Stoichiometry control and phase selection in hydrothermally derived BaxSr1-xTiO3 powders

BaxSr1-xTiO3 (BST) powders were processed at temperatures <100 degrees C by reacting nanosized TiO2 powders in alkaline, aqueous solutions of BaCl2, S rCl2, and NaOH. The effects of processing variables (NaOH concentration, ti me, temperature, and the ratios of barium, strontium, and titanium initiall y in solution) on the resultant BST powder stoichiometry and solid solubili ty were examined. In all cases, strontium was more readily incorporated int o the BST powders than barium, and the extent varied systematically with th e processing variables. BST powders that were processed in solutions with a large initial excess of barium and strontium, relative to titanium, consis ted of a single-phase solid solution. In contrast, BST powders that were pr ocessed in solutions with a small initial excess of barium and strontium, r elative to titanium, contained a biphasic solid solution which corresponded to separate barium-rich and strontium-rich phases.