Simple chemical route for the quantitative precipitation of barium-strontium titanyl oxalate precursor leading to Ba1-xSrxTiO3 powders

Barium-strontium titanyl oxalate (BSTO) [Ba1-xSrxTiO(C2O4)(2).4H(2)O with x=0.25 precursor powders] were prepared successfully by using the simple chemical exchange reaction between oxalotitanic acid (HTO) [H2TiO(C2O4)(2).2H(2)O], barium hydroxide and strontium nitrate at room temperature. Initially, oxalotitanic acid was prepared by using the reaction between 0.1 M titanium tetrabutoxide and 0.2 M oxalic acid in isopropano (IPA). Barium hydroxide and strontium nitrate were added directly to this solution in stoichiometric amounts. The required solubility achieved only after addition of distilled water dropwise leads to the controlled precipitation of BSTO molecular precursor. To maintain the equilibrium (pH conditions), more and more Ba(OH)(2) and Sr(NO3)(2) solids get dissolved and reaction continues. The kinetics of exchange reaction is governed by the rate of addition of water. The pyrolysis of BSTO at 750 degreesC/4 h in air produced the Ba1-xSrxTiO3 (BST) powders. The characterization studies were carried on the as-dried and calcined powders by various physicochemical techniques viz. microanalysis, chemical analysis, DTA/TGA, XRD, IR, scanning electron microscopy (SEM), etc. It revealed that the BST powders are cubic, stoichiometric, highly pure with yield>99% and agglomerated nature (size: 0.5-2 mum). (C) 2002 Elsevier Science B.V. All rights reserved.