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.