A new solid electrolyte Na2LiFeTeO6 has been prepared by solid-state reactions in air at 700 degrees C and characterized by powder X-ray diffraction, redox titration and impedance measurements on ceramic samples. It is a new superstructure type of the well-known hexagonal layered P2 type with complete ordering of Li, Fe and Te in octahedral brucite-like layers: orthorhombic, P2(1)2(1)2(1), a = 5.2109(1), b = 8.9791(2), c = 11.2389(2)angstrom, Z = 4. At room temperature, sodium ions in the interlayer gap are concentrated in two of the six non-equivalent trigonal prisms; at elevated temperatures, they exhibit high ionic conductivity, e.g., 4 S/m at 300 degrees C. Orthorhombic distortion decreases on heating, presumably due to sodium movement, and vanishes at ca. 400 degrees C giving rise to the hexagonal Na2Co2TeO6-type structure. Analogous Na2URTeO6 (R = Al or Ga), Na2LiFeWO6, Na2Mn2TeO6, Na2M2WO6 (M = Ni or Cu), Na2NiMSbO6 (M = Al or Fe) and Na2NiAlTO6 (T = Nb or To) could not be prepared. (C) 2012 Elsevier B.V. All rights reserved.