New data on the isomorphism Cu-Fe in sulphides of stannite family

11 compounds of the isomorphous series “Cu₃SnS₄” – Cu₂FeSnS₄ (kuramite-stannite) were synthesised by vacuum melting from elements. Four structures of Cu_3-xFe_xSnS₄ (x∼0.3, 0.6, 0.8, and 1.0) have been determined using Rietveld method. The sp.group I https://www.w3.org/1998/Math/MathML"> 4 ¯ https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003077503/b78de917-66fa-4aaa-8b8d-c04c8103370e/content/inq_chapter257_1075_1.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> , not I https://www.w3.org/1998/Math/MathML"> 4 ¯ 2 m https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003077503/b78de917-66fa-4aaa-8b8d-c04c8103370e/content/inq_chapter257_1075_2.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> , is maintained in all structures. Based on structure refinement and Mössbauer spectroscopy the new scheme of isomorphic replacement Cu-Fe in sulphides of stannite family is proposed. The valence state of Fe in Cu_3-xFe_xSnS₄ is changed depending on its content in the phase. The data obtained could be explained only with the supposition that the isomorphous replacement follows the order: 2Cu²⁺ → Fe³⁺ at 0< x<0.45 and Cu¹⁺ + Fe³⁺ → > 2Fe²⁺ at 0.45<x<0. Therewith the vacations are formed in tetrahedral positions, and ions of Fe³⁺ occupy the part of octahedral positions 8j.