Phase transitions and dielectric properties in A-site ion substituted (Na1/2Bi1/2)TiO3 ceramics (A=Pb and Sr)

The dielectric permittivity of A-site ion substituted $({\mathrm{Na}}_{\text{1/2}}{\mathrm{Bi}}_{\text{1/2}}){\mathrm{TiO}}_3\mathrm{(A=Pb,Sr)}$ solid solutions has been investigated with the aid of structural analysis. As the addition of PT increased, the first order characteristics of the phase transition appeared. In contrast, additions of ST made the solid solution exhibit relaxor ferroelectrics behavior. Microscopic structural analysis revealed that the dielectric properties were determined by cation ordering which controlled the translational symmetry and domain configuration. In the NBT–PT solid solution, A-site cations were randomly redistributed and macrodomains formed. However, the addition of ST distributed A-site cations with local ordering and divided the domains of NBT into micropolar regions. The contrasting effects of the addition of the Pb and Sr cations on the dielectric properties of NBT are discussed in terms of the polarizability and the tolerance factors as they relate to the perovskite structure.