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 potassiu m titanyl oxalate as starting materials. Precipitate obtained at pH = 5.0 c orresponded to a physical mixture of BiO(HC2O4) and TiO(OH)(2)H2O in the ra tio of 4.3, but on pyrolysis this did not yield phase pure Bi4Ti3O12. Howev er, 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 degre es C yielded phase pure Bi4Ti3O12. (C) 2000 Elsevier Science B.V. All right s reserved.