Mössbauer spectra of ternary tin(IV) sulphides in the systems Na2S–SnS2, BaS–SnS2, and PbS–SnS2

Abstract

¹¹⁹ Sn Mössbauer spectra have been recorded for a number of ternary sulphides isolated from the systems Na₂S–SnS₂, BaS–SnS₂, and PbS–SnS₂. The series includes compounds of known crystal structure such as Na₄SnS₄, Na₆Sn₂S₇, the high- and low-temperature forms (HT and LT) of Ba₂SnS₄, and Ba₃Sn₂S₇, all of which contain tin tetrahedrally co-ordinated by sulphur atoms; Na₂SnS₃(LT) and PbSnS₃, in which the tin is octahedrally co-ordinated; and Na₄Sn₃S₈ which contains tin in both tetrahedral and trigonal bipyramidal sites. The measurements establish that the chemical isomer shift is sensitive to the co-ordination number of the central tin atom, and decreases by ca. 0.2 mm s^–1 in going from tetrahedral, through trigonal bipyramidal, to octahedral co-ordination. The data for the compounds Na₂SnS₃(HT) and BaSnS₃, Whose crystal structures are not known, are consistent with the presence of tin in distorted tetrahedral environments.