NEUTRON-SCATTERING STUDY OF LITHIUM-OXIDE

The thermal vibrations of lithium oxide were studied in the temperatur e rang from 293 to 1120 K using a high-resolution powder diffractomete r. The isotropic thermal parameter of the oxygen ion has a linear rela tionship with the temperature. The parameter of the lithium ion increa ses rapidly above 450 K. To clarify the nature of the thermal vibratio n of lithium ion, inelastic neutron scattering measurements for a tran sverse optical mode were also carried out in the temperature range fro m 293 to 1000 K. No temperature dependence of the phonon energy was ob served for the TO mode at the zone center, while for the Raman-active mode the phonon energy has a strong temperature dependence above 450 K .