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

Abstract

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 LiSr0.9775VO4:0.015Sm3+ 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 4G5/2 to 6HJ (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 LiSr0.9775VO4:0.015: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.