Mössbauer effect studies on cubanite (CuFe₂S₃) and related iron sulphides

Abstract

The Mössbauer spectrum of the orthorhombic mineral cubanite (CuFe2S3) has been compared with those of related iron sulphides: KFeS2, CuFeS2, FeCr2S4, Feln2S4, and Cu2FeSnS4. Systematic trends of chemical isomer shift, quadrupole splitting, and hyperfine magnetic field with oxidation state and co-ordination number of the iron atoms were observed and these suggest that cubanite is Cu+Fe2+Fe3+S3 with rapid electron exchange between the ferrous and ferric ions; the hyperfine magnetic field is 332 kOe at room temperature. When cubanite is heated for two hours in vacuo at 370° a disordered cubic phase is produced which shows a broad non-magnetic Mössbauer spectrum at room temperature; this is consistent with the presence of equal numbers of non-interchanging ferrous and ferric ions in this phase.