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Method of preparing ceramic powders using chelate precursors

  • US 7,914,755 B2
  • Filed: 03/07/2006
  • Issued: 03/29/2011
  • Est. Priority Date: 04/12/2001
  • Status: Active Grant
First Claim
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1. A method of forming a composition-modified barium titanate ceramic powder, with a formula of (Ba1-α





  • Aμ

    Dν

    Caα

    )[Ti1-x-δ









    Mnδ

    A′

    μ



    D′

    ν



    Zrx]zO3, where A=Ag or La, A′

    =Dy, Er, Ho, Y, Yb, or Ga;

    D=Nd, Pr, Sm, or Gd;

    D′

    =Nb or Mo, 0.10≦

    x≦

    0.25;

    0≦

    μ



    0.01, 0≦

    μ





    0.01, 0≦

    ν



    0.01, 0≦

    ν





    0.01, 0≦

    δ



    0.01, 0.995≦

    z≦

    1, and 0≦

    α



    0.005 the method comprising;

    individually forming each of a plurality of water-stable constituent ion chelates, wherein each of the water-stable constituent ion chelates is formed from a constituent ionic species of the ceramic powder, ammonium hydroxide, and a chelate agent, a plurality of water-stable constituent ion chelates including ionic species zirconium, manganese, yttrium, lanthanum, and neodymium, the chelate agent comprising 2-hydroxypropanoic acid or an alpha-hydroxycarboxylic acid selected from the group consisting of 2-hydroxyethanoic acid, 2-hydroxybutanedioic acid, 2,3-dihydroxybutanedioic acid, 2-hydroxy-1,2,3-propanetricarboxylic acid, 2-hydroxybutanoic acid, 2-hydroxypentanoic acid, and 2-hydroxyhexanoic acid;

    providing a plurality of precursor materials in an aqueous solution, a first precursor material of the plurality of precursor materials comprising Ba(NO3)2 and calcium nitrate, a second precursor comprising a stable titanium alpha-carboxylic acid chelate, a third precursor material of the plurality of precursor materials comprising the plurality of water-stable constituent ion chelates;

    combining the plurality of precursor materials in the aqueous solution with a precipitant solution to cause coprecipitation of primary particles of the ceramic powder in a combined solution, the precipitant solution comprising tetraalkylammonium hydroxide, the primary particles comprising the first, second, and third precursors;

    refluxing the coprecipitated primary particles of the ceramic powder;

    separating the ceramic powder from the combined solution; and

    calcining the ceramic powder, the primary particles of the ceramic powder comprising composition-modified barium titanate having a perovskite structure.

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