Synthesis, structural and luminescence studies of LiSrVO₄:Sm³⁺ nanophosphor to fill amber gap in LEDs under n-UV excitation

The LiSr_(1−3/2x) VO₄:xSm³⁺ (0.0025 ≤ x ≤ 0.03) phosphors were prepared by the low cost combustion method. The structural and luminescence studies were carried out with powder X-ray diffraction, transmission electron microscopy, photoluminescence spectroscopy and diffuse reflectance spectroscopy (DRS) characterization techniques. The nanosized phosphor crystallized into the pure monoclinic phase with space group P2/m. The optimized LiSr_0.9775VO₄:0.015Sm³⁺ phosphor displayed orange-red emission in the range of 500−750 nm with a maximum peak at 600 nm upon excitation with 317 and 401 nm. The emission spectra have four sharp peaks attributed to the ⁴G_5/2 to ⁶H _J (J = 5/2, 7/2, 9/2, 11/2) transitions of Sm³⁺. The emission has CIE chromaticity coordinates at (0.59, 0.41). The type of energy transfer between the Sm³⁺ ions responsible for concentration quenching was confirmed to be electric dipole–dipole interaction as determined with the Van Uitert model. The band gap and Urbach energy of a typical LiSr_0.9775VO₄:0.015:Sm³⁺ phosphor sample, using DRS studies, ware estimated to be 3.65 eV and 165.5 meV. The results indicated that the LiSrVO₄:Sm³⁺ is a potential amber gap phosphor to be excited by n-UV LED chips for applications in lighting and LED displays.