Morphologies and crystal structures of nano-sized Ba1−xSrxTiO3 primary particles prepared by flame spray pyrolysis

Nano-sized Ba1−xSrxTiO3 (BST) powder was prepared by flame spray pyrolysis using “CA-assisted” spray solution. The effects of the mole ratios of Ba to Sr components on the mean sizes, morphologies, and crystal structures of the BST powder prepared by flame spray pyrolysis were investigated. The precursor powders obtained by flame spray pyrolysis had large size, fractured and hollow structures irrespective of the mole ratios of Ba to Sr components. The post-treated BST powders had slightly aggregated morphology of the primary particles with nanometer sizes. The slightly aggregated BST powders turned to nano-sized primary particles by a simple milling process. The milled BaTiO3 particles post-treated at temperature of 1000 °C had spherical-like shape. On the other hand, the milled Ba0.5Sr0.5TiO3 and SrTiO3 particles had square shape. The mean sizes of the milled BaTiO3, Ba0.5Sr0.5TiO3 and SrTiO3 particles were each 110, 32, and 48 nm. Phase pure BST powder was obtained at a post-treatment temperature of 1000 °C irrespective of the mole ratios of Ba to Sr components. The BaTiO3 powder had tetragonal crystal structure. On the other hand, the BST except for the BaTiO3 composition had cubic crystal structures at post-treatment temperature of 1000 °C. The mean crystallite sizes of the milled Ba1−xSrxTiO3 primary particles were changed from 29 to 37 nm according to the mole ratios of Ba to Sr components.