Effect of Synthesis Conditions on the Luminescence of Europium-Containing Materials Based on Yttria and Yttrium Oxyfluorides

Resumo

We have studied the luminescence of europium(III)-doped materials based on yttria and yttrium oxyfluorides. The materials were prepared through heat treatment of fluorine-containing yttrium and europium(III) thioacetamide complexes at temperatures of 400, 600, and 800°C for 2 to 6 h. The products were shown to consist of (Eu_хY_{1 –х})F₃, (Eu_хY_{1 –х})₅O₄F₇, (Eu_хY_{1 –х})OF, and (Eu_хY_{1 –х})₂O₃ phases. We have proposed a scheme that reflects the formation sequence of the main components of the materials in the above temperature range. Narrow-band luminescence of the materials has been shown to arise from Eu³⁺⁵D₀ → ⁷F_j electronic transitions. The origin of the observed broad luminescence band peaking in the range 480–500 nm can be understood in terms of surface structural defects, the particle size, and the broad particle size distribution. The luminescence spectrum has been shown to be influenced by the starting-mixture composition, synthesis conditions, host composition, and excitation wavelength. Some of the observed luminescence features have been shown to be due to the effect of S^2– ions in the composition of europium-containing activator centers.