Synthesis and luminescence spectra of (Y2O3–YOF):Ln(III) composites

Abstract

Sols were prepared by reacting yttrium, europium, and terbium trifluoroacetates with thioacetamide in ethyl acetate. The Eu³⁺ and Tb³⁺ concentrations in the sols were 0.10 to 10 wt % relative to yttrium, which corresponded to 0.061 (0.059) to 6.1 (5.9) at % Eu (Tb). The sols were converted into a gel-like state by slowly evaporating the solvent. After ripening, the gels were heat-treated at a temperature of 800°C. X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, and IR spectroscopy results showed that the resultant composites consisted predominantly of a mixture of Y₂O₃ and YOF. The Eu³⁺ and Tb³⁺ ions were shown to substitute for Y³⁺ ions in the crystal lattices of the yttrium oxide and yttrium oxyfluoride. The formation of the (Eu_0.6Y_0.4)₂O₃, Eu₂O₃, and EuOF phases was demonstrated. We determined the types and parameters of the crystal lattices of the synthesized materials in relation to activator concentrations. The luminescence of the composites is due to the ⁵D₀ → ⁷F_j and ⁵D₄ → ⁷F_j electronic transitions of the Eu³⁺ and Tb³⁺ ions and depends on the host and activator compositions, the excitation wavelength, and other factors.