Determination of the quasistatic linear and non-linear dielectric response in relaxor materials

Abstract Temperature dependence of the first e 1 and third harmonic dielectric response e 3 in relaxor systems was studied both as a function of the dc electric field by utilising the charge accumulation technique and as a function of the ac electric field. Additional non-linear contribution was found in the ac field dependence of e 1 in lead magnesium niobate single crystals and in lanthanum-modified lead zirconate titanate ceramics. This dominating contribution in the field dependence of e 1 ( ω ) has an origin in the fact that the increasing field shifts the relaxor state from the glassy to a particular crossover state in the glassy-to-ferroelectric crossover region. This was confirmed by quasistatic measurements of the total third-order non-linear dielectric response e 3 t as a function of the dc electric field throughout the glassy-to-ferroelectric crossover region. It is shown that the total third-order non-linear dielectric response can be understood within the extended spherical random bond-random field model of relaxor ferroelectrics.