Bismuth titanate from coprecipitated stoichiometric hydroxide precursors

The effect of pH on the formation of stoichiometric precursors for bismuth titanate was investigated by thermal analysis using Bi(NO3)(3) and potassium titanyl oxalate as starting materials. Precipitate obtained at pH = 5.0 corresponded to a physical mixture of BiO(HC2O4) and TiO(OH)(2)H2O in the ratio of 4.3, but on pyrolysis this did not yield phase pure Bi4Ti3O12. However, at 1 M NH4OH stoichiometric mixture of 4Bi(OH)(3) + 3TiO(OH)(2)H2O was obtained by reverse titration and the precipitate on pyrolysis at 750 degrees C yielded phase pure Bi4Ti3O12. (C) 2000 Elsevier Science B.V. All rights reserved.