Structural characteristics and dielectric response of some zinc tellurite glasses and glass ceramics

The structural characteristics of a system of optically transparent xZnO(1- x)TeO2 glasses, with x = 0.1, 0.2, 0.3 and 0.4 (mole fraction) obtained by conventional melt-quenching technique and heat treated glass ceramics were studied with X-ray diffraction (XRD), micro-Raman and infrared spectroscopy (FTIR) techniques. The dielectric spectroscopy measurements were performed over the temperature range of 100 K to 360 K and frequency range from 40 Hz to 2 MHz. The as-prepared transparent yellow glasses were found to turn into opaque (white) glass ceramics when heat treated at three temperatures (350 degrees C, 440 degrees C and 505 degrees C); the temperatures were chosen on the basis of DTA data of the base glasses. The XRD patterns of the glasses treated above 350 degrees C show the formation of crystalline phases of Zn2Te3O8, Zn(TeO3) and TeO2. The FTIR and the Raman spectra, obtained using an excitation line of 532 nm, are in agreement with the structural changes inferred from the X-ray data. Dielectric relaxation phenomena were observed in these samples and correlated with the heat treatment parameters. (c) 2012 Elsevier B.V. All rights reserved.