Technical Field
The present invention relates to metal composite
oxides with a novel crystal structure which exhibits an
ionic conductivity, and more particularly to a barium-
tungsten oxide with an ion channel formed for easy
movement of ions due to crystallographic specificity
resulting from the ordering of metal ion sites and metal
ion defects within a unit cell, and/or derivatives
thereof, ionic conductors including the oxides and an
electrochemical devices comprising the ionic conductors.
Background Art
Active studies have been made to ionic conductors
which are solid materials used as electrolytes in
electrochemical devices, such as gas sensors and fuel
cells. Major solid ionic conductors which have been
known to date can be classified according to their
crystal structures as shown in Table 1 [V.V.Kharton,
F.M.B.Marques,A,Atkinson, Solid State Ionics, 174 (2004)
135-149. P.Lacorre, F.Goutenoire, O.Bohnke, R.Retoux,
Y.Laligant, Nature, 404 (2000) 856-858. X.Turrillas,
A.P.Sellars, B.C.H.Steele, Solid State Ionics, 28-30
(1988) 465-469].
[Table 1]


All the materials listed in Table 1 have
potentials. However, each may be advantageous or
disadvantageous in certain applications because the
above materials exhibit different ionic conductivities
and physicochemical properties at various temperatures
due to their structural characteristics such as crystal
structures and ionic defect structures.
For example, in solid oxide fuel cell ("SOFC")
applications, it has been known that yttrium stabilized
zirconia ("YSZ") is the most suitable material for use
as a high-temperature SOFC electrolyte. However, a doped
ceria-type is more suitable for a low-temperature (lower
than 600°C) SOFC. In a high-temperature SOFC using any
other electrolyte (doped ceria or La0.8Sr0.2GaO3-δ) than
YSZ, materials such as La0.9Sr0.1AlO3-δ or Gd2Zr2O7 can be
used as a protective layer of a cathode. An ionic
conductor membrane for use in an oxygen pump should have
both electrical conductivity and ionic conductivity.
Accordingly, doped ceria, rather than YSZ with very low

electrical conductivity, is suitable to be used in an
oxygen pump. In addition, compounds having a cryolite
structure or LaYO3-type high-temperature oxygen ionic
conductors function as proton conductors at a wet
atmosphere and a low temperature.
Since various properties are required according to
the applications, it is very important to develop new-
type materials having ionic conductivity. If a new
material with a new crystal structure is developed,
thousands of derivatives can be synthesized and prepared
from the new material, which results in the rapid
development of relevant technologies.
Brief Description of the Drawings
The foregoing and other objects, features and
advantages of the present invention will become more
apparent from the following detailed description when
taken in conjunction with the accompanying drawings in
which:
FIG. 1 illustrates a unit cell structure of ABO3-
type perovskite;
FIG. 2 is a view showing an X-ray (Cu Kαl,
λ=1.5405Å) diffraction pattern ("XRDP") of a barium-
tungsten oxide (Ba11W4O23) prepared in Example 1;
FIG. 3 is a view comparing XRDP of Ba3WO6 with XRDP
of Ba11W4O23;
FIG. 4 is a Rietveld profile comparing XRDP of
Ba11W4O23 measured in Example 1 with a theoretical pattern
of a structural model;
FIG. 5 is a view showing an atom density map
(Fourier synthesis map) calculated by a neutron
diffraction analysis;
FIG. 6 is a view showing a crystal structure of

one layer on ab-cross section of a barium-tungsten oxide
(Ba11W4O23) prepared in Example 1;
FIG. 7 is a view showing a unit cell structure of
a barium-tungsten oxide (Ba11W4O23) prepared in Example 1;
FIG. 8 is a view showing oxygen ionic conductivity
of a barium-tungsten oxide (Ba11W4O23) of Example 1 at
various temperatures;
FIG. 9 is a view showing an X-ray (Cu Kα1,
λ=1.5405Å) diffraction pattern of a barium-strontium-
tungsten composite oxide (Ba10Sr1W4O23) prepared in
Example 3;
FIG. 10 is a view showing oxygen ionic
conductivity of a metal composite oxide (Ba11-xAxW4O24-d)
with A-site substituted according to the present
invention;
FIG. 11 is a view showing an X-ray (Cu Kα1,
λ=1.5405Å) diffraction pattern of a barium-tungsten-
tantalum composite oxide (Ba11W3Ta1O22.5) prepared in
Example 7;
FIG. 12 is a view showing oxygen ionic
conductivity of a metal composite oxide (Ba11W4-yByO24-d)
with B-site substituted according to the present
invention;
FIG. 13 is a view showing an X-ray (Cu Kα1,
λ =1.5405A) diffraction pattern of a barium-strontium-
tungsten-tantalum composite oxide (Ba10.5Sr0.5W3.5Ta0.5O22.75)
prepared in Example 8; and
FIG. 14 is a view showing oxygen ionic
conductivity of a metal composite oxide (Ba11-xAxW4-yByO24-d)
with A-site and B-site substituted according to the
present invention
Disclosure of the Invention

