top of foil 590. Sealer 570 can be a electrically
conductive material, in which case sealer 570 and foil 590 together provide an electrical
pathway from the outside of the wire to HTS inserts 510, 520. In another embodiment,
sealer 570 can be a substantially nonporous non-conductive material, m which case the
exterior of wire 500 is electrically insulated In this case to make a conductive connection
from the outside of wire 500 to HTS inserts 510, 520, sealer 570 must be stripped away.
This allows access to conductive foil 590, which is in electrical contact with HTS inserts
510, 520. Wire 500 can be manufactured by providing and bonding HTS inserts 510, 520

as described previously, and then mechanically wrapping conductive foil 590 around the
resulting assembly. Then wire 500 can be run through a bath of sealer 570, e g. solder,
which substantially surrounds and seals wire 500.
In another embodiment, shown in FIG. 6, wire 600 includes two HTS inserts 610,
620, which are bonded with adhesive 680 and may be the same as described previously,
layer 690, and a two-tape structure like that shown in FIG. 2A Layer 690 substantially
surrounds and provides electrical contact between 610, 620, 680. Layer 690 is, for
example, a metallic coating that is deposited onto assembly 610, 620, 680 Cu, Ag, Ti,
TiN, and Sn are examples of metals that can be deposited onto the assembly Alternately,
layer 690 is e.g, a coating of a conductive polymer, a polymer containing metallic powder,
or conductive glue, to result in a conductive medium Whatever the chosen coating,
conductive stabilizer strips 650, 660 are laminated to the assembly with filler 670 as
described for the wire shown in FIG 2. Filler 670 may be the same as described for FIG
2. Stabilizer stops 650, 660, along with filler 670, provide structural, thermal, and
- electrical integrity to-wire 600 beyond that provided by-layer 69D. Because.wire 600 _
contains many features that enhance its strength and durability, it is useful for applications
with harsh environmental conditions or excessive mechanical stress The coated assembly
610, 620, 680, 690 can also be inserted in any of the above-described embodiments, for
applications requiring additional stability.
In one or more embodiments of the present invention, as illustrated in FIG. 7, a
wire includes two HTS inserts 710, 720, which are bonded with adhesive 780 and may be
the same as described previously, and an electrically conductive layer 790 Layer 790
may substantially surround and seal the HTS assembly 710, 720, 780. Layer 790 provides
electrical communication between HTS inserts 710,720. Layer 790 can be a deposited
metal coating The metal can be deposited by an electroplating process, by a metal
powder sintering process, or by an electroless platmg process. Electroplating, powder
sintering, and electroless platmg methods are well known. Cu, Ag, Ti, TiN, and Sn are
examples of metals that can be deposited onto assembly 710, 720,780. In other
embodiments, layer 790 is a conductive polymer, or a polymer containing metallic
powder. Polymer coatings can be applied through a reel-to-reel dip coating and curing
process, with dies or wipes in-line to control the polymer layer thickness. Still other kinds
of conductive materials can be used for layer 790. These materials have the property of
providing good electrical contact between HTS inserts 710, 720 and/or between HTS

inserts 710, 720 and an external conductive contact. These materials also can be
substantially nonporous, and can be deposited with a thickness sufficient to substantially
surround and seal the resulting wire 700.
While the embodiments described above are wires that include HTS inserts that are
bonded together by their substrates, and inserted inside of different kinds of outer
structures, other HTS assemblies can be contemplated for use in any of the described
wires. For example, in one or more embodiments the coated wire 700 of FIG 7 can itself
be inserted mto one or more of the described outer conductive structures.
The novel wetting layers described herein that are used in conjunction with
multiple HTS inserts can also be used to prepare single HTS inserts having an electrically
conductive outer structure. In one or more embodiments, a single HTS assembly can be
inserted into one or more of the above described outer structures Referring to FIG. 8,
wire 8,00 includes an HTS insert 810 that may be the same as described previously. Wire
800 also includes an outer structure 890, where outer structure 890 represents the outer
• conductive structure of any of the embodiments illustrated in FIGS. 2-7. HTS insert 810
includes substrate 860, buffer layer 850, HTS layer 840, and cap layer 830, which may
have the same components and characteristics as insert 110 in the configuration shown in
FIG. 1. Insert 810 also has a wetting layer 870 that is deposited on substrate 860. In this
case wetting layer 870 is selected such that it allows for good adhesion between substrate
860 and outer structure 890. Outer structure 890 is in electrical contact with HTS layer
840. Thus by simply contacting a current source to outer structure 890, current will flow
into the HTS layer. Outer structure 890 substantially surrounds and seals HTS insert 810.
While the described wires contain HTS inserts and assemblies having a substrate,
one or more buffer layer (s), rare earth oxide superconductor, and cap layer, the wires are
not constrained to using these specific kinds of superconductor inserts or assemblies Any
kind of HTS assembly can be used, provided that it contains an HTS layer. For example, a
mesh-type stabilizer having low conductivity in the weft (perpendicular to the wire axis)
and high conductivity in the warp (along the wire axis) can be used in place of conductive
stabilizer strips. This type of stabilizer has the advantage of reducing eddy current losses
in alternating current applications Further details of appropriate mesh-type stabilizers
maybe found m commonly-owned U.S Patent Application, U.S.S.N. 60/667,001, entitled
"Mesh-Type Stabilizer for Filamentary Coated Superconductors," which is hereby
incorporated m its entirety by reference.

Fig. 9 illustrates a flow diagram of an exemplary process used to manufacture an
HTS wire according to various embodiments of the present invention At a first station -
910, a wire substrate is treated to obtain biaxial texture. Preferably, the substrate surface
has a relatively well defined crystallographic orientation. For example, the surface can be
a biaxially textured surface (e.g., a (113)[211] surface) or a cube textured surface (e.g., a
(100)[011] surface or a (100)[001] surface). Preferably, the peaks in an X-ray diffraction
pole figure of the surface have a FWHM of less than about 20° (e.g., less than about 15°,
less than about 10°, or from about 5° to about 10°)
The surface can be prepared, for example, by rolling and annealing. Surfaces can
also be prepared using vacuum processes, such as ion beam assisted deposition, inclined
substrate deposition and other vacuum techmques known in the art to form a biaxially
textured surface on, for example, a randomly oriented polycrystalline or amorphous
surface. In certain embodiments (e.g., when ion beam assisted deposition is used), the
surface of the substrate need not be textured (e g., the surface can be randomly oriented
polycrystalline, ortiae surface can be amorphous). - - -.-_._.
The substrate can be formed of any material capable of supporting a buffer layer
stack and/or a layer of superconductor material, and capable of providing the mechanical
properties required for the final wire. Examples of substrate materials that can be used as
the substrate include for example, metals and/or alloys, such as nickel, silver, copper, mc,
aluminum, iron, chromium, vanadium, palladium, molybdenum and/or their alloys. In
some embodiments, the substrate, can be formed of a superalloy In certain embodiments,
the substrate can be in the form of an object having a relatively large surface area (e g, a
wire or a wafer). In these embodiments, the substrate is preferably formed of a relatively
flexible material.
In some of these embodiments, the substrate is a binary alloy that contains two of
the following metals: copper, nickel, chromium, vanadium, aluminum, silver, iron,
palladium, molybdenum, tungsten, gold and zinc. For example, a binary alloy can be
formed of nickel and chromium (e.g , nickel and at most 20 atomic percent chromium,
nickel and from about five to about 18 atomic percent chromium, or nickel and from about
10 to about 15 atomic percent chromium). As another example, a binary alloy can be
formed of nickel and copper (e.g., copper and from about five to about 45 atomic percent
nickel, copper and from about 10 to about 40 atomic percent nickel, or copper and from
about 25 to about 35 atomic percent nickel). As a further example, a binary alloy can

