Elastic Properties and the Short- and Medium-Range Structures of Lead Silicate Glasses

Abstract

The elastic moduli and their pressure and temperature derivatives of lead silicate glasses were measured by the cubic resonance method and pulse superposition method. Thermal expansion coefficients and heat capacities were also measured The sound velocities, Young's modulus, shear modulus decreared monotonously with increasing PbO content, but the bulk modulus increased with increasing PbO content up to its maximum at about 50mol% PbO and then decreased remarkably. The compositional dependence of bulk modulus was interpreted based on the change in the role of Pb2+ ions in glass structure. That is, Pb2+ ions behave as a network modifier for PbO content 50mol%. The short- and medium-range structures in lead silicate glasses were discossed in terms of the three-band theory using characteristic temperatures obtained from the specific heats. It was found that the medium-range order in lead silicate glasses increased with increasing PbO content. The elastic anomaly in fused silica with negative pressure and positive temperature derivatives disappeared with increasing PbO content. Lead silicate glasses with PbO content>40mol% showed no elastic anomaly. The characteristic temperature representing the intermolecular bonding of the glass network was found to affect the pressure and temperature derivatives of elastic moduli.