The inventors have discovered that a novel metal
composite oxide prepared by mixing barium and tungsten
at a specific ratio has a new crystal structure which
has not been known to date and exhibits oxygen ion
conductivity due to the new crystal structure. The
inventors have synthesized multiple derivative compounds
having the new crystal structure and analyzed ionic
conductivity of each derivative compound. The analysis
has revealed that oxygen ion conductivity is not an
inherent property of a barium-tungsten oxide but results
from the unique crystal structure with the ordered
arrangement of metal sites and metal defects within a
unit cell.
Therefore, it is an object of the present
invention to provide metal composite oxides having a new
crystal structure which exhibit ionic conductivities,
ionic conductors including the metal composite oxides
and electrochemical devices comprising the ionic
conductors.
The present invention provides metal composite
oxides with the new crystal structure, characterized by
conditions (a) to (c):
(a) Space group is Fd-3m (no. 227);
(b) Unit cell parameter is 17.0 ±1.0Å; and
(c) Crystallographic positions in the unit cell
occupied by cations with site occupancies as specified
in Table 2 (The crystallographic coordinates in the unit
cell are based on space group No. 227, origin choice 2
(p.701 of "International tables for crystallography",
vol. A, 5th ed. Kluwer Academic Publishers, 2002)) .
[Table 2]


The present invention also provides ionic
conductors including the above metal composite oxides
and electrochemical devices comprising the ionic
conductors.
Hereinafter, the present invention will be
explained in more detail.
The metal composite oxides according to the
present invention are single-phase compounds having the
previously unknown novel crystal structure. In other
words, the present invention provides single-phase metal
composite oxides having the novel crystal structure,
preferably, a barium-tungsten composite oxide and/or
derivatives thereof.
The metal composite oxides have a superstructure
formed by the ordering of metal defects on a perovskite
structure having a similar chemical formula, preferably,
on a cryolite structure, and thereby produces the
following effects.
1) Metal ions in the metal composite oxide
according to the present invention have a new metal
defect type which is distinguished from any known
disordered or ordered defect type. According to the
metal defect type of the present invention, metal ions
occupy 8b, 48f, 32e, 16d, 16c sites as specified in
Table 2, whereas metal defects exist at a specific site
in the unit cell (i.e., 8a site (1/8, 1/8, 1/8)). Due to
the ordering of a metal defect site (8a), an ion channel

for easy movement of ions is automatically induced so
that the metal composite oxide can function as an ionic
conductor showing conductivity according to the movement
of ions.
2) It is known that perovskite oxides generally
have both oxygen ionic conductivity and hydrogen ionic
conductivity in a moisture-containing atmosphere (T.
Norby, Solid State Ionics, 125 (1999) 1-11; I. Animitsa,
T. Norby, S. Marion, R. Glockner, A. Neiman, Solid State
Ionics, 145, (2001) 357-364). In view of this fact, it
is assumed that the metal composite oxides of the
present invention, which show oxygen ionic
conductivities through an ion channel induced therein,
may also allow hydrogen ions (protons) to easily move
through the ion channel and exhibit both oxygen ionic
conductivity and hydrogen ionic conductivity.
3) It will be demonstrated that the novel
crystal structure is not inherent only to a barium-
tungsten oxide but results from the ordered arrangement
of metal sites and metal defects within the unit cell.
Demonstration of this fact will basically change the
prediction and preparation of ionic conductive materials
through simple changes in compositions and components
generally performed in the art.
4) The present invention is the first
recognition of the fact that the ordering of metal
defects at 8a site, which renders the ionic conductivity
to the metal composite oxide, is the most important
factor of forming an ion channel. Through the analysis
and determination of the defect ordering, new crystal
structure materials having ionic conductivity could be
developed. Those materials may provide a basis for the
development of relevant technology.

