Study of radiation damage inLi2O by means of electron-spin resonance

Abstract

ESR spectra with a hyperfine structure consisting of more than 20 peaks were observed in Li/sub 2/O single crystals, irradiated by energetic tritons and helium ions formed by 6 x 10/sup 22/ to 6 x 10/sup 25/ /sup 6/Li(n,..cap alpha..)-/sup 3/H reactions per m/sup 3/ introduced with the order of 10/sup 20/ to 10/sup 23/ thermal neutrons per m/sup 2/. The g value of the spectra was 2.002 +- 0.001, and the hyperfine structure depended on the orientation of the specimens relative to the applied magnetic field. From the angular dependence the spectra were attributed to F/sup +/ centers (an oxygen vacancy trapping an electron). In Li/sub 2/O single crystals irradiated to the order of 10/sup 23/ thermal neutrons per m/sup 2/, colloidal Li metal centers were not observed, in direct contrast with the situations in sintered Li/sub 2/O pellets. Isochronal and isothermal annealing experiments were done and the recovery behavior of the F/sup +/ centers was observed. From the isothermal annealing experiments, the activation energy for recovery of the F/sup +/ centers was determined to be about 135 kJ/mol (1.4 eV).