X-ray Diffraction Analysis of the PbO–SiO<SUB>2</SUB> System in the Glassy and the Molten State

Abstract

The structures of glassy and molten states in the PbO–SiO2 system were investigated by X-ray diffraction analysis. In the glass, the Pb–O bond has the ionic charactor in the SiO2-rich region and has more of the covalent charactor with increasing PbO concentration. The atomic distance of Pb–Pb pair, 0.375 nm, is not changed with changing PbO concentration, and Pb atoms are considered to be arranged with local order in the glass. The Pb–Pb peaks in the SiO2-rich region correspond roughly to multiples of 0.374 nm, and Pb atoms seem to be arranged in a simple and straight chain. However, the arrangement probably tends to consist of twisted and zigzag PbO4 chains with increasing PbO concentration.In the molten state, a part of the three-dimensional network structure of covalent Pb–O bond seems to be destroyed and, the concentration of Pb2+ ion which is free in the melt increases. Then Pb–Pb pairs with the distance around 0.50 nm increase due to increase in straight chains such as ionic Pb2+–O2−–Pb2+ which hardly exist in the glass.