Effect of Ni/Nb on structure, electrical and ferroelectric properties of 0.5PNN-0.5PZT ceramics

The solid solutions of lead nickel niobate (PNN) and lead zirconate titanate (PZT), with general formula 0.5 Pb(NixNb1-x) O-3-0.5 PZT, where x = 1/3, 1/2 and 2/3 and Zr/Ti = 50/50, were prepared by conventional solid state reaction technique. The perovskite phase formation and morphology were examined by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. From microstructure investigations, the grain size was found to lie in the range of 0.2-1.1 mu m. Diffuse phase transition and dielectric relaxation was obtained for all three compositions. The nature of dielectric relaxation was investigated through complex plane Argand plot or Cole-Cole plot. It was found that both grains as well as grain boundary contribute to dielectric relaxation. A direct correlation between the grain size and electrical properties was obtained. The remnant polarization and grain size were found to follow the inverse relationship. The inverse relationship between remnant polarization and grain size was established.