Synthesis, characterization and dielectric properties of nanometersized barium strontium titanates prepared by the polymeric citrate precursor method

Barium strontium titanate (BST) powders of the formula Ba1-xSrxTiO3(0less than or equal toxless than or equal to1) have been prepared for the first time by the polymeric precursor route using citric acid and ethylene glycol. Pure BSTs were obtained at 500degreesC. These oxides were found to have the cubic structure, which is retained even after heating at 800degreesC. Detailed X-ray studies on samples sintered at 1100degreesC show weak tetragonal distortion for BaTiO3, while the other BSTs retain their cubic structure. The particle size of the sintered oxides increases from 55 nm for BaTiO3 to 88 nm for SrTiO3, from X-ray line-broadening studies. The nano-sized grains are reasonably stable to sintering (the particle size for BaTiO3 changes from 25 nm at 500degreesC to 55 nm at 1100degreesC). The dielectric constant of the sintered oxides decreases from 510 for BaTiO3 (x=0) to 190 for SrTiO3 (x=1) at 100 kHz. The dielectric loss decreases from 0.05 for BaTiO3 to 0.001 for SrTiO3 at 100 kHz. No ferroelectric transition was observed in either the dielectric studies or by differential scanning calorimetry.