Insights into the local structure and optical performance of SrY₂O₄:Eu³⁺ red phosphors through Judd-Ofelt analysis

In this study, Eu³⁺-doped SrY₂O₄ red-emitting phosphors were successfully synthesized via a conventional solid-state reaction route, and their structural, optical and luminescence properties were systematically investigated. X-ray diffraction analysis confirmed the formation of a single-phase orthorhombic SrY₂O₄ host, while microscopic and spectroscopic studies revealed high crystallinity and homogeneous incorporation of Eu³⁺ ions into the lattice. Increasing the Eu³⁺ concentration from 1 to 6 mol% induced a slight lattice expansion and reduced the optical band gap from 6.13 to 5.30 eV. Under near-ultraviolet and blue-light excitation, the phosphors exhibited intense red emission dominated by the ⁵D₀ → ⁷F_J transition of Eu³⁺ ions, indicating the occupation of non-centrosymmetric lattice sites. Judd-Ofelt analysis was employed to evaluate the local environment and radiative emission properties of Eu³⁺ ions; the results indicate that Eu³⁺ ions occupy non-centrosymmetric sites with local asymmetry at C _s sites, with the Ω ₂ value increasing slightly from 2.623 × 10^-20 to 2.795 × 10^-20 cm² as the Eu concentration rises from 1% to 5%. The optimum emission intensity was achieved at 5 mol% Eu³⁺, beyond which concentration quenching occurred through non-radiative energy transfer between neighboring activator ions. The phosphors demonstrated excellent thermal stability with an average activation energy of 0.242 eV, high color purity exceeding 85%, and an internal quantum efficiency of 67.74%. These results highlight the potential of SrY₂O₄:Eu³⁺ phosphors as efficient red-emitting components for warm white light-emitting diode (WLED) technologies.