contain nickel and tungsten (e.g., from about one atomic percent tungsten to about 20
atomic percent tungsten, from about two atomic percent tungsten to about 10 atomic
percent tungsten, from about three atomic percent tungsten to about seven atomic percent
tungsten, about five atomic percent tungsten). A binary alloy can further mclude relatively
small amounts of impurities (e.g, less than about 0.1 atomic percent of impurities, less
than about 0.01 atomic percent of impurities, or less than about 0 005 atomic percent of
impurities). Ni-5wt.%W is a preferred material for the substrate.
In certain of these embodiments, the substrate contains more than two metals (e g.,
a ternary alloy or a quartemary alloy) In some of these embodiments, the alloy can
contain one or.more oxide formers (e.g., Mg, Al, Mo, Y, Ta, Ti, Cr, Ga, Ge, Zr, Hf, Y, Si,
Pr, Eu, Gd, Tb, Dy, Ho, Lu, Th, Er, Tm, Be, Ce, Nd, Sm, Yb and/or La, with Al being the
preferred oxide former), as well as two of the following metals- copper, nickel, chromium,
mngsten, vanadium, aluminum, silver, iron, palladium, molybdenum, gold and anc, In
certain of these embodiments, the alloy can contain two of the following metals: copper,
" nickel,-chroEaium, tungsten, vanadium, aluminum, silver, iron,-palladium, molybdenum,-
gold and zinc, and can be substantially devoid of any of the aforementioned oxide formers.
In embodiments in which the alloys contain an oxide former, the alloys can contain
at least about 0.5 atomic percent oxide former (e g , at least about one atomic percent
oxide former, or at least about two atomic percent oxide former) and at most about 25
atomic percent oxide former (e g., at most about 10 atomic percent oxide former, or at
most about four atomic percent oxide former) For example, the alloy can include an
oxide former (e g., at least about 0 5 aluminum), from about 25 atomic percent to about 55
atomic percent nickel (e.g., from about 35 atomic percent to about 55 atomic percent
nickel, or from about 40 atomic percent to about 55 atomic percent nickel) with the
balance being copper As another example, the alloy can include an oxide former (e.g , at
least about 0.5 atomic aluminum), from about five atomic percent to about 20 atomic
percent chromium (e.g., from about 10 atomic percent to about 18 atomic percent
chromium, or from about 10 atomic percent to about 15 atomic percent chromium) with
the balance being nickel. The alloys can include relatively small amounts of additional
metals (e.g., less than about 0.1 atomic percent of additional metals, less than about 0.01
atomic percent of additional metals, or less than about 0.005 atomic percent of additional
metals).

A substrate formed of an alloy can be produced by, for example, combining the
constituents in powder form, melting and cooling or, for example, by diffusing the powder
constituents together m solid state. The alloy can then be formed by deformation texturing
(e.g, annealing and rolling, swaging, extrusion and/or drawing) to form a textured surface
(e.g., biaxially textured or cube textured). Alternatively, the alloy constituents can be
stacked in a jeUy roll configuration, and then deformation textured. In some
embodiments, a material with a relatively low coefficient of thermal expansion (e.g, Nb,
Mo, Ta, V, Cr, Zr, Pd, Sb, NbTi, an intermetallic such as NiAl or Ni3Al, or mixtures
thereof) can be formed into a rod and embedded into the alloy prior to deformation
texturing.
In some embodiments, stable oxide formation at the surface can be mitigated until
a first epitaxial (for example, buffer) layer is formed on the biaxially textured alloy
surface, using an intermediate layer disposed on the surface of the substrate. Intermediate
layers include those epitaxial metal or alloy layers that do not form surface oxides when
' exposed to conditions as established by PO2 and temperatuie required for the initial -----
growth of epitaxial buffer layer films. In addition, the buffer layer acts as a barrier to
prevent substrate element(s) from migrating to the surface of the intermediate layer and
forming oxides during the initial growth of the epitaxial layer Absent such an
intermediate layer, one or more elements in the substrate would be expected to form
thermodynamically stable oxide(s) at the substrate surface which could significantly
impede the deposition of epitaxial layers due to, for example, lack of texture in this oxide
layer.
Exemplary intermediate metal layers include nickel, gold, silver, palladium, and
alloys thereof. Additional metals or alloys may include alloys of nickel and/or copper
Epitaxial films or layers deposited on an intermediate layer can include metal oxides,
chalcogenides, hahdes, and nitrides In some embodiments, the intermediate metal layer
does not oxidize under epitaxial film deposition conditions
Care should be taken that the deposited intermediate layer is not completely
incorporated into or does not completely diffuse into the substrate before nucleation and
growth of the initial buffer layer structure causes the epitaxial layer to be established. This
means that after selecting the metal (or alloy) for proper attributes such as diffusion
constant in the substrate alloy, thermodynamic stability against oxidation under practical
epitaxial buffer layer growth conditions and lattice matching with the epitaxial layer, the

