Field of invention:
The present invention relates to a method of manufacturing nano sized alkaline
earth metal titanate powder and more particularly is directed to a method of
manufacturing nano sized barium titanate, strontium titanate and calcium titanate
powder.
Background and prior art:
Alkaline earth metal powders have been prepared by different synthetic routes,
some of which are:
1) high temperature solid state synthesis, using metal oxides or carbonates
2) chemical synthesis: This method is further sub-divided into the following
classes:
(i) hydro-thermal method
(ii) combustion method
(iii) precipitation method
(iv) solid state reaction method
(v) sol gel method
With the advancement in technology, the requirements of purity, phase
distribution, and other physical characteristics of ceramic powders have become
more stringent and thus, chemical synthesis methods are gaining importance.
Chemically prepared powders are pure and homogenous at a molecular level.
Their chemical and physical characteristics can be more closely monitored and
controlled by modulating the reaction conditions and parameters. The chemical
processes can also be carried out at significantly lower temperatures than the
conventional methods. In addition, the grinding and refining steps can also be
eliminated using the chemical processes of synthesis. All these advantages
result in substantial cost savings associated with using the chemical methods of
synthesis.
Following the general principles enshrined in the prior art, most of the processes
already known used common precursor solutions like titanium oxychloride,
2

titanium oxynitrate, titanium oxysulphate and titanium alkoxides. Titanium
alkoxide as precursor compound is very expensive and thus it makes the whole
process uneconomic. None of the methods known in the prior art used naturally
occurring ilmenite ore as the precursor to the synthesis of nano-sized alkaline
earth titanates.
The chemical methods known in the prior art also have certain deficiencies
associated with them. Hydrothermal method of synthesis is a very time
consuming process and is not commercially applicable. Combustion method of
synthesis involves the preparation of precursor solutions of metal ions with the
help of chelating agent(s) and polymers to form a polymer matrix which are
costly. Combustion methods can produce chemically homogenous compounds in
the nano-size range, but they too require selective ingredients to fulfill the
reaction conditions, which makes the process costlier.
Thus, there is a long felt need for an improved process for the preparation of
alkaline earth metal titanates which is conspicuously devoid of those
disadvantages and drawbacks to date characterizing the state of this art, and
which improved process enables preparation of such nano-sized alkaline earth
metal titanates both reliably and reproducibly, and directly in the form of powders
which are homogeneous both as to morphology and composition.
Objects of the invention
It is an object of the present invention to provide an improved method of
manufacturing alkaline earth metal titanate powder.
It is another object of the present invention to provide a method of manufacturing
nano sized alkaline earth metal titanate powder having a narrow particle size
distribution.
3

It is a further object of the present invention to provide a method of
manufacturing nano sized alkaline earth metal titanate powder using a simple,
efficient, economical and convenient process.
Yet another object of the present invention is the provision of a method which
enables preparation of alkaline earth metal titanates both reliably and
reproducibly and directly in the form of nano sized powders which are
homogenous both as to morphology and composition.
The other objects, features and advantages of the present invention will become
apparent from the following description taken in conjunction with the examples.
To overcome the drawbacks of prior art and to fulfill the long felt need the present
inventors have devised a new methodology for the synthesis of titanates to be
used as pigment. The method is based on:
(i) use of cheap ingredients for the extraction of titanium as water soluble
oxychlorides from naturally available ilmenite ore, and
(ii) the synthesis of nano-sized alkaline earth metal titanates in large scale
for industrial application using cheap reagents.
Summary of the invention
Thus the present invention relates to a process which comprises fusing the
ilmenite ore using sodium hydroxide/ sodium carbonate, separating the iron
content to minimal quantity, preparing a solution of titanium oxychloride and
thereafter precipitating the precursor of nano-sized alkaline earth metal titanates
from the solution mixture of alkaline earth metal chloride and titanium oxychloride
using ammonium carbonate or sodium carbonate and there after calcining to
get nano-sized titanates of alkaline earth metals.
According to one embodiment of the invention there is provided a process for the
cost-effective preparation of alkaline earth metal titanate pigments, said process
comprising:
4

(a) extraction of titanium as its water soluble oxychloride salt from the ilmenite
ore;
(b) selective separation of iron content from the solution,
(c) production of precursor fine powders of alkaline earth metal titanates
using precipitating agents on the mixture comprising alkaline earth metal
chlorides and titanium oxychloride, and
(d) calcining the white precipitated mass to nanosized titanates.
According to another embodiment there is provided a process for the cost-
effective preparation of nano-sized barium titanate or strontium titanate or
calcium titanate powder, said process comprising:
(a) extraction of titanium as its water soluble oxychloride salt from the ilmenite
ore;
(b) selective separation of iron content from the solution;
(c) production of precursors of nano-sized powders of barium titanate or
strontium titanate or calcium titanate powder by using precipitating agents
on the mixture comprising barium chloride (BaCI2.2H2O) or strontium
chloride (SrCI2.6H2O) or calcium chloride(CaCI2.2H2O) and titanium
oxychloride;
(d) calcining the white precipitated mass thus obtained to get nano-sized
titanates.
Detailed description of the invention
The extraction of titanium as its oxysulphate from naturally available ilmenite ore
using the well-known sulfuric acid digestion method is not a simple one. It suffers
from some technical difficulties. The present inventors have devised a rather
easy process for the extraction of titanium as water soluble oxychloride salt. The
process according to the present invention comprises:
1) fusing the ore with sodium hydroxide/ sodium carbonate for six hours and
dissolution of solid mass in water to remove alkalies;
5

