Production Of Barium Titanate Compounds
First Claim
1. A method of producing a powder of barium titanate BaTiO3 including solid solutions and doped compounds thereof, which powder is composed of non agglomerated ultrafine particles of tetragonal barium titanate of high density corresponding to at least 90% of the intrinsic density of a large crystal of the corresponding compound, whose individual particles have an isotropic shape of given aspect ratio all particles being smaller than 1 micron and having a particle size distribution width measured by sedimentation* having a span (dv90−
- dv10)/dv50 less than 1, where dv90 refers to a value such that 90% of the powder volume is made of smaller sizes, dv10 refers to a value such that 10% of the powder volume is made of smaller sizes, and dv50 refers to the volume median diameter such that 50% of the powder volume is made of smaller sizes, and wherein the ratio of Ba;
Ti including their substitutents and dopants is very close to ideal stoichiometry, the method comprising;
*All measurements of particle size distributions by sedimentation in the description and claims are made using a BI-XDCP Particle Sizer instrument. (a) carrying out a first stage reaction between reactants composed of compounds of barium and titanium and optional selected substitutents and dopants by preparing at room temperature a liquid-containing reaction mixture and subjecting the reaction mixture to reaction temperatures in the range 80°
C., preferably 85°
C., to boiling temperature, at a pressure of 1 bar, for a reaction period up to 20 minutes to produce a powder of barium titanate composed of non-agglomerated ultrafine particles having a shape of said given aspect ratio and cubic structure, of low density corresponding at most to 90% of said intrinsic density, all particles being smaller than 1 micron and having a particle size distribution span (dv90−
dv10)/dv50 less than 1, and wherein the ratio of Ba;
Ti including their substitutents and dopants is very close to ideal stoichiometry; and
(b) subjecting the powder of cubic structure produced in step (a) to a second stage solvothermal post treatment at a temperature less than 400°
C. to convert the particles of low density to ultrafine particles of increased density corresponding to at least 90% of said intrinsic density, and converting the isotropic, cubic-structure particles to tetragonal barium titanate particles while maintaining said given aspect ratio and maintaining the size of all particles below 1 micron, the particle size distribution span (dv90−
dv10)/dv50 below 1, and the ratio of Ba;
Ti including their substitutents and dopants very close to ideal stoichiometry.
0 Assignments
0 Petitions
Accused Products
Abstract
An ultrafine powder of barium titanate including solid solutions and doped compounds that meets up to specific characteristics is produced by method comprising two main steps. The first step is a reaction, typically in a Segmented Flow Tubular Reactor, between reactants to produce cubic-structure barium titanate composed of non-agglomerated ultrafine particles having a shape of given aspect ratio, usually a generally spherical shape, of low density corresponding at most to 90% of the intrinsic density, all particles being smaller than 1 micron and having a narrow particle size distribution and wherein the ratio of Ba:Ti including substitutents and dopants is very close to the ideal stoichiometry. This is followed by subjecting the powder produced in the first step to a second stage solvothermal post treatment typically in an autoclave at temperature less than 400° C. to convert the cubic-structure particles of low density to ultrafine tetragonal particles of increased density corresponding to at least 90% of the intrinsic density while maintaining the same aspect ratio, and maintaining the size of all particles below 1 micron, the narrow particle size distribution span, and the given ideal stoichiometry. The produced particles can have a non-spherical facetted shape such as cube-like.
-
Citations
33 Claims
-
1. A method of producing a powder of barium titanate BaTiO3 including solid solutions and doped compounds thereof, which powder is composed of non agglomerated ultrafine particles of tetragonal barium titanate of high density corresponding to at least 90% of the intrinsic density of a large crystal of the corresponding compound, whose individual particles have an isotropic shape of given aspect ratio all particles being smaller than 1 micron and having a particle size distribution width measured by sedimentation* having a span (dv90−
- dv10)/dv50 less than 1, where dv90 refers to a value such that 90% of the powder volume is made of smaller sizes, dv10 refers to a value such that 10% of the powder volume is made of smaller sizes, and dv50 refers to the volume median diameter such that 50% of the powder volume is made of smaller sizes, and wherein the ratio of Ba;
Ti including their substitutents and dopants is very close to ideal stoichiometry, the method comprising;
*All measurements of particle size distributions by sedimentation in the description and claims are made using a BI-XDCP Particle Sizer instrument. (a) carrying out a first stage reaction between reactants composed of compounds of barium and titanium and optional selected substitutents and dopants by preparing at room temperature a liquid-containing reaction mixture and subjecting the reaction mixture to reaction temperatures in the range 80°
C., preferably 85°
C., to boiling temperature, at a pressure of 1 bar, for a reaction period up to 20 minutes to produce a powder of barium titanate composed of non-agglomerated ultrafine particles having a shape of said given aspect ratio and cubic structure, of low density corresponding at most to 90% of said intrinsic density, all particles being smaller than 1 micron and having a particle size distribution span (dv90−
dv10)/dv50 less than 1, and wherein the ratio of Ba;
Ti including their substitutents and dopants is very close to ideal stoichiometry; and
(b) subjecting the powder of cubic structure produced in step (a) to a second stage solvothermal post treatment at a temperature less than 400°
C. to convert the particles of low density to ultrafine particles of increased density corresponding to at least 90% of said intrinsic density, and converting the isotropic, cubic-structure particles to tetragonal barium titanate particles while maintaining said given aspect ratio and maintaining the size of all particles below 1 micron, the particle size distribution span (dv90−
dv10)/dv50 below 1, and the ratio of Ba;
Ti including their substitutents and dopants very close to ideal stoichiometry.- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 33)
- dv10)/dv50 less than 1, where dv90 refers to a value such that 90% of the powder volume is made of smaller sizes, dv10 refers to a value such that 10% of the powder volume is made of smaller sizes, and dv50 refers to the volume median diameter such that 50% of the powder volume is made of smaller sizes, and wherein the ratio of Ba;
-
32. The method of claim 34 wherein the barium titanate powder is formed as a non-supported film.
Specification