thickness of the deposited metal layer has to be adapted to the epitaxial layer deposition
conditions, in particular to temperature
Deposition of the intermediate metal layer can be done in a vacuum process such
as evaporation or sputtering, or by electro-chemical means such as electroplating (with or
without electrodes). These deposited intermediate metal layeis may or may not be
epitaxial after deposition (depending on substrate temperature durmg deposition), but
epitaxial orientation can subsequently be obtained during a post-deposition heat treatment.
In certain embodiments, sulfur can be formed on the surface of the substrate or
intermediate layer. The sulfur can be formed, for example, by exposing the intermediate
layer to a gas environment containing a source of sulfur (e.g., H2S, a tantalum foil or a
silver foil) and hydrogen (e.g, hydrogen, or a mix of hydrogen and an inert gas, such as a
5% hydrogen/argon gas mixture) for a period of time (e.g., from about 10 seconds to about
one hour, from about one minute to about 30 minutes, from about five minutes to about 15
minutes). This can be performed at elevated temperature (e.g , at a temperature of from
■abour450°CtD abour 1100°C,from aboat 600°G to about 900°C, 850°C). -The pressure of. . ..
the. hydrogen (or hydrogen/inert gas mixture) can be relatively low (e.g, less than about
one ton, less than about lxlO"3 ton, less than about lxlO"6 torr) or relatively high (e.g ,
greater than about 1 torr, greater than about 100 torr, greater than about 760 torr)
Without wishing to be bound by theory, it is believed that exposing the textured
substrate surface to a source of sulfur under these conditions can result rn the formation of
a superstructure (e.g., a c(2x2) superstructure) of sulfur on the textured substrate surface.
It is further believed that the superstructure can be effective in stabilizing (e.g., chemically
and/or physically stabilizing) the surface of the intermediate layer.
While one approach to forming a sulfur superstructure has been described, other
methods of forming such superstructures can also be used. For example, a sulfur
superstructure (e.g., S c(2x2)) can be formed by applying an appropriate organic solution
to the surface of the intermediate layer by heating to an appropriate temperature in an
appropriate gas environment. Moreover, while formation of a sulfur superstructure on the
surface of the intermediate layer has been described, it is believed that other
superstructures may also be effective in stabilizing (e g., chemically and/or physically
stabilizing) the surface. For example, it is believed that an oxygen superstructure, a
nitrogen superstructure, a carbon superstructure, a potassium superstructure, a cesium

superstructure, a lithium superstructure or a selenium superstructure disposed on the
surface may be effective in enhancing the stability of the surface
In a second processing station 920, a buffer layer is formed on the textured
substrate by epitaxial growth on a textured metal surface. Alternatively, a buffer layer can
be formed on a polycrystalline, randomly textured metal surface using ion beam assisted
deposition (IBAD). In this technique, a buffer layer material is evaporated using, for
example, electron beam evaporation, sputtering deposition, or pulsed laser deposition
while an ion beam (e g., an argon ion beam) is directed at a smooth amorphous surface of
a substrate onto which the evaporated buffer layer material is deposited.
For example, the buffer layer can be formed by ion beam assisted deposition by
evaporating a buffer layer material having a rock-salt like structure (e.g., a material having
a rock salt structure, such as an oxide, including MgO, or a nitride) onto a smooth,
amorphous surface (e.g., a surface having a root mean square roughness of less than about
100 Angstroms) of a substrate so that the buffer layer material has a surface with
substantial-alignment (e.g., about 13° or less),-both m-pl^ne and out-of-plane . ... _. . .._
The conditions used during deposition of the buffer layer material can include, for
example, a substrate temperature of from about 0°C to about 750°C (e.g., from about 0°C
to about 400°C, from about loom temperature to about 750°C, from about room
temperature to about 400°C), a deposition rate of from about 1.0 Angstrom per second to
about 4.4 Angstroms per second, an ion energy of from about 200 eV to about 1200 eV,
and/or an ion flux of from about 110 microamperes per square centimeter to about 120
microamperes per square centimeter.
In some embodiments, when using IB AD, the substrate is formed of a material
having a polycrystalline, non-amorphous base structure (e.g., a metal alloy, such as a
nickel alloy) with a smooth amorphous surface formed of a different material (e g., S13N4),
In certain embodiments, a plurality of buffer layers can be deposited by epitaxial
growth on an original IBAD surface Each buffer layer can have substantial alignment
(e.g., about 13° or less), both in-plane and out-of-plane
A buffer material can be prepared using solution phase techniques, including
metalorganic deposition, such as disclosed in, for example, S.S. Shoup et al., J. Am. Cer.
Soc., vol. 81, 3019; D. Beach et al., Mat Res. Soc. Symp. Proc, vol 495, 263 (1988); M.
Paranthaman et al., Superconductor Sci. Tech., vol. 12, 319 (1999); D.J. Lee et al.,
Japanese J. Appl. Phys., vol 38, L178 (1999) and M W. Rupich et al., LE.E.E. Trans, on

Appl. Supercon. vol 9, 1527. In certain embodiments, solution coating processes can be
used for epitaxial deposition of one or a combination of any of the oxide layers on textured
substrates; however, they can be particularly applicable for deposition of the initial (seed)
layer on a textured metal substrate The iole of the seed layer is to provide 1) protection of
the substrate from oxidation during deposition of the next oxide layer when carried out in
an oxidizing atmosphere relative to the substrate (for example, magnetron sputter
deposition of yttna-stabilized zirconia from an oxide target); and 2) an epitaxial template
for growth of subsequent oxide layers. In order to meet these requirements, the seed layer
should grow epitaxially over the entire surface of the metal substrate and be free of any
contaminants that may interfere with the deposition of subsequent epitaxial oxide layers.
The formation of oxide buffer layers can be earned out so as to promote wetting of
an underlying substrate layer. Additionally, in particular embodiments, the formation of
metal oxide layers can be carried out using metal allcoxide precursors (for example, "sol
gel" precursors).
Once .the .textured, substrate including buffer J ayers is prepared, aprecursor solution-
is deposited at deposition station 930 as described above. Optionally, the precursor can be
patterned. Additional equipment may be required to accomplish the patterning operation,
for example, when laser ablation or ion bombardment are used to pattern the
superconducting layer. If dropwise patterned deposition is used, then a single station
equipped with a inkjet printer deposition apparatus can accomplish both deposition and
patterning of the oxide precursor solution.
Typically, solution chemistry is used to prepare barium fluoride and/or other
superconductor precursors; and a solution (e g, a solution containing metal salts, such as
yttrium acetate, copper acetate, barium acetate and/or a fluormated acetate salt of barium)
is disposed on a surface (e.g., on a surface of a substrate, such as a substrate having an
alloy layer with one or more buffer layers disposed thereon) The solution can be disposed
on the surface using standard techniques (e.g, spin coating, dip coating, slot coating) The
solution is dried to remove at least some of the organic compounds present in the solution
(e.g., dried at about room temperature or under mild heat), and the resulting material is
reacted (e.g., decomposed) in a furnace in a gas environment containing oxygen and water
to form barium fluoride and/or other appropriate materials (e g., CuO and/or Y203). In
some embodiments, the reactors noted above can be used m any or all of these steps.

