NMR AND IR-SPECTROSCOPY STUDIES OF THE STRUCTURE OF LEAD BOROSILICATE GLASSES.

Using NMR and IR spectroscopy the authors have investigated the change of coordination of boron as a function of the chemical composition of the glasses in the PbO(ZnO)-B//2O//3-SiO//2 system. They also measured the chemical stability of these glasses in water. It is found that the ability of boron to change its coordination in borosilicate glasses is determined by the nature and quantity of the metal oxide and by the concentration of SiO//2. The structural role of lead in lead silicate glasses is determined by its concentration and by the B//2O//3/SiO//2 ratio. With a relatively low concentration, lead is a modifier, the corresponding borate and silicon-oxygen structures facilitating the formation of fourfold coordinated boron; at concentrations greater than 30 mol% it is a glass-former, i. e. , an element of the lead-oxygen network.