Syntheses, Structures, and Characterization of Quaternary Tellurites, Li3MTe4O11 (M = Al, Ga, and Fe)

Three new quaternary lithium metal tellurites, Li3MTe4O11 (M = Al, Ga, and Fe), have been synthesized through hydrothermal and solid-state reactions by heating a mixture of LiOH·H2O, TeO2, and M2O3. The structures of the title compounds have been determined by single-crystal and powder X-ray diffraction. Li3MTe4O11 reveal three-dimensional (3D) frameworks that consist of MO6 octahedra, TeO3 trigonal pyramids, and TeO4 polyhedra. The variable coordination mode of Te4+ within the framework leads to the formation of 1D channels that host Li+ cations on both tetrahedral and octahedral sites. The bulk and grain boundary Li+ ion conductivities for a Li3FeTe4O11 pellet in open air are estimated to be 1.0 × 10–4 and 2.7 × 10–6 S cm–1, respectively, at room temperature from the impedance profile analysis. A lower activation energy of 19.9 kJ mol–1 is obtained for the system, which is similar to that of Li10GeP2S12 (24 kJ mol–1). Detailed characterizations such as thermal, spectroscopic, and magnetic properties for the reported materials are also reported.