In a metal composite oxide according to the
present invention, cations (metal ions) occupy the
crystallographic sites specified in Table 2. At the same
time, some anions in the metal composite oxide,
preferably, at least one anion, should have
crystallographic coordinates "96g (x,x,z) (0.40 ≤ x ≤
0.60, 0.59 ≤ z ≤ 0.66)" and a site occupancy "0 < 0 ≤
1". In addition, the site occupancy at 8a cation site
(1/8, 1/8, 1/8) should more preferably be 0 < 0. ≤ 1.
Most preferably, 8a site (1/8, 1/8, 1/8) should be
vacant. In other words, the site occupancy at 8a site
(1/8, 1/8, 1/8) should be zero. With a smaller occupancy
at 8a site, factors that may interrupt an ion conduction
channel can be reduced, thereby resulting in higher
ionic conductivity.
Preferably, the metal composite oxides according
to the present invention . should have the novel crystal
structure at a temperature above 100°C, i.e., within a
range of operating temperatures of an electrochemical
device. The temperature, however, is not limited to the
above range. The metal composite oxides can have the
novel crystal structure at a room temperature or a
higher temperature.
The metal composite oxides having the novel
crystal structure can be represented by chemical
formulae 1 to 4.



wherein,
A is at least one divalent element selected from
the group consisting of an alkaline earth metal, Cd, Sn,
Pb, Sm, Eu. Er, Tm and Yb;
A' is at least one element selected from the group
consisting of a monovalent alkali metal; a trivalent
rare earth element, Bi(III), Sb(III) or As(III); a
tetravalent rare earth element of Ce(IV), Pr(IV) Tb(IV),
Th(IV) or U(IV); and a cationic element of Zr(IV),
Hf(IV) or IIIB through VIA groups;
B is at least one hexavalent element selected from
the group consisting of VIA, VILA, VIII and VIB,
excluding oxygen;
B' is at least one element selected from the group
consisting of Li, Na, Mg, Ca, Sc, Y, rare earth elements
(elements No. 63 to 71) and elements of IIIB to VA
groups and having hexavalent or lower oxidation states;
C is at least one anion or H+ cation selected from
the group consisting of S, F and Cl; and
X is a decimal between 0 and 11 (0≤x≤11), y is a
decimal between 0 and 4 (0≤y≤4), z is a decimal between
0 and 8 (0≤z≤8), and 8 is a decimal between 0 and 6
(0≤δ≤6).
In formulae 1 to 4, A is preferably a combination
of at least one element selected from the alkaline earth
metal group consisting of Be, Mg, Ca, Sr, Ba and Ra,
more preferably a combination of Ba and Sr or Ba and Ca
having large-size ions.
In formulae 1 to 4, A' preferably includes at
least one of a monovalent element or a trivalent element
which is preferably at least one rare earth element
selected from the group consisting of La, Ce, Pr, Nd,

Sm, Eu and Gd. More preferably, the monovalent element
is K and the trivalent element is at least one of La, Gd
and Bi.
In formulae 1 to 4, B is. preferably at least one
element selected from the group consisting of W, Mo and
Cr. B' is preferably at least one element selected from
the group consisting of Nb, Ta, V and S with higher
reducibility.
In formulae 1 to 4, C is preferably an H+ cation
(proton). H+ (proton) present in the unit cell due to
the moisture H2O included in a wet atmosphere can easily
move through the ion channel explained above and
function as an ionic conductor.
The metal composite oxide represented by formulae
1 to 4 includes, but is not limited to, Ba11W4O23,
Ba10.5Sr0.5W4O23, Ba10Sr1W4O23, Ba10.5La0.5W4O23.25, Ba10La1W4O23.5,
Ba11W3.5Ta0.5O22.75, Ba11W3Ta1O22.5 or Ba10.5Sr0.5W3.5Ta0.5O22.75.
The metal composition oxides can be any compound having
the novel crystal structure explained above.
The metal composite oxides having the novel
crystal structure can be prepared by conventional
methods generally known in the art. For example, the
metal composite oxides can be prepared by mixing
precursor compounds each containing one or more elements
specified in formulae 1 to 4 at an appropriate molar
ratio, calcining the resulting mixture at a temperature
between 700°c and 1,700°C and then cooling the mixture.
Any salts containing one or more elements
specified in formulae 1 to 4 can be used as the
precursor compounds. There is no limitation in the molar
ratio of the precursor compounds. The precursor
compounds can be mixed together at an appropriate molar
ratio determined according to the object preparation.

Preferably, the mixture of the precursor compounds
is calcined at a temperature above 700°c, preferably
between 700°c and 1,700°C, for 5 to 72 hours.
For the calcination process, the following
conventional methods can be used: a first method of
forming the mixture in a pellet and calcining the
pellet; and a second method of calcining the mixture
itself. However, there is no limitation in using any
calcination method.
The calcined mixture is cooled to a room
temperature to obtain a single-phase metal composite
oxide having the novel crystal structure according to
the present invention (for example, a barium-tungsten
oxide and derivatives thereof). The cooling process can
be carried out at a room temperature. Alternatively, the
calcined mixture can be rapidly cooled using liquid
nitrogen or water at room temperature.
To define the crystallographic specificity of the
metal composite oxide prepared by the process explained
above, ABO3-type perovskite structure (FIG. 1) which is
similar to the crystal structure of the metal composite
oxide has been analyzed.
In the perovskite structure as shown in FIG. 1, a
metalion at B site is coordinated with oxygen atoms to
form an octahedron. Also, A-site metal ions are
coordinated with 12 oxygen atoms. When this ABO3-type
perovskite is multiplied by 8 and B site is substituted
with two types B and B' , resulting perovskite can be
represented by formula Aa (B4B'4)O24. When A and B are
transcribed as barium and B' is transcribed as tungsten,
the above formula will become Ba12W,O24 that represents a
generally known barium-tungsten oxide of a cryolite
structure type.

