Tellurate Mixtures Li//2ZrTeO//6 and Li//2HfTeO//6: a New Order Phenomenon in the Corindon Family. .

Article abstract of DOI:10.1016/0022-4596(88)90309-X

Li//2ZrTeO//6 and Li//2HfTeO//6, synthesized at 700 degree C, are hexagonal-rhombohedral, space group R3, with a equals 5. 172 (5. 164) Angstrom and c equals 13. 847 (13. 782) Angstrom for Zr(Hf). Their structure, deduced from X-ray powder diffraction intensities, may be derived from that of LiNbO//3 by an additional Zr(Hf)-Te ordering. The order phenomena exhibit two components: (i) within each octahedral layer there is a Li/Zr(Hf) or a Li/Te order, and (ii) two adjacent layers are connected by pairs of face-sharing octahedra, alternatively a Li-Zr(Hf) and a Li-Te. Measurements of the dielectric properties point to a diffuse ferroelectric transition near T//c equals 660 degree C for Li//2ZrTeO//6. Their Raman and IR spectra are reported and discussed in terms of symmetry properties and mass effects.