The orthorhombic phase of Ti6Sn5 in the Ti-Sn binary system is regarded as a low-temperature or metastable phase. The motivation of the present study was to clarify the presence of this orthorhombic phase. This phase could not be synthesized by heating a mixture of Ti and Sn powder at 873 K, whereas single crystals of a novel suboxide, Ti6Sn5O0.88 (orthorhombic, a = 5.72790(10) Å, b = 9.1379(2) Å, c = 16.9275(3) Å, space group Immm), were obtained by heating powders of Ti, Sn, and TiO2 at 1273 K in an Ar atmosphere, followed by slow cooling. Crystal structure analysis of single-crystal X-ray diffraction data indicated that the O atoms are located at a 4 g site in the Ti tetrahedron of the orthorhombic Ti6Sn5 structure. An almost single-phase polycrystalline bulk sample of Ti6Sn5O0.9 was prepared by heating a compacted powder mixture of Ti, Sn, SnO2 at 1173 K. The bulk sample exhibited metallic electrical properties.
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