X-ray structural study of the layered compounds CoxNbS2

X-ray intensity measurements have been performed on the structure of the layered compound CoxNbS2 single crystals (x≤0.5) at room temperature. The c-axis lattice parameter changes discontinuously at around x=0.2 and remains constant with further increase of the Co content. For the lower content of Co atoms (x<0.2), no diffuse maxima appeared on the (hk0) and (hk1) reciprocal lattice planes. At x=0.23, the diffuse maxima are clearly seen at 4/3, 4/3, 1 and 5/3, 5/3, 1 reciprocal lattice points. At x=0.32, sharp intensity maxima appear at 4/3, 4/3, 0 and 5/3, 5/3, 0 in addition to at 4/3, 4/3, 1 and 5/3, 5/3, 1. It is understood that 3×3R30∘ ordered structure exists at the stoichiometric composition of x=1/3. At further increasing the Co content, the intensity at 4/3, 4/3, 0 and 5/3, 5/3, 0 is weakening and disappears above x=0.4. The structural model based on the space group P6322 (No. 182) for CoxNbS2 (x>0.4) is discussed with considering both the position of the Co atoms and their occupation rate.