Synthesis and ferroelectric properties of rare earth compounds with tungsten bronze-type structure

Abstract

Polycrystalline materials with a general formula Pb 2Na 0.8R 0.2Nb 4.8Fe 0.2O 15 (R = Dy, Eu, Sm, Nd, La) have been synthesized, in air by a high temperature solid state reaction method. X-ray diffraction study, at room temperature, revealed that they crystallize in the tungsten bronze-type structure. Dielectric properties were performed, in the temperature range 25–500 °C, at three different frequencies 10, 100 and 1000 kHz. The ferroelectric transition is pronounced by a large thermal hysteresis during the heating and cooling cycles. The determined Curie temperature values T c were discussed as a function of rare earth size. Phase transitions around T c for the investigated compounds were confirmed by differential scanning calorimetry (DSC) measurements.