Synthesis and tunable luminescence properties of SrY₂O₄:Dy³⁺ phosphors

In this study, SrY₂O₄:Dy³⁺ phosphors were synthesized using the solid-state reaction method and evaluated after heat treatment at 1300 °C for 5 h. XRD analysis confirmed the orthorhombic structure of SrY₂O₄ with residual Y₂O₃ present. The addition of Dy³⁺ ions caused lattice expansion, impacting grain size and crystallinity. SEM images showed that the phosphor particles had irregular shapes with minimal size variation, although they tended to agglomerate due to high-temperature heat treatment. Optical analysis revealed significant absorption and emission peaks, with a strong excitation band in the 200–306 nm range and prominent sharp peaks in the 306–480 nm range, particularly at a 0.5 mol% doping concentration. Emission spectra indicated the highest intensity at 0.5 mol% Dy³⁺ concentration, with intensity decreasing due to concentration quenching at higher levels. Thermal stability tests showed peak emission intensity at 70 °C, with stability maintained up to 190 °C before notable thermal quenching. Chromaticity coordinates remained within the warm white region at both temperatures. This study provides detailed insights into the effects of Dy³⁺ doping on the structural, optical, and thermal properties of SrY₂O₄ phosphors. Compared to previous studies on rare-earth-doped SrY₂O₄ phosphors, this work is the first to systematically explore the substitution of Y³⁺ ions with Dy³⁺ ions until full replacement. The study not only confirmed that the highest emission intensity occurs at 0.5 mol% Dy³⁺ concentration, but also demonstrated that Dy³⁺-doped SrY₂O₄ phosphors exhibit excellent thermal stability, with emission stability maintained below 150 °C. These findings expand the potential applications of Dy³⁺-doped SrY₂O₄ phosphors, particularly in high-temperature environments and solid-state lighting.