Microstructure and photoluminescence of Eu-doped NiMoO₄ phosphors

In this study, Eu³⁺-activated α-NiMoO₄ red phosphors were synthesized through a mass-producible solid-state reaction for potential applications in white light-emitting diodes aimed at next-generation lighting solutions. The structural, morphological, and photoluminescence properties of α-NiMoO₄:Eu³⁺ phosphors were systematically investigated as a function of Eu³⁺ concentration and calcination temperature. Compared to Ni sites, substituting Eu at Mo sites led to the formation of a higher proportion of secondary phases, which resulted in reduced luminescence intensity. Consequently, our investigation focused on the synthesis of Ni_1-xEu_xMoO₄ phosphors, where Eu³⁺ doping up to 5 at.% yielded a single-phase material, whereas higher doping levels promoted the formation of secondary phases. As the doping concentration increased, the PL intensity initially increased, reaching a maximum at 20 at.% Eu³⁺ content, and subsequently declined due to concentration quenching effects. The Ni_0.8Eu_0.2MoO₄ powders calcined at 1100 °C demonstrated excellent thermal stability, maintaining approximately 75.2 % of their initial PL intensity at 200 °C. These results highlight that α-NiMoO₄:Eu³⁺ phosphors, synthesized through a simple and industrially scalable method, are promising candidates for high-performance, thermally stable red-emitting materials, well-suited for solid-state lighting and other optoelectronic applications.