A metal composite oxide prepared according to the
present invention, for example, a barium-tungsten oxide
Ba11W4O23, was found to have barium and oxygen defects by
1/12 and 1/24 in the perovskite structure Bai2W4O24.
Also, in a crystallographic structure of BanW4O23,
ordering of the barium defect at the center of channel
in the tungsten (W(2)) polyhedron and formation of an
oxygen channel according to the barium defect were
observed (see FIG. 7) simultaneously. This is a new
crystal structure formed by the ordering of metal
defects in the generally known cryolite structure (Fm3m,
space group no. 225, unit cell parameter ~8.5Å).
The inventors have recognized and demonstrated for
the first time that the ordering of the metal defect
site (8a) indicated by Vu and Vd in FIG. 6 is the most
important factor of forming the oxygen channel.
The novel crystal structure of the metal composite
oxide prepared according to the present invention is
defined to have a space group Fd-3m (no. 227), a unit
cell parameter of about 17.0 ±1.0 A, metal sites (8b,
48f, 32e, 16d and 16c) occupied by metal ions and a
specific site (8a (1/8, 1/8, 1/8)) with metal defects.
The metal defect site automatically forms an ion channel
for easy movement of ions as shown in FIG. 7, regardless
of the metal ions forming the crystal structure. It is
possible to predict the ionic conductivity of the metal
composite oxide through such an ion conduction channel.
The inventors have also synthesized multiple
derivatives with various metals substituted and
performed experiments to confirm the ionic
conductivities of the derivatives. They have
demonstrated that the novel crystal structure explained
above is not. inherent only to a barium-tungsten oxide

but results from the ordered arrangement of metal sites
and metal defects within the unit cell.
The present invention provides ionic conductors
including metal composite oxides with the novel crystal
structure, preferably, oxygen- or proton-selective ionic
conductors.
Ionic conductors are materials that conduct
electricity with the movement of ions. Generally, ionic
conductors are used in a membrane type having a
separation factor that. selectively permeates one
element.
The ionic conductors according to the present
invention can be prepared using a conventional method
generally known in the art. For example, the ionic
conductor can be prepared by coating a conductive
electrode to apply an electric field. At this time, a
metal composite oxide of the present invention can be
used alone as an ionic conductor or mixed appropriately
with any other materials known in the art according to
purposes or applications.
In addition, the present invention provides
electrochemical devices comprising metal composite
oxides having the novel crystal structure as ionic
conductors.
The electrochemical devices can be any device for
performing electrochemical reactions, which includes,
but is not limited to, an oxygen probe, a fuel cell, a
chemical membrane reactor, an oxygen separation
membrane, an oxygen pump, a hydrogen separation
membrane, a hydrogen pump, a hydrogen gas sensor, a
steam sensor, a hydrocarbon sensor, a hydrogen
extraction, a hydrogen pressure controller, isotope
enrichment, tritium technology, steam electrolysis, H2S

electrolysis, HCl electrolysis, hydrogenation of
hydrocarbon, dehydrogenation, NH3 formation, an
electrochemical cell, an electrochromic device, a gas
sensor or a NOX trap.
The metal composite oxides included in the
electrochemical devices according to the present
invention, for example, a barium-tungsten oxide or a
derivative thereof, plays a role as an oxygen or proton
ionic conductor. Accordingly, the metal composite oxide
can be used for electrochemical filtration through a
porous filter, electrochemical treatment of a gas-state
efflux or heterogeneous catalysis. The metal composite
oxides can also be used in a chemical membrane reaction
of a reactor for controlling oxidation of hydrocarbon or
incorporated into an oxygen separation membrane. In
addition, the metal composite oxides can be used as an
electrolyte of a fuel cell that uses hydrogen as a fuel.
Best Mode for Carrying Out the Invention
Reference will now be made in detail to the
preferred embodiments of the present invention. It is to
be understood that the following examples are
illustrative only and the present invention is not
limited thereto.
[Examples 1 ~ 8] Metal composite oxide
Example 1
Barium carbonate (BaCO3) and a tungsten oxide (WO3)
were weighed and mixed at a metal-based molar ratio of
11:4. The resulting mixture was heated at a temperature
of 1,100°C for 20 hours. The heated mixture was cooled
to a room temperature and remixed to become a powder

state or form a pellet. The powder or pellet was heated
in air at 1,100°C for 10 hours and then rapidly cooled
using liquid nitrogen to complete the synthesis of a
barium-tungsten oxide (Ba11W4O23).

