Induced crystallization and the physical properties of PbO–Sb 2O 3–As 2O 3: MoO 3 glass system

Abstract

PbO–Sb 2O 3–As 2O 3 glasses mixed with different concentrations of MoO 3 (ranging from 0 to 1.0 mol%) were crystallized. The samples were characterized by X-ray diffraction, scanning electron microscopy and differential thermal analysis techniques. The X-ray diffraction and the scanning electron microscopic studies have revealed the presence of Pb 5Sb 2O 8, PbSb 2O 6, SbAsO 4, Sb 2MoO 6, Sb 4Mo 10O 31, As 4Mo 3O 15, Pb 5Sb 4O 11 crystalline phases in these samples. The differential thermal analysis indicated that the surface crystallization prevails over the bulk crystallization as the concentration of the crystallizing agent is increased. The infrared (IR) spectral studies exhibit bands due to MoO 4 structural units in addition to the conventional bands due to various antimonate and arsenate structural groups. The studies on PbO–Sb 2O 3–As 2O 3: MoO 3 glass-ceramics with respect to various physical properties viz., dielectric properties over a range of frequency and temperature, optical absorption, electron spin resonance (ESR) and magnetic susceptibility at room temperature have also been reported. The optical absorption, ESR and magnetic susceptibility studies indicated that the molybdenum ions exist in Mo 5+ state in addition to Mo 6+ state in these samples. The redox ratio found to increase as the concentration of the MoO 3 is increased. 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.