2) a simple separation method for leaching the iron content selectively from solid
mass by requisite amount of HCI;
3) The solid mass mostly Ti oxide-hydroxide is dissolved in HCI and residual Fe3+
is removed by solvent extraction using Tributyl phosphate or its mixture with
organic solvent.
The excess or unreacted sodium hydroxide/ sodium carbonate is recovered and
reused. The titanium oxychloride salt, thus obtained is substantially free of any
iron content.
The precursor of alkaline earth metal titanates is precipitated from the solution
mixture of alkaline earth metal chloride and titanium oxychloride using
ammonium carbonate or sodium carbonate as the precipitating agent. This
precursors on calcinations produce fine powders of alkaline earth metal titanates
with nanosized particles in high volume, good quality and low cost.
Controlling the pH of the medium for the synthesis of nanosized alkaline earth
metal titanates is an important parameter. For different titanates different pH is
maintained varying from neutral to strongly alkaline solutions. The particular pH
used will be varied depending upon the initial metal ions present in the system its
tendency to be precipitated from the solution mixture. For the synthesis of
CaTiO3, a lower pH in the neutral range is required, more preferably a pH ranging
from pH 7-8 is maintained. A pH of around 10 is adjusted for SrTiO3 and BaTiO3,
more preferably in the range of pH 10-12. Control of pH is accomplished by the
addition of ammonium carbonate/ sodium carbonate in required amounts.
The conditions of pH, temperature, reactant concentration, rate of addition of
reactants to the precipitants, calcination temperature etc. are adjusted for a
particular reaction.
The calcination of the white precipitated mass is also an important step in the
present invention. This step signifies the duration of calcination as well as the
temperature at which the precipitated mass is calcined. The precipitated mass
6

according to the present invention is calcined at 800°C for 3 hours. The calcined
mass is soft, porous and easy to grind.
Preferred calcination temperatures will be at least about 700°C, and usually in
the range of about 600°C to 1000°C. It should be understood however, that the
particular calcination temperature used may vary depending upon the starting
materials used and the properties of the desired product. In this regard, for
example, inventive products can be provided in the form of amorphous powders,
which may generally be formed at relatively lower temperatures, or crystalline
powders, which may be formed at relatively higher temperatures. For the
crystallization of the powder, the minimum temperature of 800°C is required.
For obtaining the better quality of pigment, the titanium oxychloride solution
should have the iron content as minimum as possible. The presence of a
transition metal ion e.g. iron, harms the efficiency of white colour of the pigment.
Hence, the removal of iron content from the bulk solution of titanium oxychloride
is preferably achieved to the ppm level.
The details of the invention, its objects and advantages are explained hereunder
in greater detail in relation to non-limiting exemplary illustrations. The examples
are merely illustrative and do not limit the teaching of this invention and it would
be obvious that various modifications or changes in the procedural steps by
those skilled in the art without departing from the scope of the invention and shall
be consequently encompassed with in the ambit and spirit of this approach and
scope thereof.
Example 1:
Calcium. Barium and Strontium titanates are prepared by chemical co-
precipitation methods from titanyl chloride solution
7

With respect to TiO2 content in titanyl chloride solution, the chloride of earth
metal were taken in 1:1 mole ratio. In titanyl chloride solution TiO2 content was
measured by taking known amount of titanyl solution, precipitating the titanium
hydroxide with dilute ammonia completely and washing the precipitate with
deionized water to remove CI- ion and then calcining the solid mass at 900°C for
4 hrs. CaCI2.2H2O or SrCI2.6H2O or BaCI2.2H2O are taken as raw materials.
These raw materials are then added to the titanyl chloride solution in mole ratio
1:1. This mixture solution is then added drop wise into an aqueous solution of
ammonium carbonate ( 15% (Wt/ Volume) 120 ml) under vigorous stirring
conditions by use of a mechanical stirrer. The pH of the solution is maintained at
7-10(checking the pH by pH meter). The reaction is carried out at room
temperature. The white precipitate is then repeatedly washed with 20 ml of water
followed by filtration. . Preferably, the white precipitate is washed seven times
with deionized water to remove the chloride ions ( complete removal of
choloride ion can be checked by taking the drop of filtrate in AgNO3 solution,
presence of chloride indicated by white precipitation of AgCI) . The white mass is
then dried in an oven and calcined at 800°C for 3 hours.
For the extraction of titanium as its oxychloride, the ilmenite ore is fused with
sodium hydroxide/ sodium carbonate ( ilmenite ore to sodium hydroxide mole
ratio is 1: 4-7. The ore and sodium hydroxide/ sodium carbonate are mixed in a
ratio of 1:7, and more preferably 1:4). The mixture is fused in the steel crucible at
700°C to 1200°C for 6 hours. The resulting red or reddish fused mass is leached
with water to remove alkalies and then with dilute 10 ml 3 (N) HCI to 1 gm of
fused mass, just in an amount sufficient to completely react with hydrated oxide
of iron present in leached mass. The white solid mass is then separated by
filtration and is dissolved in 10 ml conc.HCI (12 N ) for 1gm of fused mass . This
solution is then subjected to solvent extraction after diluting with water ( 2-6 times
by volume )using kerosene and Tri n-butyl phosphate and thiocyanate of
ammonium (very little amount)/sodium/potassium as an additive for the selective
separation of residual iron from the resulting solution.
8

