Composition and temperature-induced structure evolution in Bi _0.5Na _0.5TiO ₃-based solid solutions

In this study, the temperature and composition dependence of the dielectric, ferroelectric properties, and polarization current characteristics of the (0.935 - x)Bi _0.5Na _0.5TiO ₃-0. 065BaTiO ₃-xSrTiO ₃ (BNBSTx) with x ranging from 0.02 to 0.22 were systematically investigated. At elevated temperature the BNBSTx solid solution with x < 0.18 underwent a transition from ferroelectric to short-range displacement order and then to non-polar phases. The corresponding transition temperature decreased with Sr content x increasing and the critical composition x was determined to be around 0.18-0.22. In addition, the maximum-permittivity temperature T _m, which exhibited broad peaks with nearly frequency-independent behavior, almost disappeared for x > 0.18, which may be related with the formation of certain sublattices in the complex solid solution.