Second-phase-induced fluorescence quenching in non-equivalent substituted red phosphors

Concentration quenching, which generally originates from serious energy migrations among the uniformly distributed luminescent centers in the host matrix, is a key factor to influence the luminescence properties of materials. Different from previous reports, we demonstrate a novel fluorescence-quenching mechanism attributable to the second-phase Eu₂W₂O₉ in non-equivalent substituted SrWO₄:xEu³⁺ phosphors. The crystal structure, elemental distribution, and luminescence properties of the as-prepared SrWO₄:xEu³⁺ phosphors are systematically investigated. A second-phase Eu₂W₂O₉ is confirmed when the Eu³⁺-doping concentration exceeds 20%, which produces the new structure defects and energy-transfer paths, resulting in fluorescence quenching in this material. This finding gives a new perspective to analyze the concentration-quenching mechanism of the non-equivalent substituted phosphors and can help in the design of new, efficient luminescence materials. In addition, the as-prepared SrWO₄:xEu³⁺ phosphors exhibit a strong intrinsic excitation in the range of 355-425 nm, which is accompanied by the Commission Internationale de I'Eclairage (CIE) coordinates at (0.653, 0.347) and stable color purity of up to 94.52%. A packaged white light-emitting diode with CIE chromaticity coordinates of (0.398, 0.335), correlated color temperature of 3132 K, and color rendering index of 84.3 is fabricated by SrWO₄:20%Eu³⁺ phosphors with blue BAM:Eu²⁺ and green YAGB:Tb³⁺ phosphors in a near-ultraviolet chip.