Diffuse first-order phase transition in NaNbO$_3$:Gd (a report)

TL;DR

This study investigates the diffuse first-order phase transition in NaNbO3:Gd crystals around 150°C, revealing temperature-dependent hysteresis, domain size reduction, and a distribution of Curie temperatures.

Contribution

It reports the first observation of a diffuse first-order phase transition in NaNbO3:Gd and models the transition using a space distribution of Curie temperatures.

Findings

Phase transition occurs near 150°C with wide thermal hysteresis.

Domain sizes decrease at the phase transition.

Transition behavior fits a model with distributed Curie temperatures.

Abstract

Dielectric permittivity measurements show that (1-x)NaNbO3-(x)Gd1/3NbO3 crystals, at $x=0.09$, exhibit a first order phase transition near 150 C which is diffuse over a wide temperature interval. The area of the \epsilon(T) thermal hysteresis loop was found to depend both on the annealing and cooling temperatures. Optical studies in polarized light show the decrease of the domains sizes at this phase transition. The results obtained are fitted assuming the space distribution of Curie temperatures.