Electric Double Hysteresis in (K_x Na_1-x)NbO₃ Single Crystals

Abstract

SODIUM niobate forms solid solutions of perovskite type structure with the niobates of potassium¹, cadmium² and lead³. At quite low concentrations of the latter in these compositions the room temperature orthorhombic antiferroelectric structure of pure sodium niobate (NaNbO₃) gives place to an orthorhombic ferroelectric form. The phase-change between these two structures has not, however, been observed in any of these systems. In the ceramic specimens which have been examined, the ferroelectric properties increase gradually over a range of compositions. Pure sodium niobate single crystals, on the other hand, show double hysteresis loops at high fields⁴ suggesting a discontinuous change to a ferroelectric form.