NEW BARIUM NIOBIUM SULFIDES .1. COMPOUND WITH APPROXIMATE COMPOSITIONBANB5.67S10.8

A new barium niobium sulfide has been prepared by controlling the part ial pressure of sulfur. The single phase of the sulfide could be synth esized at 1000 degrees C when the chemical composition was maintained at x = 5.67 in BaNbxSy and the sulfur partial pressure at 23.7 kPa. Th is sulfide has a homogeneity range with the variation of the Ba and Nb ratio. The range of the homogeneity varies with the sulfur partial pr essure in the preparation. The X-ray powder diffraction pattern of thi s sulfide could be indexed on the basis of a hexagonal cell with the l attice parameters of a = 0.33363(2) nm and c = 1.7680(2) nm. The elect ron diffraction pattern, however, reveals superspots which are diffuse in the a-b* plane and streak ill the c* axis. The sulfide exhibits t emperature independent paramagnetism. In addition to this sulfide, six more new sulfides were found in the composition of 2.8 < x < 10.1 in BaNbxSy. The preparation of those compounds with single phase has not succeeded yet.