Luminescent properties of solid solutions in the PbF2-EuF3 and PbF2–ErF3 systems

Abstract

New concept of phase equilibria in PbF2-REF3 (RE = Eu or Er) systems at low temperatures has been proposed. The proposed concept was experimentally approved by the study of structural and luminescent properties of solid solutions in PbF2-REF3 (RE = Eu or Er) systems with the general formula Pb1-xRxF2+x. Fluorite structures with wide homogeneity ranges were synthesized both by a solid-phase method and by co-precipitation from aqueous solutions. For the PbF2-EuF3 system, the single-phase region of the corresponding solid solutions was found to be 0–46 mol% EuF3 when synthesized by the solid-phase method and 7–53 mol% EuF3 in the case of the co-precipitation technique. The luminescent centers of Eu3+ in solid solutions obtained by the solid-phase synthesis have greater symmetry than the centers obtained by the co-precipitation. For the PbF2–ErF3 system, the crystallization region of single-phase solid solutions’ powders was 12–42 mol% ErF3 in the case of co-precipitation technique: the most intense bands in the Er3+ luminescence spectra were in the blue and green regions of the spectrum. We observed an effective anti-Stokes luminescence caused by up-conversion for the samples obtained by the solid phase synthesis of Er-based solid solutions.