Influence of Catalyses on the Preparation of YVO₄:Eu³⁺ Phosphors by the Sol–gel Methodology

Abstract

YVO₄:Eu³⁺ phosphors have been prepared by the hydrolytic sol–gel methodology, with and without alkaline catalyst. The solid powder was obtained by reaction between yttrium III chloride and vanadium alkoxides; the europium III chloride was used as structural probe. The powder was treated at 100, 400, 600, or 800 °C for 4 h. The samples were characterized by X-ray diffraction, thermal analysis, and photoluminescence. The XRD patterns revealed YVO₄ crystalline phase formation for the sample prepared without the catalyst and heat-treated at 600 °C and for the sample prepared in the presence of ammonium as catalyst and heat-treated at 100 °C. The average nanosized crystallites were estimated by the Scherrer equation. The sample which was produced via alkaline catalysis underwent weight loss in two stages, at 100 and 400 °C, whereas the sample obtained without catalyst presented four stages of weight loss, at 150, 250, 400, and 650 °C. The excitation spectra of the samples treated at different temperatures displayed the charge transfer band (CTB) at 320 nm. PL data of all the samples revealed the characteristic transition bands arising from the ⁵D₀ → ⁵F_J (J = 0, 1, 2, 3, and 4) manifolds under maximum excitation at 320, 394, and 466 nm in all cases. The ⁵D₀ → ⁷ F₂ transition often dominates the emission spectra, indicating that the Eu³⁺ ion occupies a site without inversion center. The long lifetime suggests that the matrix can be applied as phosphors. In conclusion, the sol–gel methodology is a very efficient approach for the production of phosphors at low temperature.