Reassessment of Li colloid production and characterization in irradiated Li2O

Poly- and monocrystalline Li2O samples have been irradiated by 1 and 2.5 Me V electrons at various doses and temperatures and their EPR spectra measure d. At low doses, less than 10(19) e(-)/cm(2), and for T-irr < 150-200 K, th e spectra contain a 0.2 mT broad line at g = 2.0035(3), recovering at 650 d egrees C, which is due to non-metallic F-center agglomerates and which corr esponds to that observed by Noda et al. (Rad. Eff. 97_(1986) 297) in ion- a nd neutron-irradiated Li2O. For higher doses and higher T-irr, the spectra contain signals at g = 2.0023(1) caused by metallic Li colloids. The latter exist in two sizes, much less than 1 mu m and much greater than 1 mu m, re presented by a Lorentzian and a Dysonian signal, respectively; the former a nnealing at 300 degrees C, the latter near 450 degrees C. Optical microscop y on semi-transparent crystals indicates that the large colloids are disk-s haped and oriented along {1 1 1}. (C) 1998 Elsevier Science B.V. All rights reserved.