Elastic Constants and Vickers Hardness of Lead Borate Glasses

The elastic constants and Vickers hardness of B2O3-PbO glasses have been determined. The data obtained for Vickers hardness, isotropic wave velocities, bulk modulus, shear modulus and Young's modulus are listed in Table I and II together with the density and molar volume. The variation of these data with composition of the glasses are shown in Fig. 1∼3. It can be seen that both the elastic constants and Vickers hardness increase with increasing PbO content up to its maximum value at about 42 mole percent PbO and then decrease; that is, beyond this further addition of PbO produces a softer glass. The increase of the elastic constants and hardness in the composition range of approximately 20∼42 mole percent PbO is interpreted based on the evidences that the four-co-ordinated borons are present and the type of lead-oxygen association becomes more covalent bonding.