Spectroscopic studies of the structure of Na2O-CdO-PbO-P2O5 metaphosphate glasses

Density, molar volume, glass transition temperature, infrared spectroscopy and Raman spectroscopy measurements have been carried out for the glasses having mol% composition (40-z)Na2O.10CdO.zPbO.50P(2)O(5) (0less than or equal tozless than or equal to40). The density of these glasses was found to be in the range 2(.)79-4(.)58 g cm(-3). The molar volume decreases with increasing PbO concentration. Substitution of CdO and PbO for Na2O increases T-g. FTIR spectroscopy reveals the formation of P-O-Cd and P-O-Pb bonds. The formation of P-O-Cd and P-O-Pb bonds, which replace P=O-...Na+ bonds while keeping the same fraction of P-O-P bonds, increases the cross-link density in the glass network and therefore increases the T, of the glasses. The Raman results are in agreement with the FTIR analyses. A structural model for these glasses was suggested on the basis of infrared and Raman spectral investigations and by comparing with known metaphosphate glass structures.