X-Ray, Optical and Dielectric Studies of Diffused Phase Transitions in NaNbO₃-Based Solid Solution Crystals

Abstract

In flux-grown (1−x)NaNbO₃-(x)Gd_1/3NbO₃ solid solution crystals a diffusion of the dielectric permittivity ϵ maximum grows with x and increases dramatically when x exceeds a threshold value x₀ ≈ 0.1. Optical studies by the rotating-polarizer method show that Gd-doping results in a very small mean size of twins and the distribution of the birefringence image becomes very messy. In the x < x₀ range the changes of lattice parameters and birefringence corresponding to the ϵ(T) anomaly were revealed. The results obtained are in line with the assumption that phase transition diffusion in NaNbO₃ is a result of the local strains stemmed from the impurities.

Keywords:

• Antiferroelectrics
• diffuse phase transitions
• perovskites
• relaxors