Composition and temperature-induced structure evolution in Bi_0.5Na_0.5TiO₃-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_0.5TiO₃–0.065BaTiO₃–xSrTiO₃ (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.