NaSrVO₄:Sm³⁺ - An n-UV convertible phosphor to fill the quantum efficiency gap for LED applications

The structural and luminescent properties of Sm³⁺ doped NaSrVO₄ phosphors prepared by the combustion method were investigated. The phosphors were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence spectroscopy (PL) and diffuse reflectance spectroscopy (DRS). NaSrVO₄ crystallized into the monoclinic phase with P2_1/n space group. The Debye Scherrer's formula and Williamson-Hall (W-H) plot were used to determine the average crystallite size of the phosphors. Upon near-UV excitation, the phosphor gives the characteristic orange-red emission ascribed to the intra-4f-shell ⁴G_5/2 to ⁶H_J (J=5/2, 7/2, 9/2, 11/2) transitions of Sm³⁺. The diffused reflectance spectra of the phosphors were used to calculate the optical band gap (E_g) of the material, which was estimated to be 3.58 eV. The chromaticity coordinates (x=0.61, y=0.39) of the phosphors further validated the orange-red emission of the material. This phosphor may be used as near ultraviolet (n-UV) convertible orange-red emitting phosphor in light emitting diodes (LEDs).