Temperature variation of electrical conductivity and absorption edge in Cu7GeSe5I advanced superionic conductor

Single crystals of Cu7GeSe5I superionic conductor were grown by chemical transport. Their electrical conductivity in the frequency range 1.0×106–1.2×109 Hz and in the temperature range 196–295 K was measured. Cu7GeSe5I crystal is shown to exhibit a rather high electrical conductivity (σ295=64.0 S/m at 295 K) and a low activation energy (ΔEa=0.125 eV). Optical absorption edge of Cu7GeSe5I crystals in the temperature range 77–300 K was studied, the temperature dependences of the optical pseudogap and Urbach energy being obtained. The effect of different types of disordering on the Urbach absorption edge and electron–phonon interaction parameters was investigated.