Radiation induced movement of charge compensating ions in CaF 2

Abstract

Trivalent rare earth ions have been incorporated substitutionally in CaF 2 where charge compensation has occurred (a) by F − interstitials and O 2− substitutional ions forming complexes with the trivalent ions, or (b) by processes remote from the trivalent ions. The ESR spectra of the magnetic rare earth ions indicate the presence or absence of n.n. compensating ions, and monitor the movement of these ions from or into n.n. sites. Ion movement has been stimulated by u.v. irradiation and electron bombardment, and changes in the valence state of the rare earth ions have occurred. Thermal annealing techniques give an activation energy for F − interstitial movement of 1.0 ± 0.1 eV. The self-diffusion of oxygen in the CaF 2 lattice has been monitored in a new way.