Electrical properties and FTIR spectra of ZnO–PbO–P2O5 glasses

Glasses of chemical composition xZnO.(60−x)PbO.40P2O5 (x=10–60 mol%) have been prepared and investigated for FTIR, density, molar volume (Vm), and DC conductivity. Both density and molar volume decreases systematically with composition. FTIR analysis indicates that ≥30 mol% (PbO and/or ZnO) enters the glass structure as formers. Below and above that concentration a decreasing amount of Pb2+ (Zn2+) is incorporated into the network as modifier. The band at 1018–1025 cm−1 can be considered as an indication for the presence of P–O–Pb(Zn) linkages. By introducing ZnO into the glasses, P–O–Pb(Zn) linkages may be formed by opening up PO bonds of PO4 tetrahedra. For all glasses the linear dependence of the conductivity indicates an ionic conduction due to Pb2+ and/or Zn2+ ions. The increase in activation energy by about 68%, and also the decrease in the conductivity at certain temperature not only attributed to an increase in the covalency of the glass matrix upon replacing PbO by ZnO but also due to an increase in the strain energy because of the decrease in Vm of the studied glasses. It is found that the conductivity of ZnO–PbO–P2O5 glasses is four orders of magnitude higher than that of ZnO–PbO–B2O3 glasses containing the same amount of ZnO measured at the same temperature. In addition, both conductivities decrease with composition which may indicate that the origin of these decreases may be the same regardless the type of the host glass former. The differences in electronegativity and size of Zn2+ and Pb2+ divalent ions and the structural changes that will follow in the network govern the conductivity behaviour of Zn–Pb containing glasses.