Simple oxalate precursor route for the preparation of barium-strontium titanate: Ba1−xSrxTiO3 powders

A simple one-step cation-exchange reaction between the stoichiometric solutions of ammonium titanyl oxalate (ATO) and barium hydroxide+strontium nitrate at room temperature (RT) is investigated successfully for the quantitative precipitation of barium-strontium titanyl oxalate (BSTO): Ba1−xSrxTiO(C2O4)2·4H2O (x=0.25) precursor powders with nearly theoretical yield (≥99%). The pyrolysis of BSTO at 730 °C/4 h in air produced barium-strontium titanate (Ba1−xSrxTiO3; BST) powders. The characterization studies on BSTO and BST powders by using various physico-chemical techniques: micro- and chemical analysis, differential thermal analysis (DTA)/thermo-gravimetric analysis (TGA), XRD, FTIR, X-ray fluorescence (XRF) and scanning electron microscopy (SEM) revealed that the powders formed are cubic, highly pure, stoichiometric and sub-micron-sized with nearly uniform size and shape distribution. The ceramic compacts obtained by sintering the BST pellets at 1300 °C/4 h showed density ∼95%, dielectric constant ɛ(Tc)∼9500, tan δ∼0.15% and TC∼32 °C.