Evolution of polar order in Ba (Ti_{1 - x} Sn_x) O₃ ceramics

The ferroelectric hysteresis loops of Ba(Ti_0.85Sn_0.15)O₃ and Ba(Ti_0.75Sn_0.25)O₃ solid solution ceramics covering the temperature T_m of a dielectric permittivity peak were investigated. At temperatures ∼100 K lower than their respective T_m, the two compositions present clear ferroelectricity. Comparing with the parent ferroelectric BaTiO₃, the tiny hysteresis loop of both Ba(Ti_0.85Sn_0.15)O₃ and Ba(Ti_0.75Sn_0.25)O₃ ceramics at temperatures above T_m reveals the existence of polar order regions or microdomains. The dielectric properties of the two solid solutions are different: the former shows the character of diffuse ferroelectric phase transition, while the latter displays the feature of relaxor ferroelectrics. According to their ferroelectric properties, however, Ba(Ti_0.85Sn_0.15)O₃ and Ba(Ti_0.75Sn_0.25)O₃ compositions exhibit the diffuse transition from low-temperature ferroelectric domains to polar nanoregions during the ε (T) peak area. A difference between the two compositions is that the diffuse transition of the former takes place in a much narrower temperature range than that of the latter.