Method of preparing ceramic powders using ammonium oxalate

Abstract

Wet-chemical methods involving the use of water-soluble hydrolytically stable metal-ion chelate precursors and an ammonium oxalate precipitant can be used in a coprecipitation procedure for the preparation of ceramic powders. Both the precursor solution and the ammonium oxalate precipitant solution are at neutral or near-neutral pH. 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 ceramic powder comprising:
 providing precursor materials in a precursor solution, wherein each of the precursor materials in the precursor solution further comprises a constituent species of the ceramic powder;   combining the precursor solution and an ammonium oxalate precipitant solution to co-precipitate the ceramic powder within a resulting slurry;   transferring the resulting slurry to a filtration or separating device; and   separating the ceramic powder from the resulting slurry.   
     
     
         2 . The method of  claim 1 , further comprising preparing the precursor solution using a first precursor material and a second precursor material, wherein the first precursor material includes a metal nitrate, and the second precursor material includes a chelate solution. 
     
     
         3 . The method of  claim 2 , wherein the chelate solution comprises a first metal chelate. 
     
     
         4 . The method of  claim 2 , wherein a first metal within the first metal chelate comprises Ti, Zr, Mn, Ga, Ag, Nb, Mo, Y, La, Pr, Nd, Sm, Gd, Dy, Er, Ho, Yb or any combination thereof. 
     
     
         5 . The method of  claim 2 , wherein the first metal chelate comprises a titanium(IV) bis(ammonium 2-hydroxypropanato)dihydroxide. 
     
     
         6 . The method of  claim 2 , wherein the chelate solution further comprises a second metal chelate. 
     
     
         7 . The method of  claim 6 , wherein the second metal chelate comprises:
 a zirconium(IV) bis(ammonium 2-hydroxypropanato)dihydroxide;   a bis(ammonium 2-hydroxypropanato)manganese(II);   a tris(ammonium 2-hydroxypropanato)yttrium(III);   a tris(ammonium 2-hydroxypropanato)lanthanum(III); or   a tris(ammonium 2-hydroxypropanato)neodymium(III).   
     
     
         8 . The method of  claim 6 , wherein the first precursor material comprises Ba(NO 3 ) 2 , Ca(NO 3 ) 2 .4H 2 O, Nd(NO 3 ) 3 .6H 2 O, Y(NO 3 ) 3 .4H 2 O, ZrO(NO 3 ), or any combination thereof. 
     
     
         9 . The method of  claim 2 , wherein the first precursor material comprises Ba(NO 3 ) 2 , Ca(NO 3 ) 2 .4H 2 O, Nd(NO 3 ) 3 .6H 2 O, Y(NO 3 ) 3 .4H 2 O, ZrO(NO 3 ), or any combination thereof. 
     
     
         10 . The method of  claim 1 , wherein separating comprises:
 filtering the ceramic powder from the combined solution;   centrifuging the combined solution;   sedimenting the combined solution;   spray drying the combined solution;   freeze drying the combined solution; or   any combination thereof.   
     
     
         11 . The method of  claim 1 , further comprising, after separating the ceramic powder from the resulting slurry:
 washing the ceramic powder;   drying the ceramic powder;   calcining the ceramic powder;   sintering the ceramic powder or   any combination thereof.   
     
     
         12 . The method of  claim 1 , wherein the ceramic powder is a composition-modified barium titanate powder. 
     
     
         13 . A method of forming a ceramic powder comprising:
 providing precursor materials in a precursor solution, wherein each of the precursor materials in the precursor solution further comprises a constituent species of the ceramic powder;   combining the precursor solution and an ammonium oxalate precipitant solution to co-precipitate the ceramic powder within a resulting slurry, wherein the resulting slurry is substantially free of any alkali metals; and   separating the ceramic powder from the resulting slurry.   
     
     
         14 . The method of  claim 13 , further comprising preparing a chelate solution as a particular precursor solution. 
     
     
         15 . The method of  claim 14 , wherein the chelate solution further comprises a chelate agent and a tetraalkyl ammonium hydroxide. 
     
     
         16 . The method of  claim 15 , wherein the chelate agent comprises an alpha-hydroxycarboxylic acid. 
     
     
         17 . The method of  claim 15 , wherein preparing a chelate solution comprises combining a metal carbonate, the chelate agent, and the tetraalkyl ammonium hydroxide. 
     
     
         18 . The method of  claim 15 , wherein the preparing the chelating solution is performed at a pH of approximately 6 to approximately 8. 
     
     
         19 . The method of  claim 13 , wherein the ceramic powder is a composition-modified barium titanate powder. 
     
     
         20 . A method of forming a ceramic powder comprising:
 providing precursor materials in a precursor solution, wherein each of the precursor materials in the precursor solution further comprises a constituent species of the ceramic powder;   combining the precursor solution and an ammonium oxalate precipitant solution to co-precipitate the ceramic powder within a resulting slurry having a pH in a range of approximately 6 to approximately 8; and   separating the ceramic powder from the resulting slurry.