Hardening in LiF induced by fast Ni ions and recovery of properties under annealing

Abstract

The recovery of hardness and optical absorbance of LiF crystals irradiated with 640 MeV nickel ions under annealing at 450-810 K is investigated. Recovery of the hardness of irradiated crystals is initiated at temperatures above 530 K, at which a transition from a complex absorption spectrum to a spectrum with only one broad peak at 275 nm is observed. Activation energy of 0.13 eV ± 0.02 eV, which is close to that necessary for migration of H centers, is obtained from the annealing data. -5]. However, so far the nature of radiation defects responsible for hardening (possibly small Li colloids, clusters of molecular fluorine and vacancies) is not clearly identified. A study of thermal stability of these defects and recovery of hardness and optical absorbance by thermal annealing of LiF crystals irradiated with fast nickel ions is reported hereafter.

A review of colour center and nanostructure creation in LiF under heavy ion irradiation

“…The observed difference in the behaviour of hardening and accumulation of F centers is comprehensive because hardening, according to the Hobbs model, is based on the evolution of the dislocation structure with the participation of H centers. Also, the decomposition of the dislocation structure and the recovery of hardness under annealing is limited by the mobility of H centers [67].…”