Thermal and structural studies on TeO2 substituted (PbO)0.5(P2O5)0.5 glasses

(PbO)(0.50)(P2O5)(0.50-x)(TeO2)(x) and (PbO)(0.50-y)(P2O5)(0.50)(TeO2)(y) glasses with 0.0 less than or equal to x less than or equal to 0.2 and 0.0 less than or equal to y less than or equal to 0.2, were prepared by conventional melt-quench method and characterized by P-31 magic angle spinning nuclear magnetic resonance (MAS NMR), Infrared (IR) and Differential Thermal Analysis (DTA) techniques. For (PbO)(0.50)(P2O5)(0.50-x)(TeO2)(x) glasses, there is a systematic conversion of Q(2) structural units of P to Q(1) structural units and the glass transition temperature is found to increase systematically with increase in TeO2 content as revealed by DTA. Unlike this behavior for (PbO)(0.5-y)(P2O5)(0.5)(TeO2)(y) glasses, the P-31 MAS NMR patterns are found to be unchanged and the glass transition temperature is found to decrease slightly due to TeO2, substitution. There is no P-O-Te type of linkage present in both series of glass as revealed by P-31 MAS NMR and IR studies. The observed increase in the T-g and crystallization temperature for (PbO)(0.5)(P2O5)(0.5-x)(TeO2)(x) glasses, compared to binary (PbO)(0.50)(P2O5)(0.50) glass, is attributed to the interaction of TeO2 with PbO structural units and the nucleation of Pb2P2O7 crystalline phase in the glassy matrix. (C) 2004 Published by Elsevier B.V.