Ferroelectric phase transition in Sn~(2+) ions doped (Ba,Ca)TiO_3 ceramics

摘要

Solid solutions of BaTiO_3 ferroelectric ceramics containing Sn~(2+) ions have been synthesized by solid state reaction with Ca~(2+) codoping. The crystal structures of Sn~(2+) ions doped (Ba,Ca)TiO_3 were identified as tetragonal perovskite type BaTiO_3 based on x-ray diffraction profiles analysis. (Ba_(1-x)Ca_x)TiO_3 (x=0.13) tetragonality increased with Sn ions doping. Temperature dependence of the dielectric properties for Sn~(2+) ions doped (Ba_(1-x)Ca_x)TiO_3 ceramic sample showed a tetragonal-to-cubic phase transition temperature of 155 ℃, which is higher than that of undoped (Ba_(1-x)Ca_x)TiO_3 (135 ℃). By using synchrotron x-ray absorption near-edge structure spectroscopy the valence state of Sn ions in the (Ba_(1-x-y)Ca_xSn_y)TiO_3 (x=0.13, y=0.05) ferroelectric ceramics was identified to be Sn~(2+).