Some physical properties of lead borate glasses. I. Influences of heat treatment and PbO content

Lead borate glasses (LBG) of composition (x)PbO:(100-x)B 2 O 3 with x=8, 12, 14, 16, 20 and 24 mol.% have been prepared. The structural analysis of the prepared samples was carried out using X-ray diffraction, differential thermal analysis (DTA) and infrared spectroscopy (IR). The X-ray diffraction results revealed that the amount of crystalline phase present was <5%. Two exothermal peaks, due to crystallisation, appeared at around 669 and 860 K in the DTA curves of LBG containing 20 mol.% PbO. The IR analysis indicated that both ionic and covalent bonding of lead ions are probable; the broad absorption band around 3400 cm -1 was assigned to O-H stretching. The effects of heat treatment and PbO content on the microhardness (H v ) and DC electrical resistivity ( rho ) were investigated. The observed increase in H v with increasing PbO content was attributed to the compacting role of Pb in the glass structure. The temperature (T) range for measuring rho was 353-583 K. The reciprocal temperature dependence of log rho was classified into three regions. In the low-temperature region, 416-434 K, the conduction was of ionic type with protons as charge carriers and an Arrhenius relation controls the rho (T) dependence. The transition region, 434-487 K, is explained physically and mathematically by a new model in a subsequent paper. In the high-temperature region (HTR), 487-583 K, the ionic conduction proceeded and the Arrhenius equation was fulfilled. In this region oxygen ions were the charge carriers for glasses containing