engleski

Electrical and optical absorption studies of Cu_7GeS_5I fast-ion conductor

Electrical conductivity and fundamental absorption spectra of monocrystalline Cu_7GeS_5I were measured in the temperature ranges 95-370 K and 77-373 K, respectively. A rather high electrical conductivity (sigma = 6.98x10^-3 ohm^-1cm^-1 at 300 K) and low activation energy (deltaE_a = 0.183 eV) was found. The influence of different types of disordering on the Urbach absorption edge and electron-phonon interaction parameters were calculated, discussed and compared with the same parameters in Cu_7GeS_5I, Cu_6PX_5I (X=S, Se) and Ag_7GeX_5I (X=S, Se) compounds. We have concluded that the P->Ge and Cu->Ag cation substitution results in an increase of the electrical conductivity and a decrease of the activation energy. Besides, P->Ge substitution, results in complete smearing and disappearance of the exciton absorption bands and in blue shift of the Urbach absorption edge, an increase of the edge energy width and an electron-phonon-interaction enhancement.

Fast-ion conductors; Electrical conductivity; Urbach absorption edge; Structural disorder.

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