STRUCTURE AND PHASE-TRANSITION IN THE SPINEL SYSTEM LI-1-XCUVO4 (0 LESS-THAN-OR-EQUAL-TO X LESS-THAN-OR-EQUAL-TO 0.2), WITH ONE-DIMENSIONAL COOPERATIVE JAHN-TELLER ORDERING

Structure and phase transition in the spinel Li1-xCuVO4 were characterized by X-ray Rietveld structure refinement, magnetic susceptibility, high-temperature X-ray diffraction, and differential scanning calorimetry measurements. The nonstoichiometric Li1-xCuVO4 was synthesized in the range of 0≤x≤0.2. In the structure of Li1-xCuVO, the [CuO6] octahedra are connected to each other one-dimensionally parallel to the a axis, such that the elongated octahedral axis is ordered along the c axis. A lowtemperature modification of Li1-xCuVO4 prepared by annealing the sample at 80°C showed a phase transition near 100°C. The high-temperature phase was also quenched to ambient temperature. The Jahn-Teller distortion of the [CuO6] octahedra decreased with the increase in the non-Jahn-Teller Cu3+ ions for the low-temperature Li1-xCuVO4. Further, one-and two-dimensional cooperative ordering crystal structures have been discussed. © 1992 Academic Press, Inc.