TERNARY THALLIUM INDIUM SULFIDES - A SUMM ARY

Combined thermal and X-Ray analyses in the ternary system Thallium-Ind ium-Sulfur show, that the two binary sections Tl2S-In2S3 and TlS-InS c ontain ternary compounds with unique crystal structures. The chemical formulas of these ternary solids are TlIn5S8, TlIn3S5, TlInS2 and Tl3I nS3 for the section Tl2S-In2S3 and TlIn5S6 as well as Tl3In5S8 (metast able high temperature phase) for the section TlS-InS respectively With TlIn5S7 an additional ternary solid could be detected, which is locat ed outside the two sections. It is derived from the binary mixed valen ce compound In6S7 by complete substitution of In+ by Tl+. The followin g ionic formulations make the mixed valence character of the ternary T hallium-Indium-Sulfides reasonable: TlIn5S8 = Tl+(In3+)(5)(S2-)(8), Tl In3S5 = Tl+(In3+)(3)(S2-)(5), TlInS2 = Tl+In3+(S2-)(2), Tl3InS3 = (TlIn3+.(S2-)(3) TlIn5S6 = Tl+([In-2](4+)In3+(S2-)(6), Tl3In5S8 = 4x[(Tl)(0,75).(In+In3+(S2-)(2)], TlIn5S7 = Tl+[In-2](4+)(In3+)(3)(S2-)(7) Al l com pounds contain Tl+-ions in a characteristic ''lone pair coordina tion'' of S2- ions. Indium atoms however occur with the oxidation numb ers +2 (formal, Int dumb bells with covalent In-In bonding) and +3 (wi th In3+ in tetrahedral and octahedral coordination of S2-). Chemical p reparation, crystal chemistry and general properties of the ternary so lids are discussed, summarized and compared to each other.