Structure and ionic conductivity of rapidly quenched AgI-Ag₂WO₄ superionic conductor glasses

Silver ion conducting glasses composed of (AgI)_x-(Ag₂WO₄)_1-x (x = 0.80-0.55) were prepared by a rapid melt quenching method. Their physical properties were investigated by X-ray, DSC, impedance and Ag-109 NMR measurements. The glass transition temperatures were in the range from 110°C to 187°C. The glasses show unusually high ionic conductivities of 2.5 × 10^-3 S/cm at x=0.55 and 2.3 × 10^-1 S/cm at x=0.80, which varied exponentially with increasing AgI content. Ag-109 NMR spectra also support the high mobility of silver ions in the glasses. Structures of the glasses were investigated by FTIR and W-L₁ edge XANES. From these results it is concluded that the tungsten ions are octahedrally coordinated by oxygen ions as in crystalline Ag₂WC₄ and Ag₂₆I₁₈W₄O₁₆, which is quite different from the structure of AgI-Ag₂MoO₄ glasses.