Ca₄Nb₂O₉: Sm³⁺ Research on the Luminescent Properties of Orange Red Fluorescent Powder

Highly efficient and thermally stable orange-red phosphors are critical for optimizing the color quality of phosphor-converted white LEDs. Here, Ca_4-1.5xNb₂O₉: xSm³⁺ were fabricated via a conventional solid-state route. Structural characterization confirms that all samples crystallize in a single-phase monoclinic lattice, where Sm³⁺ is successfully incorporated into Ca²⁺ sites, inducing slight lattice contraction without destroying the host framework. Spectroscopic analyses reveal that aliovalent substitution generates localized defect states and narrows the bandgap from 3.67 to 3.44 eV, thereby enhancing optical absorption. Under 406 nm excitation, the materials display intense Sm³⁺-centered emissions dominated by the ⁴G_5/2 → ⁶H_7/2 transition, yielding saturated orange-red output. The optimal composition (x = 0.03) achieves maximum luminescence, while concentration quenching is attributed to dipole-dipole interactions. In addition, the phosphor exhibits saturated orange-red emission with chromaticity coordinates of (0.5964, 0.4013), highlighting its strong color performance. Overall, the results demonstrate that Ca_4-1.5xNb₂O₉: xSm³⁺ is a promising candidate for high-performance WLEDs.