SYNTHESIS, STRUCTURE, AND ELECTRICAL-PROPERTIES OF A NEW FAMILY OF MIXED-METAL SULFIDES CONTAINING RUTILE-LIKE [INS4]INFINITY [TIS4]INFINITY CHAINS - (RE)(6)IN1-XTI1+XS12 (RE=ND, SM, GD)/

Via iodine vapor-flux reactions, single crystals of a new family of mi xed-metal sulfides in the pseudoternary (RE)(2)S-3-In2S3-Ti2S3 systems were isolated. The general formula of these phases can be written as (RE)(6)In1-xTi1+xS12, where RE/x = Nd/0.22 (1), Sm/0.16 (2), Gd/-0.26 (3), and Gd/0.86 (4); Z = 2. The single-crystal X-ray diffraction stud ies showed that these sulfides crystallize in the Pnnm (No. 58) space group. The cell constants are as follows: 1: a = 13.716 (2) Angstrom, b = 16.267 (2) Angstrom, c = 3.917 (2) Angstrom, V = 873.9 (3) Angstro m(3); 2: a = 13.597 (3) Angstrom, b = 16.200 (2) Angstrom, c = 3.857 ( 3) Angstrom, V = 849.7 (7) Angstrom(3); 3: a = 13.530 (2) Angstrom, b = 16.265 (4) Angstrom, c = 3.854 (4) Angstrom, V = 848 (1) Angstrom(3) ; 4: a = 13.429 (8) Angstrom, b = 16.109 (6) Angstrom, c = 3.785 (8) A ngstrom, V = 819 (2) Angstrom(3). The title compounds are isostructura l with Sm3InS6, where the two crystallographically independent indium sites are substituted in a preferential manner by titanium(III) cation s. The frameworks are quasi-one-dimensional resulting from a juxtaposi tion of [InS4](infinity)/[TiS4](infinity) chains. The parallel chains are interconnected by rare-earth cations, (RE)(3+). The nearest Ti-Ti interaction corresponds to the shortest crystallographic axis, i.e., d (Ti-Ti) = C, across shared edges of octahedra. Four-probe resistivity measurements on single crystals show a simple semiconducting behavior with a slight departure toward an insulating state at low temperatures . A brief discussion about the electronic behavior and its correlation with the structure is presented.