Li2TeO4: Structural characterization and ionic conductivity measurements of a new tellurate

A new tellurate Li2TeO4 (Li2TeO4-LT) was synthesized via a conventional solid-state route from specific precursors, LiOH.H2O and H6TeO6. The cell, initially identified as tetragonal from X-ray powder diffraction at room temperature, was finally found to be orthorhombic thanks to thermal X-ray powder diffraction. The space group, Pbcn, was determined with the help of electron diffraction while the structure was obtained from neutron powder diffraction (a = 5.0106(3), b = 11.5369(8) and c = 5.0057(4) angstrom. As the tellurate (3-Na2TeO4, its structure is built from TeO6 octahedra sharing edges forming thus infinite chains [TeO4]n2n-parallel to the c axis. These chains are separated from each other by Li+ ions in octahedral coordination. Contrary to (3-Na2TeO4, Li2TeO4-LT does not capture CO2 and presents a modest ionic conduction (300 degrees C, T = 1.8 10-8 S cm-1), lower than the tetragonal Li2TeO4 variety (300 degrees C, approximate to 10-6 S.cm-1). In addition, a complete solid solution Na2-xLixTeO4 was evidenced.