Quantitative Description of the Diffuse Phase Transition of BNT-NKN Ceramics

A perovskite solid solution of (1-x)(Bi0.5Na0.5)TiO3-x(Na0.5K0.5)NbO3 (BNT-xNKN) (x = 0-0.08) synthesized by solid state reaction technique exhibits diffuse phase transition (DPT) behavior. Power law, Gauss-type quadratic law and Lorenz-type quadratic law was employed to characterize the dielectric permittivity peaks near T-m. The diffuseness parameters gamma, delta(G) and delta(A) increase with the increase in the value of x, which implies a composition-induced diffuse transition. Among these laws simulating dielectric response in diffusion ferroelectric phase transition, the Lorenz-type quadratic law is the best to describe the characterization of DPT behavior in such a wide temperature range as observed in our experiment.