Example 2
A barium-strontium-tungsten composite oxide
(Ba10.5Sr10.5W4O23) was prepared in a similar way to Example
1, except that strontium Carbonate (SrCO3) was added to
barium carbonate (BaCO3) and tungsten oxide (WO3) and
mixed together at a metal-based molar ratio of
10.5:4:0.5 (BaCO3: WO3 : SrCO3) ,
Example 3
A barium-strontium-tungsten composite oxide
(Ba10Sr1W4O23) was prepared in a similar way to Example 1,
except that strontium Carbonate (SrCO3) was added to
barium carbonate (BaCO3) and tungsten oxide (WO3) and
mixed together at a metal-based molar ratio of 10:4:1
(BaCO3:WO3:SrCO3) .
Example 4
Ba10.5La0.5W4O23.25 was prepared in a similar way to
Example 1, except that lanthanum oxide (La2O3) was added
to barium carbonate (BaCO3) and tungsten oxide (WO3) and
mixed together at a metal-based molar ratio of
10.5:4:0.5 (BaCO3:WO3:La2O3).
Example 5
Ba10La1W4O23.5 was prepared in a similar way to
Example 1, except that lanthanum oxide (La2O3) was added

to barium carbonate (BaCO3) and tungsten oxide (WO3) and
mixed together at a metal-based molar ratio of 10:4:1
(BaCO3:WO3:La2O3).

Example 6
Ba11W3.5Ta0.5O22.75 was prepared in a similar way to
Example 1, except that tantalum oxide (Ta2O5) was added
to barium carbonate (BaCO3) and tungsten oxide (WO3) and
mixed together at a metal-based molar ratio of
11:3.5:0.5 (BaCO3: WO3:Ta2O5).
Example 7
Ba11W3Ta1O22.5 was prepared in a similar way to
Example 1, except that tantalum oxide (Ta2O5) was added
to barium carbonate (BaCO3) and tungsten oxide (WO3) and
mixed together at a metal-based molar ratio of ll:3:'l
(BaCO3:WO3:Ta2O5).

Example 8
Ba10.5Sr0.5W3.5Ta0.5O22.75 was prepared in a similar way
to Example 1, except that strontium carbonate (SrCO3) and
tantalum oxide (Ta2O5) were added to barium carbonate
(BaCO3) and tungsten oxide (WO3) and mixed together at a
metal-based molar ratio of 10.5:3.5:0.5:0.5 (BaCO3:WO3:
SrCO3:Ta2O5).

Experimental Example 1: Analysis of chemical
compositions of metal composite oxides (ICP-AES)
The chemical compositions of metal composite
oxides according to the present invention were analyzed
by ICP-AES (Inductively Coupled Plasma Atomic Emission
Spectroscope).
As samples, barium/tungsten-containing composite
oxides prepared in Examples 1 to 8 were used. Each
sample was pulverized, poured into a glass vial,
dissolved with a Conc. nitric acid and completely
decomposed using hydrogen peroxide. Each sample was
diluted to three different volumes and analyzed by a
standard method using ICP-AES (GDC Integra XMP).
ICP elementary analysis was performed on the
barium-tungsten oxide in Example 1. The results of
analysis showed that the molar ratio of barium to
tungsten is 11.00:4.00 (±0.02). The mole value of oxygen
was calculated to be 23 based on the oxidation number of
metal and the above molar ratio. Consequently, it was
confirmed that the barium-tungsten oxide in Example 1
can be represented by Ba11W4O23 which implies barium and
oxygen defects by 1/12 and 1/24 in known Ba12W4O24.
The metal composite oxides in Examples 2 to 8 were
analyzed in the same manner. Chemical compositions of
those metal composite oxides are specified in Table 3.
The results of analysis revealed that the metal
composite oxides in Example 2 to 8, like the metal
composite oxide in Example 1, are novel materials which
are different from conventional metal composite oxide.
Experimental Example 2: Analysis of the crystal
structure of metal composite oxides
The following analysis was performed to analyze

