Subsolidus equilibria in the system ZnSMnSCulnS2

Four new compounds are described. They are formed exclusively by tin IV. Two derivatives of Eu II are obtained: Eu₃Sn₂S₇, for which the crystal structure was previously described, and Eu₂SnS₄, which has a new structure. These compounds are isostructural with the corresponding Sr derivatives. Two other compounds simultaneously contain the two europium valencies II and III: Eu₅Sn₃S₁₂ (or Eu″₃Eu?₂Sn₃S₁₂) and Eu₄Sn₂S₉ (or Eu″₂Eu?₂Sn₂S₉). Their structures are described. For Eu₅Sn₃S₁₂, the two valencies of the europium are in different sites. In contrast, for Eu₄Sn₂S₉, the two valencies of the europium cannot be distinguished and are in the same sites (mixed valency). The surroundings of the europium are generally the same in these compounds (trigonal dicaped prism), and only the interatomic distances change according to the valency of the europium. The surroundings of tin IV are extremely variable: tetrahedral in the compounds formed by divalent europium; octahedral in the Sm₂SnS₅ compound, isostructural with the hypothetical Eu₂SnS₅ where Eu should be trivalent; and intermediate in the compounds containing the two Eu valencies.