P2O5 DOPANT IN PbO-PbCl2-CdCl2 GLASSES

3 mole% P2O5 were introduced in PbO-PbCl2-CdCl2 glasses to increase the vitrification domain. Thermal analysis indeed indicates that devitrification tendency is lowered with P2O5 addition. 207Pb NMR is in accordance with a network reticulation by P2O5 via P-O-Pb bond formation. However, 31P NMR shows that lead-cadmium orthophosphate groups are formed in the glass. These orthophosphate have a low solubility in the melt, and tend to precipitate if the quenching rate is not high enough. We conclude that P2O5 have not a stabilizing effect on the lead-cadmium oxychloride glasses.