FE-57-MOSSBAUER SPECTRA, ELECTRONIC AND CRYSTAL-STRUCTURE OF MEMBERS OF THE CUS2-FES2 SOLID-SOLUTION SERIES

Members of the (Cu, Fe)S2 solid solution crystallize in the pyrite str ucture type, space group Pa 3, Cu and Fe being statistically distribut ed on the metal sites. Within this series, a semiconductor to metal tr ansition can be detected between 25 and 38 mole% CuS2 . Compositional dependent Fe-57-Moessbauer spectra reveal Fe2+ in low-spin configurati on. A minimum of the quadrupole splitting and the slope in the Fe-57-i somer shift in the intermediate part of the system, near 30 mole% CUS2 , can be correlated with the onset of metallic conductivity, whereas t he structural parameters are not influenced by this transition. The an alysis of the compositional dependency of the quadrupole splitting, in comparison to the isotypic system (Co, Fe) S2, leads to the conclusio n that Cu in solid (Cu, Fe)S2 compounds is Cu+ with an Ar-3 d10 electr onic configuration.