Ferroelectric phase transition in Sn2+ ions doped (Ba,Ca)TiO3 ceramics

Solid solutions of BaTiO3 ferroelectric ceramics containing Sn2+ ions have been synthesized by solid state reaction with Ca2+ codoping. The crystal structures of Sn2+ ions doped (Ba,Ca)TiO3 were identified as tetragonal perovskite type BaTiO3 based on x-ray diffraction profiles analysis. (Ba1-xCax)TiO3 (x=0.13) tetragonality increased with Sn ions doping. Temperature dependence of the dielectric properties for Sn2+ ions doped (Ba1-xCax)TiO3 ceramic sample showed a tetragonal-to-cubic phase transition temperature of 155 degrees C, which is higher than that of undoped (Ba1-xCax)TiO3 (135 degrees C). By using synchrotron x-ray absorption near-edge structure spectroscopy the valence state of Sn ions in the (Ba1-x-yCaxSny)TiO3 (x=0.13, y=0.05) ferroelectric ceramics was identified to be Sn2+.