Metal salt solutions are prepared using metal sources in the appropriate
proportions desired m the resulting superconductor layer. Thus, for example, an additional
amount of copper salt, m excess of the stoichiometric proportions used in YBCO, is
included in a precursor solution used to prepare a high Ic(ab) superconductor layer having
excess copper. Similarly, the precursor solution may contain additive components,
including soluble and insoluble metal compounds, that are used to modify the final
superconductor composition. Such additives can include, for example, soluble compounds
of metal compounds such as yttrium, neodymium, samarium, europium, gadolinium,
terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, alkaline earth
metals, such as calcium, manganese, iron, cobalt, nickel, zirconium, cerium, silver,
aluminum, and magnesium, that are capable of dissolving in the solvents contained in the
precursor solution. Additive components may also include stoichiometric excesses of
soluble compounds included in the precursor solution. For example, soluble yttrium salts
or soluble copper salts may be included in the precursor solution in excess of that required
"To form YBCO. Insoluble admtive~c6~mpOnentS" can also be added totlie precursor - — -
solution.
Examples of metal salt solutions that can be used are as follows.
In some embodiments, the metal salt solution can have a relatively small amount of
free acid. In aqueous solutions, this can correspond to a metal salt solution with a
relatively neutral pH (e.g., neither strongly acidic nor strongly basic). The metal salt
solution can be used to prepare multi-layer superconductors using a wide variety of
materials that can be used as the underlying layer on which the superconductor layer is
formed.
The total free acid concentration of the metal salt solution can be less than about
lxlO'3 molar (e.g., less than about lxlO"5 molar or about lxlO"7 molar). Examples of free
acids that can be contained in a metal salt solution include trifluoroacetic acid, acetic acid,
nitric acid, sulfuric acid, acids of iodides, acids of bromides and acids of sulfates.
When the metal salt solution contains water, the precursor composition can have a
pH of at least about 3 (e g, at least about 5 or about 7)
In some embodiments, the metal salt solution can have a relatively low water
content (e.g., less than about 50 volume percent water, less than about 35 volume percent
water, less than about 25 volume percent water)

In embodiments in which the metal salt solution contains trifluoroacetate ion and
an alkaline earth metal cation (e.g., barium), the total amount of trifluoroacetate ion can be
selected so that the mole ratio of fluorine contained in the metal salt solution (e.g., in the
form of trifluoroacetate) to the alkahne earth metal (e.g , barium ions) contained in the
metal salt solution is at least about 2.1 (e.g., from about 2-1 to about 18.5:1, or from about
2:1 to about 10:1).
In general, the metal salt solution can be prepared by combining soluble
compounds of a first metal (e g., copper), a second metal (e g, an alkahne earth metal),
and a rare earth metal with one or more desired solvents and optionally water As used
herein, "soluble compounds" of the first, second and rare earth metals refer to compounds
of these metals that are capable of dissolving in the solvent(s) contained in the metal salt
solution. Such compounds include, for example, salts (e.g., nitrates, acetates, alkoxides,
iodides, sulfates and trifluoroacetates), oxides and hydroxides of these metals
In certain embodiments, a metal sail solution can be formed of an organic solution
'" "containing metal" tnffuoroacetates" prepared from powders of Ba(C2CCH3)2, Y(ChCCH3)3, - -
and Cu(C>2CCH3)2 which are combined and reacted using methods known to those skilled
in the art. For example, the metal trifluoroacetate powders can be combined in a 2-l-3
ratio in methyl alcohol to produce a solution substantially 0.94 M based on copper content.
In certain embodiments, the metal salt solution can contain a Lewis base. The rare
earth metal can be yttrium, lanthanum, europium, gadolinium, terbium, dysprosium,
holmium, erbium, thulium, ytterbium, cenum, praseodymium, neodymium, promethium,
samarium or lutetium. In general, the rare earth metal salt can be any rare earth metal salt
that is soluble rn the solvent(s) contained in the metal salt solution and that, when being
processed to form an intermediate (e.g , a metal oxyhaude intermediate), forms rare earth
oxide(s) (e.g., Y2O3). Such salts can have, for example, the formula M(02C-(CH2)n-
CXX/X'')(02C-(CH2)m-CXmX''''X',"')(02C-(CH2)p-CX'''"'X"'''''X'''''''') or M(OR)3. M is
the rare earth metal, n, m and p are each at least one but less than a number that renders
the salt insoluble in the solvent(s) (e g., from one to ten). Each of X, X', X", X'", X"",
X'"", X""", X'""" and X"""" is H, F, CI, Br or I. R is a carbon containing group, which
can be halogenated (e.g., CH2CF3) or nonhalogenated. Examples of such salts include
nonhalogenated carboxylates, halogenated acetates (e.g., trifluoroacetate, tnchloroacetate,
tribromoacetate, tniodoacetate), halogenated alkoxides, and nonhalogenated alkoxides.
Examples of such nonhalogenated carboxylates include nonhalogenated actetates (e g ,

M(02C-CH3)3). The alkaline earth metal can be barium, strontium or calcium. Generally,
the alkaline earth metal salt can be any alkaline earth metal salt that is soluble in the
solvent(s) contained in the metal salt solution and that, when being processed to form an
intermediate (e.g , a metal oxyhahde intermediate), forms an alkaline earth halide
compound (e.g., BaF2, BaCl2, BaBr2, Bali) prior to forming alkaline earth oxide(s) (e.g ,
BaO). Such salts can have, for example, the formula M'(02C-(CH2)irCXX'X")(02C-
(CH2)m-CX'"X""X'"") or M'(OR)2. M' is the alkaline earth metal n and m are each at
least one but less than a number that renders the salt insoluble in the solvent(s) (e.g., from
one to ten). Each of X, X', X", X'", X"" and X'"" is H, F, CI, B or, I. R can be a
halogenated or nonhalogenated carbon containing group. Examples of such salts include
halogenated acetates (e.g., trifhioroacetate, txichloroacetate, tribromoacetate,
triiodoacetate). Generally, the transition metal is copper The transition metal salt should
be soluble in the solvent(s) contained in the metal salt solution. Preferably, during
conversion of me precursor to the intermediate (e g., metal oxyhahde), minimal cross- '
linking occurs between discrete transition metal molecule;, (e.g., copper molecules)- Such
transition metals salts can have, for example, the formula M"(CXX'X"-CO(CH)aCO-
CX"rX""X""')(CX"""X""'"X"""" CO(CH)bCO CX"'"""X"""""X","""")1 M"(02C-(CH2)n-
-CXX'X") (02C-(CH2)m-CX"'X""X"'") or M"(OR)2 M" is the transition metal a and b
are each at least one but less than a number that renders the salt insoluble m the solvent(s)
(e.g., from one to five). Generally, n and m are each at least one but less than a number
that renders the salt insoluble in the solvent(s) (e g., from one to ten). Each of X, X', X",
X'", X"", X'"", X""", X'""", X"""", X'"""", X""""", X'""""" is H, F, CI, Br or I. R is a
carbon containing group, which can be halogenated (e.g., CH2CF3) or nonhalogenated.
These salts include, for example, nonhalogenated actetates (e.g., M"(02C-CH3)2),
halogenated acetates, halogenated alkoxides, and nonhalogenated alkoxides. Examples of
such salts mclude copper trichloroacetate, copper tribromoacetate, copper triiodoacetate,
Cu(CH3COCHCOCF3)2, Cu(OOCC7Hi5)2, Cu(CF3COCHCOF3)2,
Cu(CH3COCHCOCH3)2, Cu(CH3CH2C02CHCOCH3)2, CuO(C5H6N)2 and Cu303Ba2(0-
CH2CF3)4. In certain embodiments, the transition metal salt is a carboxylate salt (e.g., a
nonhalogenated carboxylate salt), such as a propionate salt of the transition metal (e.g , a
nonhalogenated propionate salt of the transition metal). An example of a nonhalogenated
propionate salt of a transition metal is Cu(02CC2H5)2. In some embodiments, the
transition metal salt is a simple salt, such as copper sulfate, copper nitrate, copper iodide

