Temperature behaviour of optical absorption edge and phase transitions in Cu6PS5I0.8Cl0.2 superionic mixed crystals

Abstract

Isoabsorption and spectral temperature studies of absorption edge of Cu₆PS₅I_0.8Cl_0.2 superionic mixed crystals are performed. Phase transition temperatures are determined and the transitions are identified. The optical absorption edge shape is studied in the temperature range 77–320 K, the parameters of electron-phonon interaction, resulting in the Urbach behaviour of the optical absorption edge, are determined, temperature dependences of the optical pseudogap and Urbach energy are obtained.
Keywords: superionic mixed crystals, optical absorption edge, Urbach rule, phase transitions
PACS: 78.40.Ha, 77.80.Bh