Polycrystals of -spodumene were studied by using impedance spectroscopy (0.1Hz to 235GHz) at temperatures ranging from 5 to 500K. At high temperatures, the Li ions were mobile and led to direct-current and alternating-current conductivity. These were analyzed, in terms of a universal dielectric response, by using the modulus formalism. At low temperatures, or very high frequencies, dielectric losses which were due to a dipolar freezing process were observed. The latter closely resembled an orientational glass transition. In order to confirm the glassy nature of this material, measurements were made of the low-temperature specific heat at 3 to 50K. This provided evidence for the existence of the excess contributions that were usually observed in amorphous materials.

R.Böhmer, P.Lunkenheimer, M.Lotze, A.Loidl: Zeitschrift für Physik B, 1996, 100[4], 583-93