Structure and Metastability of MF<inf>2</inf> (M = Ca, Sr, Ba) Fine Powders Mechanochemically Doped with Er³⁺ Ions

Abstract

© 2015, Springer-Verlag Wien. In the paper thermal treatment investigations of the MF<inf>2</inf> (M = Ca, Sr, Ba) fine powders mechanochemically doped with Er³⁺ ions using electron paramagnetic resonance and X-ray diffraction are presented. It is shown that the prepared samples are found in the nonequilibrium metastable state characterized by the high concentration of the cationic vacancies and prevalence of the cubic symmetry-doped Er³⁺ ion centers. Vacancies formed when the deformation exceeds the elastic limit serve both as the means for a nonlocal charge compensation and a route for mechanically activated diffusion. Annealing brings the powders to the ground state with the most of the vacancies healed and the trigonal symmetry of the impurity Er³⁺ centers in SrF<inf>2</inf> and BaF<inf>2</inf> due to the local compensation by the interstitial fluorine ion.