Electrochemical properties of Ag5Te2Cl0.8Br0.2, a representative of the solid solutions Ag5Te2Cl1-xBrx

Impedance spectroscopic investigations of Ag5Te2Cl0.8Br0.2, a selected representative of the solid Solutions Ag5Te2Cl1-xBrx with x = 0-1, proved the mixed-conducting property of this class of materials. Two polymorphs are realized in the temperature range of 309 to 410 K, the monoclinic beta-phase (space group P2(1)/n) and the tetragonal alpha-phase (space group l4/mcm) with all order-disorder phase transition temperature of 336 K (DSC). A sharp increase of the total and ionic conductivity can be observed at 337 K. in good accordance with the phase transition temperature. The electronic conductivity exceeds the ionic conductivity by approximately one order of magnitude over a wide range of temperature. Conductivities are sigma(ion) =6.9 x 10(-5) (309 K) and sigma(tot) =4.80 x 10(-4) Omega(-1) cm(-1) (310 K) for beta-Ag5Te2Cl0.8Br0.2 and sigma(ion) = 1.6 x 10(-2) (395 K) and sigma(tot) = 1.73 x 10(-1) Omega(-1) cm(-1) (394 K) for alpha-Ag5Te2Cl0.8Br0.2.