Ionic conductivity and stored energy in gamma-irradiated NaF

Abstract

Gamma irradiation reduces the ionic conductivity of NaF single crystals due to the decrease of the extrinsic cation-vacancy concentration. Irradiation also makes the binding energy of the impurity-cation-vacancy dipole higher than that for unirradiated samples. The thermal recovery of these effects takes place between 270 and , which is the range in which the main stored-energy release peak occurs. The energy released below , when the irradiated sample is heated, is . It is proposed that these processes are related to radiation-induced divacancies, that behave as traps for the impurity-cation-vacancy dipoles.

Volume expansion in heavily gamma irradiated NaCl and LiF single crystals

“…Since thermally quenched or plastically deformed samples show similar stored energy spectra to the irradiated ones, it was proposed that the energy release results from the recombination of anions and cations with divacancies [15]. Stored energy and ionic conductivity measurements on NaF support this conclusion [25]. Further studies of the lattice defects related to the stored energy release indicate that for irradiated samples they coalesce near the sample surfaces, giving rise to microcavities and some surface roughening or reconstruction, the conclusion that clusters of divacancies could account for the stored energy being again proposed [20].…”