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

A new series of layered oxides, Li3(Li1.5xFe3−(x+1.5x)Tex)O6, (0.1 ≤x≤ 1.0) possessing rocksalt 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, Li3(Li1.5Fe0.5Te)O6, (a= 5.1834(1); b= 8.8858(2); c= 5.16840(8) A; β= 110.660(1)∘) confirmed the stabilization of (Li1.5Fe0.5Te1.0 O6)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. Li3(Li1.5Fe0.5Te)O6 and Li3(Li0.75Fe1.75Te0.5)O6 oxides exhibited Curie–Weiss behaviour in the temperature range of 50–300 K with negative ? values. Their respective ionic conductivities were found to be 6.76×10−5 S cm−1 and 2.21 × 10−6 S cm−1 at 573 K. The UV-visible diffuse reflectance measurements for the different members of the series Li3(Li1.5xFe3−(x+1.5x)Tex)O6, 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.