Lithium ion behavior in lithium oxide by neutron scattering studies

Lithium ion behavior in lithium oxide, Li2O, was studied in the temperature range from 293 K to 1120 K by the High-Resolution Powder Diffractometer (HRPD) installed in the JRR-3M. The diffraction patterns were analyzed with the RIETAN program. At room temperature, the thermal parameters related to the mean square of the amplitude of vibration of the lithium and the oxygen ions were 6 x 10-21m2 and 4 x 10-21m2, respectively. AT 1120 K the thermal parameter of the lithium ion was 34 x 10-21m2. On the other hand, the parameter of the oxygen ion was 16 x 10-21m2. Inelastic neutron scattering studies for the lithium oxide single crystal were also carried out on the triple-axis neutron spectrometers installed at the JRR-2 and the HFIR. Although the value of a phonon energy of a transverse acoustic mode (Σ3) at zone boundary was 30.6 meV at room temperature, this value was decreased to 25.1 meV at 700 K. This large softening was caused by anharmonicity of the crystal potential of lithium oxide. (author)