and/or copper oxylate. In some embodiments, n and/or m can have the value zero. In
certain embodiments, a and/or b can have the value zero. An illustrative and nonlimiting
list of Lewis bases includes nitrogen-containing compounds, such as ammonia and amines.
Examples of amines include CH3CN, C5H5N and R1R2R3N. Each of Ri R2 R3 is
independently H, an alkyl group (e.g., a straight chained alkyl group, a branched alkyl
group, an aliphatic alkyl group, a non-aliphatic alkyl group and/or a substituted alkyl
group) or the like. Without wishing to be bound by theory, it is believed that the presence
of a Lewis base in the metal salt solution can reduce cross-linking of copper during
intermediate formation. It is believed that this is achieved because a Lewis base can
coordinate (e.g., selective coordinate) with copper ions, thereby reducing the ability of
copper to cross-link.
Typically, the metal salt solution is applied to a surface (e.g., a buffer layer
surface), such as by spin coating, dip coating, web coating, slot coating, gravure coating,
or other techniques known to those skilled in the art, and subsequently heated
' At a subsequent station 940, Qie precursor components aie decomposed. In the - --
case of precursor components including at least one fluoride-containing salt, the first step
of the heating step is performed to decompose the metalorganic molecules to one or more
oxyfluoride intermediates of the desired superconductor material
Typically, the initial temperature m this step is about room temperature, and the
final temperature is from about 190°C to about 210°C, preferably to a temperature to
about 200°C. Preferably, this step is performed using a temperature ramp of at least about
5°C per minute, more preferably a temperature ramp of at least about 10°C per minute,
and most preferably a temperature ramp of at least about 15°C per minute. During this
step, the partial pressure of water vapor in the nominal gas envnonment is preferably
maintained at from about 5 Torr to about 50 Torr, more preferably at from about 5 Torr to
about 30 Torr, and most preferably at from about 20 Torr to about 30 Torr. The partial
pressure of oxygen in the nominal gas environment is maintained at from about 0 1 Torr to
about 760 Torr and preferably at about 730 - 740 Torr
Heating is then continued to a temperature of from about 200°C to about 290°C
using a temperature ramp of from about 0.05°C per minute to about 5°C per minute (e g ,
from about 0.5°C per minute to about 1°C per minute). Preferably, the gas environment
during this heating step is substantially the same as the nominal gas environment used

when the sample is heated to from the initial temperature to from about 190°C to abtfut
215°C.
Heating is further continued to a temperature of about 650°C, or more preferably to
a temperature of about 400°C, to form the oxyfluonde intermediate. This step is
preferably performed using a temperature ramp of at least about 2°C per minute, more
preferably at least about 3°C per minute, and most preferably at least about 5°C per
minute. Preferably, the gas environment during this heating step is substantially the same
as the nominal gas environment used when the sample is heated to from the initial
temperature to from about 190°C to about 215°C.
In alternate embodiments, barium fluoride is formed by heating the dried solution
from an initial temperature (e g., room temperature) to a temperature of from about 190°C
to about 215°C (e.g., about 210°C) in a water vapor pressure of from about 5 Torr to about
50 Torr water vapor (e.g , from about 5 Torr to about 30 Torr water vapor, or from about
10 Torr to about 25 Torr water vapor) The nominal partial pressure of oxygen can be, for
• example,^T-om-about-O.l Torr to about 760 Torr In these embodiments, heating is then-
continued to a temperature of from about 220°C to about 290°C (e.g, about 220°C) in a
water vapor pressure of from about 5 Torr to about 50 Torr water vapor (e.g., from about 5
Torr to about 30 Torr water vapor, or from about 10 Torr to about 25 Torr water vapor).
The nominal partial pressure of oxygen can be, for example, from about 0.1 Torr to about
760 Torr. This is followed by heating to about 400°C at a rate of at least about 2°C per
minute (e.g., at least about 3°C per minute, or at least about 5CC per minute) in a water
vapor pressure of from about 5 Torr to about 50 Torr water vapor (e.g., from about 5 Torr
to about 30 Torr water vapor, or from about 10 Torr to about 25 Torr water vapor) to form
barium fluoride The nominal partial pressure of oxygen can be, for example, from about
0.1 Torr to about 760 Torr
In certain embodiments, heating the dried solution to form barium fluoride can
include putting the coated sample in a pre-heated furnace (e.g., at a temperature of at least
about 100°C, at least about 150°C, at least about 200°C, at most about 300°C, at most
about 250°C, about 200°C) The gas environment in the furnace can have, for example, a
total gas pressure of about 760 Torr, a predetermined partial pressure of water vapor (e.g.
at least about 10 Torr, at least about 15 Torr, at most about 25 Torr, at most about 20 Torr,
about 17 Torr) with the balance bemg molecular oxygen. After the coated sample reaches
the furnace temperature, the furnace temperature can be increased (e.g., to at least about

225°C, to at least about 240°C, to at most about 275°C, to at most about 260°C, about
250°C) at a predetermined temperature ramp rate (e g., at least about 0.5°C per minute, at
least about 0.75°C per minute, at most about 2°C per minute, at most about 1.5°C per
minute, about 1°C per minute). This step can be performed with the same nominal gas
environment used in the first heating step. The temperature of the furnace can then be
further increased (e.g., to at least about 350°C, to at least about 375°C, to at most about
450°C, to at most about 425°C, about 450°C) at a predetermined temperature ramp rate
(e.g., at least about 5°C per minute, at least about 8°C per minute, at most about 20°C per
minute, at most about 12°C per minute, about 10°C per minute). This step can be
performed with the same nominal gas environment used in the first heating step.
The foregoing treatments of a metal salt solution can result in an oxyfluoride
intermediate film in which the constituent metal oxides and metal fluorides are
homogeneously distributed throughout the film Preferably, the precursor has a relatively
low defect density and is essentially free of cracks through the intermediate thickness.
While-solution chemistry for- barium fluoride formation -has been disclosed, other methods - ~
can also be used for other precursor solutions
The superconductor intermediate film can then be heated to form the desired HTS
layer at a further processing station 1050 Typically, this step is performed by heating
from about room temperature to a temperature of from about 700°C to about 825°C,
preferably to a temperature of about 740°C to 800°C and more preferably to a temperature
of about 750°C to about 790°C, at a temperature ramp of about greater than 25°C per
minute, preferably at a temperature rate of about greater than 100°C per minute and more* .
preferably at a temperature rate about greater than 200°C per minute This step can also
start from the final temperature of about 400 - 650°C used to form the intermediate
oxyfluoride film. During this step, a process gas is flowed over the film surface to supply
the gaseous reactants to the film and to remove the gaseous reaction products from the
film. The nominal gas environment during this step has a total pressure of about 0.1 Torr
to about 760 Torr and is comprised of about 0 09 Torr to about 50 Torr oxygen and about
0.01 Torr to about 150 Torr water vapor and about 0 Torr to about 750 Torr of an inert gas
(nitrogen or argon). More preferably, the nominal gas environment has a total pressure of
about 0.15 Torr to about 5 Torr and is comprised of about 0.1 Torr to about 1 Torr oxygen
and about 0.05 Torr to about 4 Torr water vapor