the crystallographic structures of the metal composite
oxides according to the present invention and
demonstrate that those metal composite oxides are novel
and distinguished from known barium-tungsten compounds.
2-1. Analysis of crystal structure using X-ray
diffraction pattern (XRDP) and neutron diffraction
pattern
As samples subject to diffraction analysis,
barium/tungsten-containing composite oxides as prepared
in Examples 1 to 8 were used.
Each sample was pulverized and filled in a sample
holder for X-ray powder diffraction. Each sample was
scanned using Bruker D8-Advance XRD with CuK α1
(λ =1.5405A) radiation at an applied voltage of 40kV and
an applied current of 50mA and with a step size of 0.02°.
A neutron diffraction analysis was carried out using
HANARO HRPD system (Korea Atomic Energy Research
Institute). Neutrons were scanned using 2 He-3 multi-
detector system and Ge(331) monochromator (λ =1.8361A)
with a step size of 0.05°.
In the X-ray diffraction pattern (XRDP) of the
barium-tungsten oxide prepared in Example 1, diffraction
peaks were observed and a unit cell parameter of
17.19±05Å was obtained from the positions of the peaks.
Indexing all peaks and observing the extinction rule in
this diffraction pattern, a space group of FD-3m (no.
227) was determined (see FIG. 2) . In addition, from this
diffraction pattern with all peaks indexed, it was
confirmed that the barium-tungsten oxide in Example 1 is
a pure single-phase without impurity.
The barium-strontium-tungsten composite oxide in
Example 3 (FIG. 9) , barium-tungsten-tantalum composite

oxide in Example 7 (FIG. 11) and barium-strontium-
tungsten-tantalum composite oxide in Example 8 (FIG. 14)
were analyzed in the same manner using X-ray diffraction
patterns (XRDP). The diffraction patterns showed that
the barium/tungsten-containing composite oxides in
Examples 2 to 8 have unit cell parameters in the same
range as the unit cell parameter of the barium-tungsten
oxide in Example 1 and the same space group as the
barium-tungsten oxide in Example 1. Thus, the metal
composite oxides of the present invention were all
turned out to be pure single phase.
The XRDP of Ba11W4O23 prepared in Example 1 was
compared with that of Ba3WO5 (Ba12W4O24) known in the art.
While one peak was observed in Ba11W4O23 at a main highest
peak angle between 2 9 and 30 degrees, two peaks were
observed in Ba3WO6 at the same angle (see FIG. 3) . This
is a clear evidence that the two compounds Ba11W4O23 and
Ba3WO6 have different structures.

2-2. Setting and analysis of a structural model
To determine the crystal structure of the metal
composite oxides of the present invention, LeBail
fitting was performed for all peaks in Experimental

Example 2-1 using GSAS (A.C. Larson and R.B. Von Dreele,
"General Structure Analysis System," Report no. LAUR086-
748, Los Alamos National Laboratory, Los Alamos, NM
87545) program, thereby obtaining structure factors.
Then, a crystal structure analysis was performed using a
single crystal structure solution based on CRYSTALS
(D.J. Watkin, C.K. Prout, J.R. Carruthers, P.W.
Betteridge, CRYSTALS, Issue 10; Chemical Crystallography
Laboratory, University of Oxford: Oxford, U.K. 1996).
The crystallographic data of the structural model is as
shown in Table 4.

2-3. Rietveld simulation
The inventors performed X-ray and neutron Rietveld
simulations using the XRDP of the barium/tungsten-
containing oxides of the present invention and the
crystallographic data of the structural model set in
Experimental Example 2.
According to the Rietveld simulations, the
reliability of the structural model was Rw=6% and a
Rietveld profile was fitted over the whole range (see

FIG. 4) . The difference peaks observed below the Bragg
position in the Rietveld profile of FIG. 4 indicate that
the measured peaks conform to the simulation peaks of
the structural model in all measurement sections. This
evidences that the crystal structure determination in
Table 4 using a structural model is correct and that the
metal composite oxides of the present invention (i.e., a
barium/tungsten-containing composite oxides) are all
single phase.
FIG. 5 shows a Fourier synthesis map (atom density
map) of (001) section obtained in a neutron diffraction
analysis. In view of the distribution of 02, 03 and 04
in Table 4, it is determined that W(2) (16c site) forms
a channel in <110> direction and that 02, 03 and 04
around W2 forms an oxygen channel at the same time.
These oxygen atoms are all partially filled due to a low
density. The site occupancies of these oxygen atoms
(i.e., 02, 03 and 04) are much less than 1 as specified
in Table 4.
FIG. 6 is a view showing one layer on ab-cross
section of the barium-tungsten oxide (Ba11W4O23) prepared
in Example 1. In addition to W(1), W(2) and barium,
oxygen atoms are depicted with small circles. W(1)
octahedrons are spaced with a barium atom positioned
between every two adjacent ones. However, in the
arrangement of W(2) polyhedrons, a defect of barium atom
which is indicated by Vu or Vd at 8a site (1/8, 1/8, 1/8)
is observed between every two adjacent. W(2) polyhedrons.
Particularly, defects indicated by Vu or Vd at 8a site
are ordered at intervals on a channel of W2 oxygen
polyhedrons. If the 8a site is occupied by a metal, it
would be difficult to form a channel of W2 oxygen
polyhedrons because of the narrowness of space. In view

