Anomalies of Dielectric Response in Mixed Ferro-Glass Phase of Potassium Tantalate Doped by Lithium

Abstract

The measurements of dynamic dielectric response and dc-electric field nonlinear susceptibility in K1−x Li x TaO3 for x = 0.01; 0.016 and 0.03 at 4 ≤ T ≤ 150 K has been performed. It was founded that the field decrease the susceptibility ϵ′ for the two smaller x. For x = 0.03 both the decrease (E > 1 kV/cm) and increase (E < 0.5 kV/cm) of ϵ′ value was revealed. The observed dependence of the position of ϵ′ maxima on temperature and frequency was described by Arrhenius and Vogel–Fulcher law respectively for x = 0.01, 0.016 and x = 0.03. The theoretical description was performed in random field theory framework. The calculations fitted pretty good the experimental data. It was shown that the Arrhenius law is related to the behavior of dipole glass state while Vogel–Fulcher law is the characteristic feature of mixed ferro-glass phase with coexistence of short- and long-range polar order. Therefore the measurements of dielectric response in any disordered ferroelectrics, including relaxors, can be used for identification of ferro-glass phase.