Dielectric,ferroelectric and optical behaviour of terbium hydrogen tartrate trihydrate crystals

Gel diffusion technique, using agar–agar as gel medium, has been employed to obtain single crystals of terbium hydrogen tartrate trihydrate. The grown crystals are characterised by X-ray diffraction, scanning electron microscopy, CHN technique, thermogravimetric methods and UV–Vis spectroscopy. Dielectric, ferroelectric and optical studies on this metal–organic compound have been carried out. The dielectric constant has been measured as a function of temperature and frequency in the ranges of 20–250 °C and 20 Hz–3 MHz, respectively. The study of dielectric behaviour as a function of temperature reveals two dielectric anomalies at 95 and 198 °C. The dielectric anomaly at 95 °C is suggested to be due to ferroelectric phase transition brought about in the material. The study of polarisation versus electric field shows a hysteresis loop which thereby confirms the ferroelectric nature of terbium hydrogen tartrate trihydrate crystals. The dielectric anomaly at 198 °C is suggested to be due to loss of water molecules in the compound. The results of thermal study show that the material is thermally stable up to temperature of about 200 °C. Optical studies show that the terbium hydrogen tartrate trihydrate crystal has good transparency in the entire visible and infra red range of the spectrum.