ELECTRON-RADIATION DAMAGE AND LI-COLLOID CREATION IN LI2O

Polycrystalline samples of Li2O were irradiated with 1-MeV electrons a t different temperatures, T-irr, in the range 21 to 275 K, and their e lectron paramagnetic resonance spectra measured. The created defects m anifest a strong T-irr dependence. (i) At low temperatures, T(irr)less than or equal to 200 K, mainly F+ centers (O vacancies with a trapped electron) are formed; thermal annealing leads to their recovery near T-ann=400 degrees C, which is accompanied by the emergence of a new si gnal near g=2.003, possibly due to their agglomeration into small Ft c lusters. The latter disappear at 600-700 degrees C. (ii) At T-irr=200 K, the F+ spectra are superimposed by the g=2.003 line and by a new na rrow signal at g=2.0023, probably already caused by small metallic col loids. (iii) At T-irr=275 K, finally, only a narrow T-independent line (Delta H similar to 10(-2) mT) is observed at g=2.00235(2), character istic for metallic Li colloids. The microwave dielectric constant, eps ilon, measured on the same specimens increased notably after the room- temperature irradiation emphasizing the presence of metallic particles , while remaining unchanged for lower T-irr. Both the colloid line and the radiation-induced Delta epsilon vanish simultaneously above T-ann approximate to 250 degrees C.