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 A degrees 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 A degrees C. The dielectric anomaly at 95 A degrees 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 A degrees 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 A degrees 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.