**2.6 Lead magnesium niobate (PMN)**

Single crystal of Pb (Mg1/3Nb2/3) O3 (PMN) materials belongs to the FE relaxor materials and are used in [99], and the work in the electrostrictive actuators with high-strain and capacitor with high dielectric constant [100–102]. The Perovskite type structure of Pb (B1, B2) O3 formula with lower valence B1 such as Zn2+, Mg2+, Fe3+ and Ni2+ and higher valency B2 is such as Ta5+, Nb5+ and W5+. On cooling below the Curie temperature relaxor PMN ferroelectrics shows a wide dispersive and the diffused phase transition. Heterogeneity in composition on a microscopic scale leads to the diffuse phase transition in the relaxor ferroelectric.

In micoregion the stoichiometry is not obeyed by disorder B-site leads to change in FE transition temperatures leads to broadening dielectric peak. Strong frequency dependent dielectric constant has been observed in the relaxor ferroelectric. Curie temperature changes linearly with frequency with high dielectric loss below this temperature. Some relaxor shows second order phase transition. This relaxor remnant polarization is starting to decrease from Curie temperature and becomes zero with the increasing in temperature [103–106].
