Influence of molybdenum ions on spectroscopic and dielectric properties of ZnF2–Bi2O3–P2O5 glass ceramics

Abstract

Glasses doped with different concentrations of MoO3 (ranging from 0 to 10mol %) in the system ZnF2–Bi2O3–P2O5 were crystallized and characterized by X-ray diffraction(XRD), scanning electron microscopy (SEM) and differential thermal analysis (DTA) techniques. The presence of BiPO4, α-Zn3(PO4)2, Bi2MoO6, γ‐Bi2MoO6, Bi2Mo2O9, MoOPO4, α-ZnMoO4 microcrystalline phases were exposed by XRD and SEM studies. The DTA indicated that the surface crystallization prevails over the bulk crystallization as the concentration of the crystallizing agent is increased. Spectroscopic properties (FTIR, Raman, optical absorption and ESR) at room temperature and dielectric properties (dielectric constant, loss tanδ, ac conductivity) over a range of frequency and temperature are studied. The IR and Raman spectra exhibit bands due to MoO4 and MoO6 units in structural groups in addition to various conventional phosphate groups. The existence of Mo5+ state in addition to Mo6+ state in these glass ceramic samples has been identified by the optical absorption, ESR and magnetic susceptibility studies. The variations observed in all these properties with the concentration of the crystallizing agent have been analyzed in the light of different oxidation states and environment of molybdenum ions in the glass ceramic network.