Effects of Mn doping on dielectric properties of ferroelectric relaxor PLZT ceramics

Abstract

A series of PLZT (8/65/35) ceramics with different Mn2O3 concentration (0.01, 0.1, 0.3, 1.0, and 3.0% by weight) have been synthesized to figure out its influence on their dielectric properties. The complex dielectric permittivity ε* = ε′−iε″ as function of frequency and temperature as well as polarisation loops P(E) have been studied as a function of Mn concentration. It was found that Mn doping is restrained the Vogel-Fulcher law held in the unmodified PLZT compound producing essential change of the dependence of ε* on temperature and frequency and of the shape of P(E). The observed effects are explained by gradual involvement of Debye and Maxwell-Wagner polarisation mechanisms in relaxation processes with the growth of the concentration of Mn concentration admixture. A decrease of the ε'(T) maximum value and shift of the maximum to higher temperatures is observed. The observed effects are attributed to impacts of Mn2+ and Mn3+ ions: formation of oxygen vacancies paired with Mn2+ as dipoles and Jahn-Teller distortion prompted by Mn3+ ions.