Preparation and transport studies of the new superionic system (CuI) x·[(Ag 2O) 3·(B 2O 3)] 100− x (35 ⩽ x⩽75)

Abstract

Efforts were made to prepare high conductivity superionic solids in the mixed system (CuI) x ·[(Ag 2O) 3·(B 2O 3] 100− x where x= 35, 40, 45, 50, 55, 60, 65, 70 and 75 mol% respectively, by melting the appropriate solid mixtures and then quenching them to low temperatures. Powder specimens of these compositions were analysed using differential scanning calorimetric (DSC) and X-ray diffraction (XRD) techniques. These studies have confirmed the formation of new products as revealed by the absence of diffraction peaks of parent materials in the XRD patterns. Among the various compositions, a significant number are found to contain AgI since DSC traces have indicated the characteristics β-α-phase transition temperature of AgI around 420 K. Detailed temperature-dependent electric conductivity studies on these materials by ac impedance analysis in the frequency range 65.5 kHz1 Hz and over the temperature range 293–398 K have clearly indicated the occurrence of high silver ionic conductivities. It is found that the highest electrical conductivity of 2.14×10 −3 S cm −1 and a silver ion transport number of 0.96 at 305 K could be achieved for the composition, 40 CuI45 Ag 2 O15 B 2 O 3 which exhibits a low activation energy of 24.1 kJ/mole in the temperature range of investigation.