Diffuse first-order phase transition in NaNbO3:Gd

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 that is diffuse over a wide temperature interval. The area of the thermal hysteresis loop was found to depend both on annealing and cooling temperatures. Optical studies in polarized light show a decrease of the domain sizes at this phase transition. The results obtained are fitted assuming a spatial distribution of Curie temperatures.