of this, the ordering of metal defects appears to be the
most important factor of forming an oxygen channel for
easy movement of oxygen.
2-4. Measurement of distance between oxygen atoms in
crystal
To prove that the ordering of metal defects is
important to form an oxygen channel, the distance
between oxygen atoms in a unit cell was measured.
The measurement was done based on the data in
Table 4 using a generally used crystallographic
calculation program or a structure simulation program
(for example, ATOMS for windows, Ver. 5, 1999, Shape
Software, 521 Hidden Valley Road, Kingsport, TN 37663
USA) .
According to the results of measurement, the
distance between the oxygen atoms 02, 03 and 04 in the
barium-tungsten oxide in Example 1 is less than 2.2Å.
Generally, oxygen atoms cannot be spaced at such a
shorter distance. The measured distance can be an
evidence supporting the fact that the oxygen atoms
present in the metal composite oxides of the present
invention, for example, in a barium-tungsten oxide, are
partially filled, which conforms to the data in Table 4.
2-5. Results of analysis of crystallographic structure
of metal composite oxides
As explained above, the metal composite oxides of
the present invention (i.e., barium/tungsten-containing
composite oxides) have a cubic structure with a unit
cell parameter of 17.0 ±1.0Å and a space group Fd-3m
(no. 227), which is novel and distinguishing from
previously known structures. It was also shown that the

atomic positions in the unit cell of the metal composite
oxides according to the present invention are agree with
those specified in Table 4.
FIG. 7 is a view showing a structural model of the
barium-tungsten oxide (Ba11W4O23) prepared in Example 1.
W(1) octahedrons, 18-coordinated W(2) polyhedrons and
gray barium circles are illustrated. It can be observed
that the W(2) polyhedrons form a channel.
In view of the results of analysis, it is
concluded that the metal composite oxides of the present
invention have a crystal structure with 8b, 48f and 32e
sites occupied by barium, 16d site occupied by W(1), 8a
site with metal defects ordered along the W(2) channel
at 16c site and a channel of W(2) oxygen polyhedrons
formed along the metal defects. It is predictable that
the metal composite oxides of the present invention can
easily conduct oxygen ions due to the oxygen channel
formed along the metal defects.
Experimental Example 2 : Evaluation of oxygen ion
conductivity
The following experiment was carried out to
evaluate the ionic conductivity of the metal composite
oxides prepared according to the present invention.
As samples, the barium/tungsten-containing
composite oxides prepared in Examples 1 to 8 were used.
The conductivity of each sample was measured at a
frequency ranging from 0.1 Hz to 32 MHz using a complex
impedance spectroscopy. After heat stabilization, each
sample was measured in moisture-removed air at an
electric potential of about 100 mV for about 1 hour.
It was turned out that all of the metal composite
oxides having the novel crystal structure according to

the present invention exhibit superior oxygen ion
conductivity at various temperatures (see FIGs. 8, 10,
12 and 14) . Therefore, the metal composite oxides of the
present invention can be used as ionic conductors.
While this invention has been described in
connection with what is presently considered to be the
most practical and preferred embodiment, it is to be
understood that the invention is not limited to the
disclosed embodiment and the drawings, but, on the
contrary, it is intended to cover various modifications
and variations within the spirit and scope of the
appended claims.

WE CLAIM:
1. A Metal composite oxide having the new crystal
structure characterized by conditions (a) to (c):
(a) a space group of Fd-3m (no. 227);
(b) a unit cell parameter of 17.0 ±1.0Å; and
(c) crystallographic positions in a unit cell occupied by
cations with site occupancies as specified in Table 1 (The
crystallographic coordinates in the unit cell are based on
space group No. 227, origin choice).
[Table 1]

2. The metal composite oxide as claimed in claim 1,
wherein said new crystal structure satisfies the conditions
(a), to (c) at temperatures above 100°C.
3. The metal composite oxide as claimed in claim 1,
wherein a crystallographic position in a unit cell is occupied
by at least one anion with a site occupancy as specified in
Table 2.
[Table 2]

4. The metal composite oxide as claimed in claim 1,
wherein a cation occupancy at 8a site (1/8, 1/8, 1/8) in the
unit cell is from 0 to 1.

