Syntheses, Structures, and Characterization of Quaternary Tellurites, Li 3 MTe 4 O 11 (M = Al, Ga, and Fe).

Three new quaternary lithium metal tellurites, Li3 MTe4 O11 (M = Al, Ga, and Fe), have been synthesized through hydrothermal and solid-state reactions by heating a mixture of LiOH·H2 O, TeO2 , and M2 O3 . The structures of the title compounds have been determined by single-crystal and powder X-ray diffraction. Li3 MTe4 O11 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 Li3 FeTe4 O11 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 Li10 GeP2 S12 (24 kJ mol-1 ). Detailed characterizations such as thermal, spectroscopic, and magnetic properties for the reported materials are also reported.