Structure and physical properties of glassy lead vanadates

Abstract

The structure and physical properties of the lead-vanadate glasses of compositions (V₂O₅)_x(PbO)_100-x with x=50-90 mol %, prepared by the roller-quenching technique have been studied. It has been shown by x-ray diffraction, scanning electron microscopy, density and oxygen molar volume measurements, etc., that single-phase homogeneous glasses with a random network structure can be obtained in this system. The network structure is built up of unaffected VO₅ groups as in crystalline V₂O₅ and affected VO₅ groups. A gradual decrease in the coordination number of V⁵⁺ and V⁴⁺ ions and the formation of nonbridging oxygen atoms have been observed with increasing V₂O₅ content in the glass compositions, consistent with the decrease in density. The nearly equimolar glass composition devitrifies to crystalline metavanadate PbV₂O₆. However, glasses with higher V₂O₅ content devitrify to PbV₂O₆ and a V₂O₅-rich amorphous phase. The fine structure of the electron spin resonance hyperfine lines observed when the glass composition is equimolar, gradually reduces to a two-component structure at the same effective g value and is interpreted as due to an increase of the hopping rate of polarons with increasing V₂O₅ content in the glass compositions.