5. The metal composite oxide as claimed in claim 4,
wherein an atom occupancy at 8a site (1/8, 1/8, 1/8) in the
unit cell is 0.
6. The metal composite oxide as claimed in claim 1,
wherein the oxide is represented by formula (I), (II), (III)
or (IV):

wherein,
A is at least one divalent element selected from the
group consisting of an alkaline earth metal, Cd, Sn, Pb, Sm,
Eu. Er, Tm and Yb;
A' is at least one element selected from the group
consisting of a monovalent alkali metal; a trivalent rare
earth element, Bi(III), Sb(III) or As(III); a tetravalent rare
earth element of Ce(IV), Pr(IV) Tb(IV), Th(IV) or U(IV); and a
cationic element of Zr(IV), Hf(IV) or IIIB through VIA groups;
B is at least one hexavalent element selected from the
group consisting of VIA, VIIA, VIII and VIB, excluding oxygen;
B' is at least one element selected from the group
consisting of Li, Na, Mg, Ca, Sc, Y, rare earth elements
(elements No. 63 to 71) and elements of IIIB to VA groups and
having hexavalent or lower oxidation states;
C is at least one anion or H+ cation selected from the
group consisting of S, F and Cl; and
X is a decimal between 0 and 11 (0≤x≤11), y is a decimal
between 0 and 4 (0≤y≤4) , z is a decimal between 0 and 8
(0≤z≤8), and 8 is a decimal between 0 and 6 (0≤δ≤6).
7. The metal composite oxide as claimed in claim 6,
wherein A in formulae 1 to 4 is a combination of at least one
element selected from the alkaline earth metal group.
8. The metal composite oxide as claimed in claim 7,

wherein A in formulae (I) to (IV) is a combination of Ba and
Sr or Ba and Ca.
9. The metal composite oxide as claimed in claim 6,
wherein A' in formulae (II) to (IV) includes at least one of a
monovalent element or a trivalent element.
10. The metal composite oxide as claimed in claim 9,
wherein said trivalent element is at least one rare earth
element selected from the group consisting of La, Ce, Pr, Nd,
Sm, Eu and Gd.
11. The metal composite oxide as claimed in claim 9,
wherein said monovalent element is K and said trivalent
element is at least one of La, Gd and Bi.
12. The metal composite oxide as claimed in claim 6,
wherein B in formulae (I) to (IV) is at least one element
selected from the group consisting of W, Mo and Cr.
13. The metal composite oxide as claimed in claim 6,
wherein B' in formulae (III) to (IV) is at least one element
selected from the group consisting of Nb, Ta, V and S.
14. The metal composite oxide as claimed in claim 6,
wherein C in formulae 1 to 4 is an H+ cation (proton).
15. The metal composite oxide as claimed in claim 6,
wherein the oxide is Ba11W4O23, Ba10.5Sr0.5W4O23, Ba10Sr1W4O23,
Ba10.5La0.5W4O23.25, Ba10La1W4O23.5, Ba11W3.5Ta0.5O22.75, Ba11W3Ta1O22.5 or
Ba10.5Sr0.5W3.5Ta3.5O22.75.
16. An Ionic conductor comprising metal composite oxides
as defined in any one of Claims 1 to 15.
17. The ionic conductor as claimed in claim 16, wherein
said conductor is oxygen- or proton (H+)-selective.

18. An Electrochemical device comprising the metal
composite oxide as defined in any one of Claims 1 to 15 as an
ionic conductor.
19. The electrochemical device as claimed in claim 18,
wherein said devices are an oxygen probe, a fuel cell, a
chemical membrane reactor, an oxygen separation membrane, an
oxygen pump, a hydrogen separation membrane, a hydrogen pump,
a hydrogen gas sensor, a steam sensor, a hydrocarbon sensor, a
hydrogen extraction, a hydrogen pressure controller, isotope
enrichment, tritium technology, steam electrolysis, H2S
electrolysis, HCl electrolysis, hydrogenation of hydrocarbon,
dehydrogenation, NH3 formation, an electrochemical cell, an
electrochromic device, a gas sensor and a NOX trap.
20. An ionic conductor comprising the metal composite
oxide as defined in claim 1, the ionic conductor forming an
ion channel by the ordering of metal defects in a unit cell.

The invention discloses a metal composite oxide having the new
crystal structure characterized by conditions (a) to (c) : (a)
a space group of Fd-3m (no. 227); (b) a unit cell parameter of
17.0 ±1.0Å; and (c) crystallographic positions in a unit cell
occupied by cations with site occupancies as specified in
Table 1 (The crystallographic coordinates in the unit cell are
based on space group No. 227, origin choice.
[Table 1]

Coordinates of cations (X,Y,Z) Occupancy (0)
8b (3/8, 3/8, 3/8) 0 < 0 ≤ 1
48f (x, 1/8, 1/8), 0.37 ≤ x ≤ 0.43 0 < 0 ≤ 1
32e(x, x, x), 0.20 ≤ x ≤ 0.26 0 < 0 ≤ 1
16d(1/2, 1/2, 1/2) 0 < 0 ≤ 1
16c(0, 0, 0) 0 < 0 ≤ 1