Role of chromium ion valence states in ZnO-As2O3-Sb2O3 glass system by means of spectroscopic and dielectric studies

ZnO-Sb2O3-As2O3 transparent glasses containing small concentrations of chromium ions (introduced as Cr2O3) ranging from 0 to 0.2 mol% is prepared. A number of studies viz., XRD, SEM, DTA, optical absorption, FT-IR, Raman, ESR spectra, magnetic susceptibility and dielectric properties (constant epsilon', loss tan delta, ac. conductivity sigma(ac) over a wide range of frequency and temperature as well as dielectric breakdown strength at room temperature) of these glasses have been carried out as a function of chromium ion concentration. The results have been analysed in the light of different oxidation states of chromium ions. The analyses indicates that when the concentration of chromium ions is low, these ions mostly exist in Cr6+ and Cr5+ states, occupy network forming positions with CrO42- and CrO43- structural units respectively and increase the rigidity of the glass network. When the concentration of chromium ions is gradually increased, these ions seem to be existing mostly in Cr3+ state. (C) 2010 Elsevier Ltd. All rights reserved.