Physical and spectroscopic features of cobalt ions in multi-component CaF2-ZnO-Bi2O3-P2O5 glass ceramics

Multi-component CaF2-ZnO-Bi2O3-P2O5 glasses doped with different concentrations of CoO (ranging from 0 to 1.0 mol %) were crystallized by heat treatment. These samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), EDS and differential thermal analysis (DTA) techniques. The XRD patterns have indicated the presence of various phases viz., Ca-3(PO4)(2), Bi3PO7, CaZn2(PO4)(2), Bi(PO4), Zn-3(PO4)(2), ZnCo(P2O7), CaCoP2O7, ZnCo2O4, CoP2, Co3O4 and CoF3. Conventional spectroscopic studies such as optical absorption, FTIR and Raman were also carried out on these glass ceramic samples. The analysis of these results has indicated that cobalt ions exist in both Co2+ and Co3+ states in the glass ceramic network. These studies have further revealed that the rigidity of the glass ceramic network decreases up to 0.6 mol% of CoO. Beyond this concentration the insulating strength of the prepared samples is found to increase. (C) 2016 Elsevier B.V. All rights reserved.