Mössbauer study of isomorphous substitutions in Cu₂Fe_1-xCu_xSnS₄ and Cu₂Fe_1-xZn_xSnS₄ series

The investigation of isomorphous substitutions in minerals of stannite group was carried out for two series Cu₂FeSnS₄ – Cu₃SnS₄ (stannite – kuramite) and Cu₂FeSnS₄ – Cu₂ZnSnS₄ (stannite – kesterite) by ⁵⁷Fe and ¹¹⁹Sn Mössbauer spectroscopy. The calculation of the lattice contribution to the electric field gradient tensor at the ⁵⁷Fe nuclei and an estimation of the quadrupole shift for the determination of Fe³⁺ atom positions in the structure were carried out. The charge and structural states of Fe and Sn atoms in compounds of the two systems were determined. The schemes of isomorphous substitutions were found for both series in all range of iron concentrations. The changes in the covalence degree of the bonds Fe²⁺ − S, Fe³⁺ − S and Sn⁴⁺ − S in the process of the substitution were found.