The film is then held at a temperature of about 700°C - 825°C, preferably to a
temperature of about 740°C to 800°C and more preferably to a temperature of about 750°C
to about 790°C, for a time of about at least 5 minutes to about 120 minutes, preferably for
a time of at least about 15 minutes to about 60 minutes, and more preferably for a time of
at least about 15 minutes to about 30 minutes. During this step, a process gas is flowed
over the film surface to supply the gaseous reactants to the film and to remove the gaseous
reaction products from the film. The nominal gas environment during this step has a total
pressure of about 0.1 Torr to about 760 Ton and is comprised of about 0.09 Torr to about
50 Torr oxygen and about 0.01 Torr to about 150 Torr water vapor and about 0 Torr to
about 750 Torr of an inert gas (nitrogen or argon) More prefeiably, the nominal gas
environment has a total pressure of about 0.15 Torr to about 5 Torr and is comprised of
about 0.1 Torr to about 1 Torr oxygen and about 0.05 Torr to about 4 Torr water vapor.
The film is then cooled to ioom temperature in a nominal gas environment with an
oxygen pressure of about 0.05 Torr to about 150 Torr, preferably about 0.1 Torr to about
0.5 Torr and more"preferably from about 0.1 Torr to about 0 2 Torr.
Optionally, filamentization can be performed at station 1060 by known processes,
or by processes described in U S. Patent Application 10/955,801, filed on September 29,
2004. Further processing by noble metal deposition at station 1070, oxygen annealing at
station 1080, and slitting at station 1090 complete the process.
Example 1. Preparation of a multilayer conductor from double coated
superconducting layers with different compositions
A baseline YBCO precursor solution havmg a stoichiometry of Y:Ba:Cu of
1 2:3.23 was prepared by dissolving about 0 85 grams Y(CF3C02)3, about 1.45 grams of
Ba(CF3C02)2 and about 1.35 grams of Cu(C2H5C02)2 in about 4.85 mL of methanol
(CH3OH) and about 0.15 mL of propionic acid (C2H6CO2) The final volume of the
solution was adjusted to about 5 mL with methanol.
A baseline YBCO precursor solution with 50% dysprosium addition having a
stoichiometry of Y:Dy :Ba:Cu of 1 0 5'2.3.23 was piepared by dissolving about 1.70
grams Dy(CH3C02)3, and about 1 90 mL of methanol (CH3OH) in about 20 mL of
baseline solution. The final volume of the solution was adjusted to about 25 mL with
baseline solution.
1.2M Cu(C2H5C02)2 solution was made by dissolving 1.24g of Cu(C2H5C02)2
powder in 4.85ml of methanol and 0.15ml of C2H5C02H.

The 50% Dy added precursor solution was deposited on a biaxially textured oxide
buffered metallic substrate with the structure Ni(5at%)WAr203/YS27Ce02by slot the coating technique. The solution was coated on the buffered substrate with the amount
targeted to form a 0.8 \xm thick REBa2Cu307.x film.
The coated sample was decomposed to an intermediate metal oxyfiuoride film by
heating, in a 2.25" diameter tube furnace, from room temperature to about 200°C at a rate
of about 15°C per minute, then from about 200°C to about 250 C at a rate of about 0 9°C
per minute and then from about 250°C to about 400°C at a rate of about 5°C per minute in
a flowing gas environment having a total gas pressure of about 760 Torr (water vapor
pressure of about 24 Torr and balance oxygen)
The metal oxyfiuoride film was then coated with Cu^HsCC^ solution with
targeted thickness of 0.1 |im. The coated film was dried at 95°C through a heated tunnel
The dried film was then coated again with baseline solution prepared as mentioned earlier
with target final thickness of 0.6 |im YBa2Cu3Ox
- - - Coated tape was decomposed again to form the intermediate metal oxyfiuoride by - -
the same process as mentioned earlier except this time the H2O vapor pressure was
controlled to about 6 5 Torr.
The decomposed tape was heat treated to form an oxide superconductor The tape
was joined with 4 m of similarly coated NiW leader tape both m front and in the back to
establish the uniform and control environment dunng the reaction. The tape was then
reacted ar 785°C with the following parameters The tape was ramped up to 785°C with
average ramp rate of about 520°C/min During reaction, the total pressure during reaction
was controlled to about 1 Torr. The H20 partial pressure was about 800 mTorr and
oxygen partial pressure was about 200 mTorr. The reaction time was about 11 mm.
During cooling, a total pressure of about 1 Torr was used with oxygen partial pressure at
about 200 mTorr and N2 partial pressure at about 800 mTorr
The reacted film was coated on both sides with 3 u.111 of Ag protection layer and
then annealed in a 760 Torr oxygen environment The resulting film earned a critical
current of about 350A/cm-widm or a critical current density of about 2.5MA/cm2 at 77K,
self field
The Ag coated 4 cm wide tape, which was nominally 4 m long, was slit into eight
4.1 mm wide strips using a roll slitter. These wires are referred to as "insert wires". Two

adjacent insert wires from one side of the 4 cm wide strip, channels 1 and 2, were then
solder laminated together with copper lamina
The two insert wires were oriented so the Ag face covering the superconducting
layer was facing away from each other This orientation places the surfaces with the Ag
face near the NiW substrate together. Continuous reel-to-reel solder lamination was used
to form the 4-ply article. The lamination process joined 2 copper lamina to 2 insert wires
using used a bath of 36Pb-62Sn-2Ag solder with a melting pomt of 179°C operating at
225°C and 4 m/min. The UNS type C15500 copper lamina was 4.3 mm wide and
nominally 0.050 mm thick. The insert wires were 4.1 mm wide and nominally 0 083 mm
thick Both surfaces of each of the 4 lamina are fluxed in-line and wet to the solder before
being aligned and pulled through a the in the lamination process. The final 4-ply article
was nominally 4.3 wide and 0.27 mm thick The critical current at 77K, self field
measured in 0.5 m segments over 2 m was 237, 240, 239, and 235 Amperes, respectively.
Incorporation By Reference
The following documents are hereby incorporated by reference U S. Patent No
5,231,074, issued on July 27, 1993, and entitled "Preparation of Highly Textured Oxide
Superconducting Films from MOD Precursor Solutions," U S Patent No. 6,022,832,
issued February 8, 2000, and entitled "Low Vacuum Process for Producing
Superconductor Articles with Epitaxial Layers," U.S. Patent No. 6,027,564, issued
February 22,2000, and entitled "Low Vacuum Process for Producing Epitaxial Layers,"
U.S. Patent No. 6,190,752, issued February 20, 2001, and entitied "Thin Films Having
Rock-Salt-Like Structure Deposited on Amorphous Surfaces,' PCT Publication No WO
00/58530, published on October 5, 2000, and entitled "Alloy Materials," PCT Publication
No WO/58044, published on October 5, 2000, and entitled "Alloy Materials," PCT
Publication No. WO 99/17307, published on April 8, 1999, and entitled "Substrates with
Improved Oxidation Resistance," PCT Publication No. WO 99/16941, published on April.
8,1999, and entitled "Substrates for Superconductors," PCT Publication No. WO
98/58415, published on December 23, 1998, and entitled "Controlled Conversion of Metal,
Oxyfluorides into Superconducting Oxides," PCT Publication No. WO 01/11428,
published on February 15, 2001, and entitled "Multi-Layer Articles and Methods of
Making Same," PCT Publication No WO 01/08232, published on February 1, 2001, and
entitled "Multi-Layer Articles And Methods Of Making Same," PCT Publication No. WO

