Electron paramagnetic resonance and X-ray diffraction study of PbF2 fine powders mechanochemically doped with Er3+ ions

Abstract

Investigation of the mechanochemical doping of PbF₂ powders with Er³⁺ ions with electron paramagnetic resonance and X-ray diffraction is presented. In the analysis of the results a possibility of the structural transformation between the cubic β-PbF₂ and orthorhombic α-PbF₂phases in the course of synthesis was taken into account. It is shown that regardless of the initial state of PbF₂ it reveals high efficiency of the mechanochemical doping with Er³⁺ ions. Obtained particles are found in (α/β)-PbF₂ structurally inhomogeneous state with the majority of the Er³⁺ ions located in the equilibrium α-PbF₂ fraction. Preferrable location of the Er³⁺ ions in the α-PbF₂ phase is related to the fact that the formation of the cation vacancies necessary for a mechanically activated diffusion of erbium ions into the particles and nucleation of the α-PbF₂phase proceed in parallel and is mediated by dislocations created in the course of synthesis. Annealing of the sample leads to a conversion of its entire volume into the metastable β-PbF₂phase with all the Er³⁺ centers possessing the cubic symmetry.