New, Lead Free, Perovskites With a Diffuse Phase Transition: NaNbO_{3} ~ Solid Solutions

TL;DR

This study investigates NaNbO3-based solid solutions that exhibit diffuse phase transitions and relaxor behavior, characterized by a sharp concentration-driven transition and hysteresis, explained through a Landau phenomenological model.

Contribution

It reports the discovery of a first-order phase transition to relaxor-like behavior in NaNbO3 solid solutions and provides a phenomenological explanation for the relaxor properties.

Findings

Diffuse dielectric permittivity maximum observed

Abrupt concentration phase transition identified

Hysteresis in dielectric response documented

Abstract

Some of (1-x)NaNbO_3-(x)ABO_3 perovskite solid solutions exhibit a dramatic diffusion of the dielectric permittivity epsilon' maximum and relaxor-type behavior when the second component concentration exceeds a threshold value x_0. The concentration phase transition to the relaxor-like phase is abrupt (of the first order kind) that is seen from the step in the dependence of the epsilon'(T) maximum temperature, T_m, on x. The precursor of this transition is a giant (up to 100 K) temperature hysteresis of epsilon'(T). Some relaxor-like properties appear even at x < x_0 in the course of cooling while disappear in the course of heating. The experimental data obtained are qualitatively described within a Landau-type phenomenological approach, assuming the relaxor-type behavior to be local stress-induced.