01/08235, published on February 1, 2001, and entitled "Methods And Compositions For
Making A Multi-Layer Article," PCT Publication No WO 01/08236, published on
February 1, 2001, and entitled "Coated Conductor Thick Film Precursor", PCT
Publication No. WO 01/08169, published on February 1, 2001, and entitled "Coated
Conductors With Reduced A.C Loss" PCT Publication No. WO 01/15245, published on
March 1, 2001, and entitled "Surface Control Alloy Substrates And Methods Of
Manufacture Therefor," PCT Publication No WO 01/08170, published on February 1',
2001, and entitled "Enhanced Purity Oxide Layer Formation," PCT Publication No. WO
01/26164, published on April 12, 2001, and entitied "Control of Oxide Layer Reaction
Rates," PCT Publication No. WO 01/26165, published on April 12, 2001, and entitled
"Oxide Layer Me&od," PCT Publication No. WO 01/08233, published on February 1,
2001, and entitled "Enhanced High Temperature Coated Superconductors," PCT
Publication No. WO 01/08231, published on February 1, 2001, and entitled "Methods of
Making A Superconductor," PCT Publication No WO 02/35615, published on April 20,
-2002, and entitled "Precursor Solutions and Methods of Using Same," U S.-Patent --- - —
Application Serial No. 09/579,193, filed on May 26, 2000, and entitled, "Oxide Bronze
Compositions And Textured Articles Manufactured In Accordance Therewith;" and U S.
Provisional Patent Application Serial No. 60/309,116, filed on July 31, 2001, and entitled
"Multi-Layer Superconductors And Methods Of Making Same;" U.S Patent Application
Serial No. 10/208,134, filed on July 30, 2002, and entitled "Superconductor Methods and
" Reactor;" and U.S. Provisional Patent Application Serial No 60/308,957, filed on July 31,
2001, and entitled "Superconductor Methods and Reactors;" and U.S. Provisional Patent ■
Application Serial No. 60/166,297, filed on Nov 18,1999, and entitled "Superconductor
Articles and Compositions and Methods for Making Same;" and commonly owned U.S.
patent application Ser. No. 09/615,999, filed on July 14, 2000, and entitled
"Superconductor Articles and Compositions and Methods for Making Same;" and U.S.
Provisional Application No. 60/477,613, filed June 10, 2003, and entitled "Superconductor
Methods and Reactors;" and U.S. Utility Application No. 10/858,309, filed June 4, 2004,
and entitled "Superconductor Methods and Reactors;" and U.S. Patent Appbcation Serial
No. 10/955,875, filed on September 29, 2004, and entitled "Low AC Loss Filamentary
Coated Superconductors;" and U S. Patent Appbcation 10/955,801, filed on September 29,
2004, and entitled "Stacked Filamentary Superconductors;" and U.S. Provisional Patent
Application Serial No. 60/667,001, filed on March 31, 2005, and entitled "Mesh-Type

Stabilizer for Filamentary Coated Superconductors;" and U.S. Patent Application No
(TBA), filed on an even date herewith, and entitled "High Temperature Superconducting
Wires and Coils," all of which are hereby incorporated by reference.
What is claimed is:

WE CLAIM :
1. A laminated superconductor wire, comprising:
a superconductor wire assembly, said assembly having a length and a width,
said assembly comprising:
a first superconductor insert comprising a first high temperature
superconductor layer overlaying a first biaxially textured substrate and a first
electrically conductive cap layer overlaying and in electrical contact with the first
superconductor layer, and
a second superconductor insert comprising a second high temperature
superconductor layer overlaying a second biaxially textured substrate and a second
electrically conductive cap layer overlaying and in electrical contact with the second
superconductor layer,
wherein the first and second superconductor inserts are stacked and joined
together at their respective biaxially textured substrates; and an electrically conductive
structure substantially surrounding the superconductor wire assembly, wherein the
electrically conductive structure is in electrical contact with the each of the
electrically conductive cap layers.
2. The wire as claimed in claim 1, wherein the first and second superconductor
layers comprise a rare earth-alkaline earth-copper oxide.
3. The wire as claimed in claim 2, having a first buffer layer interposed between
the first superconductor layer and the first substrate, and a second buffer layer
interposed between the second superconductor layer and the second substrate.
4. The wire as claimed in claim 1, wherein a bonding material bonds the first
substrate and second substrate together.

5. The wire as claimed in claim 4, wherein the bonding material comprises a
material selected from the group of electrically conductive materials and electrically
nonconductive materials.
6. The wire as claimed in claim 4, wherein the first biaxially textured substrate
and second biaxially textured substrate have surfaces that are treated to provide
electrical contact between the biaxially textured substrates.
7. The wire as claimed in claim 4, wherein the bonding material comprises at
least one layer of a conductive material and at least one layer of a nonconductive
material.
8. The wire as claimed in claim 4, wherein the first biaxially textured substrate
has a first wetting layer disposed on the opposite surface of the biaxially textured
substrate that the first HTS layer overlays, and the second biaxially textured substrate
has a second wetting layer disposed on the opposite surface of the biaxially textured
substrate that the second HTS layer overlays, and wherein the first wetting layer and
the second wetting layer bond the first and second biaxially textured substrates
together.
9. The wire as claimed in claim 4, wherein the electrically conductive structure
comprises:
a first conductive strip and a second conductive strip, wherein the
superconductor wire assembly is interposed between and is in electrical contact with
the first and second conductive strips; and
a substantially nonporous electrically conductive filler, wherein the filler
extends between the first and second conductive strips along the length of the
superconductor wire assembly.

