Sol–Gel–derived YVO₄: Eu with eco-friendly chelating agent: Study of the emission under near-UV and X-ray excitation

The optical properties of Eu-doped YVO₄ particles synthesized by the modified sol–gel method using an ecological chelating agent were investigated under both UV and X-ray excitation. Phase composition, morphology, and luminescent behavior were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray fluorescence (XRF), X-ray absorption near-edge structure (XANES), photoluminescence spectra (PL), and X-ray-excited optical luminescence (XEOL). XRD analysis confirmed a single-phase tetragonal zircon structure formation. From Rietveld refinement calculations, a subtle difference in lattice parameters with slight flattening of the unit cell and an increase in its volume was observed with increasing europium concentration and an average nanometric crystallite size was estimated for all samples. TEM images revealed particles with different shapes, with average sizes a little larger than the nanometric limit (100 nm). XRF and XANES analyses confirmed homogeneous doping and a stable unique 3+ valence state for europium. PL and XEOL spectra showed characteristic Eu³⁺ f–f transitions, with the 5 D₀→ 7 F₂ transition as the dominant emission. XEOL spectra exhibited enhanced 5 D₁→ 7 F J transitions related to higher excitation energy. Chromaticity diagrams indicated red emission under UV excitation and a reddish orange emission under X-ray excitation, supporting the potential use of this material in LEDs and other luminescent devices with the possibility of identifying the excitation energy range. A crystal field analysis was carried out through the simple overlap model and the method of equivalent nearest neighbor.