Synthesis and characterization of new rocksalt superstructure type layered oxides Li4.5M0.5TeO6 (M(III) = Cr, Mn, Al, Ga)

• First time synthesis and characterization of layered Li4.5M0.5TeO6 (M(III)  = Cr, Mn, Al, Ga).
• Edge shared honeycomb structure formed mostly by TeO6 and (Li/M)O6 (M(III) = Cr, Mn, Al and Ga).
• Shifts in the absorption edges in consistent with the colors of the polycrystalline samples.
• Li4.5M0.5TeO6 (M(III) = Cr, Mn, Al, Ga) oxides exhibited moderate ionic conductivities in the temperature range 373–573 K.

Oxides of stoichiometry Li4.5M0.5TeO6 (M(III) = Cr, Mn, Al, Ga) have been synthesized by the solid state method and are characterized for the first time. The Rietveld refinements of the PXRD measurements confirmed the structure to be similar to the Li3(Li1.5Fe0.5Te)O6 (S.G. C2/m; a ∼ 5.183 Å; b ∼ 8.885 Å; c ∼ 5.168 Å; β ∼ 110.6°) oxide. The oxides undergo ion-exchange reactions with Ag+ ions. UV–vis diffuse reflectance measurements showed the variation in the band gaps in consistent with the colors observed from brown, brick red to white respectively for Cr3+, Mn3+ and Al3+ or Ga3+ containing oxides. The stabilization of Li4.5M0.5TeO6 (M(III) = Cr, Mn, Al, Ga) obtained by varying the alkali metal (Li+) ions together with other M3+ ions and Te6+ ions forming the edge shared octahedral layer in the rocksalt ordered structures yet again shows the rich compositional versatility of AMO2 type oxides.

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