ULTRASONIC AND THERMAL PROPERTIES OF BORATE AND PHOSPHATE GLASSES DOPED WITH BISMUTH AND LEAD

Abstract

A systematic series of (B₂O₃,P₂O₅)-Bi₂O₃-PbO glasses have been successfully prepared by using the rapid quenching technique where each oxides contents change for every series based on their weight percentage. Their amorphous natures were confirmed earlier by the X-ray diffraction technique. The experimental results show that the density of both glasses, determined by using the Archimedes’ principle, increase with glass modifier content. This is due to the replacement of Bi₂O₃ and PbO in the borate and phosphate glassy networks. The molar volume for borate glass increases with addition of bismuth and lead oxides, however a reverse trend occurs for the phosphate glass. The longitudinal and shear ultrasound velocities, determined by the MBS 8000 system, of both lead bismuth borate and phosphate glasses show decreasing trend as more PbO and Bi₂O₃ are being added into the glass system. The increase in PbO/ Bi₂O₃ content was probably related to the progressive increase in the concentration of non-bridging oxygen (NBOs). Thermal studies of the glass, using Labsys DTA - Setaram machine, show that values for glass transition temperature (T_g) is closely related to the chemical bond in the system. In lead bismuth borate glasses, the addition of more Pb²⁺ and Bi³⁺ will result in the ionic bond character became more dominant in the system and hence decreases the T_g of sample. However, in lead bismuth phosphate glasses, the addition of Pb²⁺ and Bi³⁺ not only failed to weaken the covalent character in P–O–P bonds, but strengthened it further which leads to an increment in T_g values.