ION-TRANSPORT STUDIES IN PBI2-AG2O-V2O5 GLASSY SYSTEM

New glasses in the system xPbI(2)-(100 - x)(2Ag(2)O-1V(2)O(5)), 5 less than or equal to x less than or equal to 20, have been prepared and c haracterized by X-ray diffraction and differential scanning calorimetr y. Variations of conductivity with composition, frequency, and tempera ture has been investigated. Conductivity of the glasses increases with increase in mole% of PbI2 and attains a value of 1.4 x 10(-3) ohm(-1) cm(-1) at 300 K for x = 20. IR spectroscopy studies on these glasses indicate that the oxyanion network is unaffected by the addition of Pb I2. The transport number of Ag+ determined by the e.m.f. method is 0.9 9. The diffusion coefficient of Ag+ ions in x = 10 mole% of PbI2 with Ag-111 as the radioactive tracer was found to be 9.5 x 10(-9) cm(2) s( -1) at 363 K. The frequency dependence of electrical conductivity for various glass compositions at different temperatures has been analysed in terms of Jonscher's universal expression. The above studies along with the data on density, molar volume and carrier concentration of Ag + and I-, indicate the formation of 'AgI clusters' due to co-ordinate exchange between Pb2+ and Ag+, contributing to high Ag+ ion conductivi ty.