Synthesis and characterisation of CuI center dot Cu2O center dot TeO2 center dot MO3 (M = Mo or W) glass systems

Glasses based on the ternary oxide system Cu2O-TeO2-MO3 (M = Mo or W) doped with CuI were synthesized according to the formula zCuI . (1 - z){xCu(2)O . (1 - x)[yTeO(2) . (1 - y)MO3]} (M = Mo, z = 0.3, 0.4 and 0.5 and M = W, z = 0.3 and 0.4, respectively) in vacuum or argon atmosphere using the twin- roller quenching technique. The glasses exhibit phase separation and in mos t compositions a-CuI crystallites are stabilized at room temperature as con firmed by XRD and HRTEM. The highest ionic conductivity at 298 K is similar to 3 X 10(-4) S cm(-1). The Arrhenius plots show a break in the temperatur e range 294+/-5 K with sigma increasing from 10(-5) S cm(-1) to 10(-4) S cm (-1). The conductivity below 294 K and above 295 K is due to the ionic cond uction by Cu+ in the oxide glass matrix and the halide phase, respectively. DSC studies do not show any phase transition in the region 294+/-5 K. FTIR study indicates that the IR bands of glasses are not affected by doping of CuI. XPS studies show that the fractional area of Cu 2p peaks [Cu+/(Cu+ Cu2+)] are in the range 0.35-0.61 and 0.44-0.72 for systems with M = Mo and W, respectively. The average fraction of non-bridging oxygen (NBO) is high er than that in the corresponding oxide glasses without the CuI dopant. (C) 2000 Elsevier Science B.V. All rights reserved.