Distribution of Tb³⁺ and Eu³⁺ Photoluminescence Activator Ions in the C-Ln₂O₃ Cationic Sublattice

The samples of the C-Y₂O₃ compounds doped with photoluminescence activators Tb³⁺ and Eu³⁺ with the concentration of 3 and 3.5 mol %, respectively, have been synthesized via the sol-gel method and annealed at 800 and 1200°C. Investigation of the luminescence spectra has revealed that, in contrast to the C-Gd₂O₃ matrix, in the case of C-Y₂O₃ the increase in the annealing temperature leads to the change of the intensity of the emission bands (doublets at 483–492 and 542–550 nm for Tb³⁺; 595 and 612 nm for Eu³⁺), their ratios being almost unchanged. This fact indicates that the sample crystallinity is increased with the increase in the annealing temperature, but no redistribution of Tb³⁺ and Eu³⁺ cations in the cationic C_3i and C₂ sublattices of the matrix occurs. Far-infrared spectroscopy data has shown that the molecular structure remains unchanged as well.