Synthesis and characterisation of CuI·Cu2O·TeO2·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){xCu2O·(1−x)[yTeO2·(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 most compositions α-CuI crystallites are stabilized at room temperature as confirmed by XRD and HRTEM. The highest ionic conductivity at 298 K is ∼3×10−4 S cm−1. The Arrhenius plots show a break in the temperature range 294±5 K with σ 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 conduction 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 0.36–0.61 and 0.44–0.72 for systems with M=Mo and W, respectively. The average fraction of non-bridging oxygen (NBO) is higher than that in the corresponding oxide glasses without the CuI dopant.