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, Ca4-1.5xNb2O9: 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 4G5/2 → 6H7/2 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 Ca4-1.5xNb2O9: xSm3+ is a promising candidate for high-performance WLEDs.