Composite Crystals BaTiSy(y= 2.70–2.93)

Abstract Barium titanium sulfide, BaTiS y ( y = 2.70–2.93), has been prepared in atmospheres in which the sulfur partial pressures are controlled. The electron diffraction spots and the X-ray powder diffraction peaks of the sulfide could not be indexed because of large periodicity. The diffraction pattern was, however, indexable on the basis of hexagonal setting (trigonal system) with the lattice parameters of a , c TiS 3 , and c Ba when four-dimensional formalism was employed. In the four-dimensional formalism, the structure could be represented as a single structure with homogeneity range of BaTiS 2.70 –BaTiS 2.93 . From the view point of three dimensional formalism, the structure of the sulfide consists of two penetrating hexagonal subcells. The lattice parameter a in the hexagonal setting is common to both subcells while c has different values, c TiS 3 and c Ba . The c TiS 3 increases with decreasing sulfur content, while c Ba decreases. As the lattice parameter c is given by c = pc TiS 3 = qc Ba , where p and q are integers, there is an infinite number of structures with different c parameters in the composition range of BaTiS 2.70 –BaTiS 2.93 .