Method of preparing ceramic powders using chelate precursors

Abstract

Wet-chemical methods involving the use of water-soluble hydrolytically stable metal-ion chelate precursors and the use of a nonmetal-ion-containing strong base can be used in a coprecipitation procedure for the preparation of ceramic powders. Examples of the precipitants used include tetraalkylammonium hydroxides. A composition-modified barium titanate is one of the ceramic powders that can be produced. Certain metal-ion chelates can be prepared from 2-hydroxypropanoic acid and ammonium hydroxide.

1 . A method of forming a composition-modified barium titanate ceramic powder, the method comprising:
 forming an aqueous solution from precursor materials comprising barium nitrate, calcium nitrate, a titanium alpha-carboxylic acid chelate, and a plurality of water-stable constituent ion chelates, each water-stable constituent ion chelate of the plurality of water-stable constituent ion chelates including an ionic species and a chelating agent, the ionic species including zirconium, manganese, yttrium, lanthanum, or neodymium, the chelating agent including 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;   combining the plurality of precursor materials in the aqueous solution with a precipitant solution to coprecipitate of primary particles in a combined solution, the precipitant solution comprising tetraalkylammonium hydroxide, the primary particles comprising the barium, calcium, titanium, and each ionic species of the plurality of water stable constituent ion chelates;   refluxing the coprecipitated primary particles;   separating the refluxed primary particles from the combined solution; and   calcining the separated primary particles, the primary particles forming a ceramic powder comprising composition-modified barium titanate having a perovskite structure.   
     
     
         2 . The method of  claim 1 , wherein the ionic species of the plurality of water-stable constituent ion chelates further include Pr, Sm, Gd, Dy, Er, Ho, Yb, Ga, Ag, Dy, Er, Ho, Nb, or Mo. 
     
     
         3 . The method of  claim 1 , wherein the tetraalkylammonium hydroxide is tetramethylammonium hydroxide. 
     
     
         4 . The method of  claim 1 , wherein the separating further comprises at least one of filtering the primary particles from the combined solution; centrifuging the combined solution; sedimenting the combined solution; spray drying the combined solution; or freeze drying the combined solution. 
     
     
         5 . The method of  claim 1 , further comprising at least one of washing the separated primary particles; drying the separated primary particles; or sintering the separated primary particles. 
     
     
         6 . The method of  claim 1 , wherein at least one ionic species is derived from a metal alkyl oxide. 
     
     
         7 . The method of  claim 1 , wherein at least one ionic species is derived from a metal ion carbonate. 
     
     
         8 . The method of  claim 1 , wherein the composition-modified barium titanate is barium-calcium-zirconium-titanate. 
     
     
         9 . The method of  claim 1 , wherein the composition-modified barium titanate is (Ba 1-α-μ-ν A μ D ν Ca α )[Ti 1-x-δ-μ′-ν′ Mn δ A′ μ′ D′ ν′ Zr x ] z O 3 , 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, and 0.995≦z≦0≦α≦0.005. 
     
     
         10 . The method of  claim 1 , wherein refluxing includes refluxing at 90° C. to 95° C. 
     
     
         11 . A method of forming a ceramic powder for use in a dielectric material, the method comprising:
 for each constituent metal species selected from zirconium, manganese, yttrium, lanthanum, or neodymium:
 mixing a solution comprising a constituent metal ion or oxometal ion and a solution comprising an alpha-hydroxycarboxylic acid to form a constituent metal ion chelate or an oxometal ion chelate; and 
 stabilizing the metal ion chelate or the oxometal ion chelate by adding ammonium hydroxide, the stabilized metal ion chelate or the stabilized oxometal ion chelate remaining in solution; 
   forming a solution including barium nitrate, calcium nitrate, a stabilized titanium ion chelate, and each of the stabilized metal ion chelates or the stabilized oxometal ion chelate;   precipitating primary particles by adding to the solution tetraalkylammonium hydroxide, the primary particles comprising barium, calcium, titanium, and the constituent metal species;   refluxing the primary particles; and   calcining the primary particles, the calcined primary particles forming the ceramic powder comprising composition-modified barium titanate having a perovskite structure.   
     
     
         12 . The method of  claim 11 , wherein the tetraalkylammonium hydroxide comprises tetramethylammonium hydroxide. 
     
