Structural investigation of the ammonium intercalates of titanium and niobium disulfides
Abstract The ammonium intercalates (NH+4)y'TiSy'−2, y'=0.21 and 0.23, and (NH+4)0.19NbS0.19−2 have been synthesized and characterized by X-ray powder diffraction, thermogravimetric analysis, vapor pressure measurements and evolved gas analysis. These compounds have six-layer stage-II structures with rhombohedral, or nearly rhombohedral, symmetry. A comparison of calculated and observed X-ray powder diffraction intensities for ( NH + 4 ) 0.21 TiS 0.21− 2 (a=3.1416 and c=42.73 A ) shows good agreement with trigonal prismatic NH+4 coordination in the van der Waals gap. X-ray powder diffraction also suggests the presence of substantial local-layer disorder for many of these compounds, which is probably associated with the low temperatures required for synthesis.