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 → 7FJ 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.