     
         13 . The method of  claim 11 , further comprising separating the primary particles of the ceramic powder from solution prior to calcining. 
     
     
         14 . The method of  claim 11 , wherein refluxing includes refluxing at 90° C. to 95° C. 
     
     
         15 . The method of  claim 11 , wherein the alpha-hydroxycarboxylic acid is 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. 
     
     
         16 . The method of  claim 15 , wherein the alpha-hydroxycarboxylic acid is 2-hydroxy-1,2,3-propanetricarboxylic acid. 
     
     
         17 . The method of  claim 11 , wherein the alpha-hydroxycarboxylic acid is 2-hydroxypropanoic acid. 
     
     
         18 . The method of  claim 11 , wherein the composition-modified barium titanate is barium-calcium-zirconium-titanate. 
     
     
         19 . The method of  claim 11 , wherein the composition-modified barium titanate is (Ba 1-α-μ-ν A μ D ν Ca α )[Ti 1-x-δ-μ′-ν′ Mn δ A′ μ′ D′ ν′ Zr x ] z O 3 , where A=Ag, A′=Dy, Er, Ho, Y, Yb, or Go; 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, and 0.995≦z≦0≦α≦0.005. 
     
     
         20 . A method of forming a ceramic powder for use in a dielectric material, the method comprising:
 individually forming each of a plurality of stabilized metal ion chelates or stabilized oxometal ion chelates, wherein each of the stabilized metal ion chelates or oxometal ion chelates is formed from a constituent ionic species of a plurality of constituent ionic species, ammonium hydroxide, and a chelate agent, the plurality constituent ionic species including 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;   forming a first solution from barium nitrate, calcium nitrate, a stabilized titanium ion chelate, and the plurality of stabilized metal ion chelates or oxometal ion chelates;   precipitating primary particles including barium, titanium and the plurality of constituent ionic species by adding a second solution comprising tetraalkylammonium hydroxide;   refluxing the primary particles in solution;   separating the primary particles from solution; and   calcining the primary particles, the calcined primary particles forming the ceramic powder comprising composition-modified barium titanate having a perovskite structure.   
     
     
         21 . The method of  claim 20 , wherein the tetraalkylammonium hydroxide comprises tetramethylammonium hydroxide. 
     
     
         22 . The method of  claim 20 , wherein refluxing the precipitated primary particles includes refluxing at 90° C. to 95° C. 
     
     
         23 . The method of  claim 20 , wherein the composition-modified barium titanate is barium-calcium-zirconium-titanate. 
     
     
         24 . The method of  claim 20 , wherein the composition-modified barium titanate is (Ba 1-α-μ-ν A μ D ν Ca α )[Ti 1-x-δ-μ′-ν′ Mn δ A′ μ′ D′ ν′ Zr x ] z O 3 , where A=Ag, 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, and 0.995≦z≦0≦α≦0.005. 
     
     
         25 . A method of forming a ceramic powder for use in a dielectric material, the method comprising:
 forming a first solution from barium nitrate, calcium nitrate, a stabilized titanium ion chelate, and a plurality of stabilized metal ion chelates or oxometal ion chelates, each of the stabilized metal ion chelates or oxometal ion chelates is formed from a constituent ionic species of the ceramic powder, a hydroxide, and a chelate agent, the plurality of water-stable constituent ion chelates including the 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;   precipitating primary particles, the primary particles including barium, titanium and the constituent ionic species by adding a second solution comprising tetraalkylammonium hydroxide;   refluxing the primary particles in solution;   separating the primary particles from solution; and   calcining the primary particles, the calcined primary particles forming the ceramic powder comprising composition-modified barium titanate having a perovskite structure.   
     
     
         26 . The method of  claim 25 , wherein the composition-modified barium titanate is barium-calcium-zirconium-titanate. 
     
     
         27 . The method of  claim 25 , wherein the composition-modified barium titanate is (Ba 1-α-μ-ν A μ D ν Ca α )[Ti 1-x-δ-μ′-ν′ Mn δ A′ μ′ D′ ν′ Zr x ] z O 3 , where A=Ag, A′=Dy, Er, Ho, Y, Yb, or Go; 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, and 0.995≦z≦0≦α≦0.005.