Polycrystalline and monocrystalline samples were irradiated with 1MeV electrons at various temperatures, and their electron paramagnetic resonance spectra were measured. It was found that the created defects exhibited a strong dependence upon the irradiation temperature. At irradiation temperatures below 200K, mainly F+ centers (O-vacancies with a trapped electron) formed. At room temperature, a temperature-independent narrow signal (0.01mT) at g = 2.00235 (typical of metallic Li colloids) was observed for the first time. The microwave dielectric constant was also measured, and both components increased markedly after room-temperature irradiation. This confirmed the presence of metallic particles. It remained unchanged for lower irradiation temperatures. Thermal annealing of the specimens led to the disappearance of the colloid line above an annealing temperature of 250C. In the case of irradiation at temperatures below 200K, the recovery of F+ centers at annealing temperatures near to 400C was accompanied by the appearance of a new signal near to g = 2.003. This was suggested to be due to their agglomeration into small clusters. The latter disappeared at annealing temperatures of between 600 and 700C; depending upon the irradiation temperature.

P.Vajda, F.Beuneu: Nuclear Instruments and Methods in Physics Research B, 1996, 116[1-4], 183-6