Evidence of Jahn-Teller distortion in Li_xMn₂O ₄ by thermal diffusivity measurements

Thermal diffusivities of Li_xMn₂O₄ (x=0.9, 1.0 and 1.1) polycrystalline pellets are determined by photoacoustic technique in the reflection configuration, at two temperatures, 298 K and 280 K, above and below their Jahn-Teller phase transition temperature (290 K). The diffusivities of Li_xMn₂O₄ at 280 K show a drastic reduction from their corresponding room temperature values (298 K) and the percentage of reduction in the thermal diffusivity for Li_xMn₂O ₄ increases with their Li content. These effects are associated with the reduction in crystal symmetry due to structural deformation by Jahn-Teller distortion observed in Li_xMn₂O₄ below its transition temperature.