Interesting cationic (Li+/Fe3+/Te6+) variations in new rocksalt ordered structures

A new series of layered oxides, Li-3(Li1.5xFe3-(x+1.5x)Tex)O-6, (0.1 <= x <= 1.0) possessing rock-salt superstructures crystallizing in monoclinic (S.G. C2/m) symmetry is reported here. Investigations based on single crystal and powder X-ray diffraction studies for the x = 1 member, Li-3(Li1.5Fe0.5Te)O-6, (a = 5.1834(1); b = 8.8858(2); c = 5.16840(8) angstrom; beta = 110.660(1)degrees) confirmed the stabilization of (Li1.5Fe0.5Te1.0O6)(3-) honeycomb arrays with a very high amount of lithium ions. The structure for the x = 0.5 member (Li3.75Fe1.75Te0.5O6) has also been confirmed by the powder X-ray diffraction Rietveld refinements. Li-3(Li1.5Fe0.5Te)O-6 and Li-3(Li0.75Fe1.75Te0.5)O-6 oxides exhibited Curie-Weiss behaviour in the temperature range of 50-300 K with negative theta values. Their respective ionic conductivities were found to be 6.76 x 10(-5) S cm(-1) and 2.21 x 10(-6) S cm(-1) at 573 K. The UV-visible diffuse reflectance measurements for the different members of the series Li-3(Li1.5xFe3-(x+1.5x)Tex)O-6, (0.1 <= x <= 1.0) show the expected shifts in their absorption edges based on the increasing amount of Fe3+ ions starting from x = 1.0 member to x = 0.1 member.