10. The wire as claimed in claim 9, wherein the first and second conductive strips
comprise a metal independently selected from the group of aluminum, copper, silver,
nickel, iron, stainless steel, aluminum alloy, copper alloy, silver alloy, nickel alloy,
and iron alloy.
11. The wire as claimed in claim 9, wherein the first and second conductive strips
have a width that is greater than the width of the superconductor wire assembly.
12. The wire as claimed in claim 11,, wherein the width of the first and second
conductive strips is between 0.01 and 2 mm greater than the width of the
superconductor wire assembly.
13. The wire as claimed in claim 9, wherein the first and second conductive strips
have a thickness between 0.01 and 2 mm.

14. The wire as claimed in claim 9, wherein the substantially nonporous
electrically conductive filler has a thickness between 0.005 and 1mm along a side of
the superconductor wire assembly.
15. The wire as claimed in claim 9, wherein the substantially nonporous
electrically conductive filler comprises a material selected from the group of solder,
metal, metal alloy, metal amalgam, and conductive polymer.

16. The wire as claimed in claim 9, wherein the bonding material comprises the
substantially nonporous electrically conductive filler.
17. The wire as claimed in claim 9, having a layer of conductive material
substantially surrounding the superconductor wire assembly.

18. The wire as claimed in claim 17, wherein the layer of conductive material is
selected from the group of metal, electrically conductive polymer, polymer filled with
fine metal powder, and conductive glue.
19. The wire as claimed in claim 9, wherein the electrically conductive structure
comprises:
an electrically conductive layer that partially surrounds and is in electrical
contact with the superconductor wire assembly along at least three sides; and
a substantially nonporous electrically conductive filler, wherein the filler
substantially surrounds the superconductor wire assembly and bonds it to the
conductive layer.
20. The wire as claimed in claim 19, wherein the electrically conductive layer
comprises a metal selected from the group of aluminum, copper, silver, nickel, iron,
stainless steel, aluminum alloy, copper alloy, silver alloy, nickel alloy, and iron alloy.
21. The wire as claimed in claim 19, wherein the electrically conductive layer has
a thickness between 0.0001 and 1 mm.

22. The wire as claimed in claim 19, wherein the substantially nonporous
electrically conductive filler substantially fills voids in the superconductor wire
assembly and between the superconductor wire assembly and the conductive layer.
23. The wire as claimed in claim 19, wherein the substantially nonporous
electrically conductive filler comprises a material selected from the group of solder,
metal, metal alloy, metal amalgam, and conductive polymer.

24. The wire as claimed in claim 19, wherein the layer of conductive material is
selected from the group of metal, electrically conductive polymer, polymer filled with
fine metal powder, and conductive glue.
25. The wire as claimed in claim 9, wherein the electrically conductive structure
comprises an electrically conductive material substantially surrounding and in
electrical contact with the superconductor wire assembly.
26. The wire as claimed in claim 25, wherein the electrically conductive material
comprises a material selected from the group of electrically conductive polymer,
polymer filled with fine metal powder, and conductive glue.
27. The wire as claimed in claim 25, wherein the electrically conductive material
comprises a conductive foil wrapped around said superconductor wire assembly.
28. The wire as claimed in claim 27, wherein the conductive foil comprises a metal
selected from the group of aluminum, copper, silver, nickel, iron, stainless steel,
aluminum alloy, copper alloy, silver alloy, nickel alloy, and iron alloy.
29. The wire as claimed in claim 28, having at least one layer of a substantially
nonporous material substantially surrounding the conductive foil.
30. The wire as claimed in claim 29, wherein the substantially nonporous material
is selected from the group of solder, electrically conductive polymer, polymer filled
with fine metal powder, conductive glue, and electrically nonconductive polymer.

31. A method of making a laminated superconductor wire, the method
composing:
providing a superconductor wire assembly, said assembly having a length
and a width, said assembly comprising :
a first superconductor insert having a first high temperature
superconductor layer overlaying a first biaxially textured substrate and a first
electrically conductive cap layer overlaying and in electrical contact with the first
superconductor layer, and a second superconductor insert having a second high
temperature superconductor layer overlaying a second biaxially textured substrate and
a second electrically conductive cap layer overlaying and in electrical contact with the
second superconductor layer,
wherein the first and second superconductor inserts are stacked and
joined together at their respective biaxially textured substrates; and simultaneously
laminating the first and second high temperature superconductor inserts to
corresponding first and second conductive strips with a substantially nonporous
electrically conductive filler, and
depositing additional filler between the first and second conductive strips
along the length of the superconductor wire assembly, such that the first and second
conductive strips and the filler together form an electrically conductive structure that
substantially surrounds the superconductor wire assembly wherein the electrically
conductive structure is in electrical contact with the each of the electrically conductive
cap layers.
32. The method as claimed in claim 31, which involves providing a bonding
material between the first and second substrate.
33. The method as claimed in claim 32, which involves providing first and second
wetting layers on a surface of the corresponding first and second substrates opposite
the high temperature superconductor layer

34. The method as claimed in claim 31, which involves providing a first buffer
layer interposed between the first superconductor layer and the first substrate, and a
second buffer layer interposed between the second superconductor layer and the
second substrate.
35. The method as claimed in claim 34, which involves providing a first
electrically conductive cap layer interposed between the first superconductor layer
and the first conductive strip, and a second electrically conductive cap layer
interposed between the second superconductor layer and the second conductive strip.
36. A superconductor wire assembly comprising:
a first superconductor insert comprising:
a first biaxially textured substrate;
a first high temperature superconductor layer overlaying the first biaxially
textured substrate; and
a cap layer overlaying the first high temperature superconductor layer;
a second superconductor insert comprising:
a second biaxially textured substrate;
a second high temperature superconductor layer overlaying the second
biaxially textured substrate; and
a cap layer overlaying the second high temperature superconductor layer;
wherein the first and second superconductor inserts are stacked and joined
together at their respective substrates and an electrically conductive structure
substantially surrounding the superconductor wire assembly, wherein the electrically
conductive structure is in electrical contact with the each of the electrically conductive
cap layers.

37. The wire assembly as claimed in claim 36, having a first buffer layer
interposed between the first superconductor layer and the first substrate, and a second
buffer layer interposed between the second superconductor layer and the second
substrate.

ABSTRACT

LAMINATED SUPERCONDUCTOR WIRE AND METHOD OF MAKING SAME
The present invention relates to a laminated superconductor wire (200) , comprising a
superconductor wire assembly, said assembly having a length and a width, said assembly
comprising a first superconductor insert (210) comprising a first high temperature
superconductor layer overlaying a first biaxially textured substrate and a first electrically
conductive cap layer overlaying and in electrical contact with the first superconductor layer,
and a second superconductor insert (220) comprising a second high temperature
superconductor layer overlaying a second biaxially textured substrate and a second
electrically conductive cap layer overlaying and in electrical contact with the second
superconductor layer, wherein the first and second superconductor inserts (210,220) are
stacked and joined together at their respective biaxially textured substrates; and an
electrically conductive structure substantially surrounding the superconductor wire
assembly, wherein the electrically conductive structure is in electrical contact with the each
of the electrically conductive cap layers.