Empirical scaling of the dielectric permittivity peak in relaxor ferroelectrics

Dielectric permittivity ɛ as a function of temperature is measured in PbMg_1/3Nb_2/3O₃ and a number of other relaxor ferroelectrics with the perovskite structure. It is found that the data taken from the high-temperature slopes of the diffused permittivity peaks of all the materials studied can be collapsed onto a single scaling line derived from the formula ɛ_A/ɛ=1+0.5(T−T_A)²/δ², where ɛ_A, T_A, and δ are the parameters depending on the composition. This formula describes the static conventional relaxor susceptibility, which provides the dominant contribution to the permittivity peak at temperatures above the temperature of the maximum. In the close vicinity of the peak temperature and below, the scaling is disturbed due to the conventional relaxor dispersion.