Synthesis, structure and luminescence properties of a anion-substituted germanates Ca₂La_7.2Eu_0.8(GeO₄)_6–x(PO₄)_xO_2+x/2 with an apatite-type structure

Abstract

The aim of this research work is to study the effect of substitution in the anionic lattice of inorganic phosphors activated by Eu3+ ions with an apatite-type structure of [GeO4]4– by [PO4]3 groups on their luminescent and crystal chemical properties. A number of solid solutions with the general formula Ca2La7.2Eu0.8(GeO4)6–x(PO4)xO2+x/2–δ (1) have been synthesized. The reduction of Eu3+ to Eu2+ in the structure of synthesized crystal phosphors has been shown by methods of luminescent spectroscopy and electron paramagnetic resonance (EPR). For compounds with x = 0.18 and 0.48, the effect of the composition on the strength of the crystal field acting on Eu3+ ions is shown. The phonon sublattice was studied using IR and Raman spectroscopy methods. A decrease in the integral luminescence intensity is shown for the selected type of illumination. The obtained data can be used to create effective phosphors for such technological fields as the creation of scitillation detectors, television devices and photodiodes.