The high-temperature plastic -phase, with a face-centered cubic structure, was stabilized at ambient temperatures by programmed quenching of the melt and by the addition of a few percent of lithium carbonate, in order to arrest the cubic-to-monoclinic phase transformation. The resultant metastable phase was characterized by using X-ray diffraction techniques (a = 0.698nm), differential scanning calorimetry (revealing endothermic humps at 351 and 542C), alternating-current conductivity, infra-red and electron spin resonance spectroscopic techniques. It was found that the electrical conductivity of this phase was enhanced by about 6 orders of magnitude, relative to the insulating monoclinic phase with an activation energy of 0.4eV. The microcrystalline phase which was obtained by quenching from 300C exhibited a 2-slope Arrhenius plot (1.13 and 0.05eV) with an intermediate knee. The activation energy for high-temperature conductivity decreased from 1.13 to 0.18eV during prolonged isothermal annealing. This suggested that molecular relaxation led to the optimization of Li conduction paths. The infra-red spectra reflected quenched-in disorder by a broadening of the peaks which were characteristic of SO42- and of the stabilizing CO32- ions. The electron spin resonance spectra of quenched material after X-irradiation revealed microscopic evidence, for dynamically disordered CO32-, which included an intense isotropic (g = 2.009) spectrum that was characteristic of a tumbling CO3- radical.

P.Balaya, C.S.Sunandana: Journal of the Physics and Chemistry of Solids, 1994, 55[1], 39-48