"Particle size" is defined as the mean diameter of particles. The synthesized
product ( precursor of alkaline earth metal titanate ) has a surface area of 216
m2/g having an average particle size less than 100 nano-meter as determined by
BET surface area measurements The nanosized, non-agglomerated precursors
of alkaline earth metal titanate particles, so obtained, are in the aqueous phase.
The material so obtained retains the surface area defined above even when
stored at the room temperature for several months. The material even maintains
the above-noted surface areas when heated to 800°C for 6-8 hours even after
the formation of nano-sized alkaline earth metal titanates.
Brief description of figures
Reference is now drawn to figure 1, which shows the X-ray diffraction pattern of
the synthesized particles.
Figure 2 shows the BET isotherm of the synthesized particles.
Figure 3 shows the BET or Langmuir function vs. the relative pressure.
9

We claim:
1. A process for the cost-effective preparation of alkaline earth metal titanate
pigments, said process comprising:
a) extraction of titanium as its water soluble oxychloride salt from the ilmenite
ore;
b) selective separation of iron content from the solution;
c) production of precursors precipitate for fine powders of alkaline earth
metal titanates using precipitating agents on the mixture comprising
alkaline earth metal chlorides and titanium oxychloride, and
d) calcining the white precipitated precursor mass.to get fine powders of
alkaline earth metal titanates
2. A process for the cost-effective preparation of nano-sized Barium titanate or
Strontium titanate or Calcium titanate powder, said process comprising:
a) extraction of titanium as its water soluble oxychloride salt from the ilmenite
ore;
b) selective separation of iron content from the solution, and
c) production of white precipitate of precursor materials for nano-sized
powders of Barium titanate or Strontium titanate or Calcium titanate
powder by using precipitating agents on the mixture comprising Barium
chloride (BaCI2.2H2O) or Strontium chloride (SrCI2.6H2O) or Clacium
chloride(CaCI2.2H2O) and Titanium oxychloride.
d) calcining the white precipitated precursor material mass thus obtained to
get nano-sized alkaline metal titanates
3. A process as claimed in claims 1 or 2, wherein the said step (a) for extracting
titanium as its water soluble oxychloride, comprises:
(a) fusing the ilmenite ore using a base for 6 hours
(b) The fused mass is leached with water to remove alkalies
(c) The residue is treated with requisite amount of HCI just to dissolve
hydrated iron ( 3+ ) oxide mostly.
10

(d) The residue after removal of major amount of iron oxide is dissolved in
HCI to form titanium oxy chloride
(e) The residual Fe3+ is removed from titaniumoxy chloride solution by
solvent extraction using Butyl phosphate and inorganic thicuanate
(f) dissolution of the solid mass in HCI.
11
4. A process as claimed in claim 3, wherein the base used for extraction of
titanium as its water-soluble oxychloride, is selected from sodium hydroxide
or sodium carbonate.
5. A process as claimed in claim 1 or 2, wherein in the step (c) of precipitation of
precursor material for CaTiO3,a pH of 7 - 8 is maintained.
6. A process as claimed in claim 1 or 2, wherein in the step (c) of precipitation of
precursor material for SrTiO3, pH of 8 - 10 is maintained.
7. A process as claimed in claim 1 or 2, wherein in the step (c) of precipitation of
precursor material for BaTiO3, a pH of 10 - 12 is maintained.
8. A process as claimed in claims 1 or 2, wherein the step (d) of calcining of the
white precipitated mass is done at a temperature of 600 - 1000°C.
9. A process as claimed in claim 3, wherein the solvent used for extraction of
Fe3+ from titanium oxychloride is a mixture of kerosene and Tri n-
butylphosphate.
10. A process for the cost-effective preparation of alkaline earth metal titanate
pigments substantially as described herein and illustrated with reference to
the accompanying examples.

Preparation of nanosized alkaline earth metal titan ate (MTiO3) pigments by an
easy and cost effective process with reasonable yield, the said process
comprising extraction of titanium as its water soluble ox chloride salt selective
separation of iron content from the solution, and production of precursor powder
of alkaline earth metal titanates using precipitating agents with the mixture
comprising alkaline earth metal chlorides and titanium oxychioride, and calcining
the while precipitated mass thus obtained to produce fine powders of alkaline
earth metal titanates.