Evolution of polar order in ceramics

The ferroelectric hysteresis loops of Ba(Ti0.85Sn0.15)O3 and Ba(Ti0.75Sn0.25)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(Ti0.85Sn0.15)O3 and Ba(Ti0.75Sn0.25)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(Ti0.85Sn0.15)O3 and Ba(Ti0.75Sn0.25)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.