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Production Of Barium Titanate Compounds

  • US 20070202036A1
  • Filed: 04/07/2005
  • Published: 08/30/2007
  • Est. Priority Date: 04/07/2004
  • Status: Abandoned Application
First Claim
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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.

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