Crystal structure and electrical properties of the mixed valent titanium oxysulfide Sm2Ti2S2O4.5

摘要

A new phase Sm2Ti2S2O4.5 was synthesized and its crystal structure was solved by single-crystal X-ray diffraction. This compound crystallizes in the monoclinic system (C2/m) with lattice constants a = 17.9987(11) Angstrom, b = 3.71607(14) Angstrom, c = 12.6172(8) Angstrom and beta = 133.645(4)degrees. The structure is built up from double chains of Ti-centered octahedra between which Sm-polyhedra develop. In spite of very close formulations, the structure Of Sm2Ti2S2O4.5 differs completely from that of the defect Ruddelsden-Popper phase Sm2Ti2S2O5 previously reported. The title compound presents a mixed valence for titanium with Ti(III) (d(1)) and Ti(IV) (d(0)) located in different crystallographic sites. However, conductivity measurements show that this compound is non-metallic. (C) 2004 Elsevier Inc. All rights reserved.