Synthesis, characterization and optical properties of LiSm(PO3)4 phosphor

The phosphor LiSm(PO3)4 has been prepared by the solid state reaction and characterized using the techniques XRD, IR and Raman spectroscopies. The optical properties of the Sm3+ ions in this compound have been investigated in detail based on the diffuse reflectance, the excitation, the emission spectra and the photoluminescence decay time. The optical band gap energy of the studied phosphor (Eg ≈ 4.22 eV) has been calculated from the diffuse reflectance by using the Kubelka-Munk function and Tauc's relation. The excitation spectrum shows four photoluminescence bands at 560, 600, 650 and 700 nm corresponding to the 4G5/2 → 6HJ (J = 5/2, 7/2, 9/2 and 11/2) electronic transitions of the Sm3+ ion, respectively. The decay time is a pure radiative transition and the lifetime value for the transition 4G5/2 → 6H7/2 is found equal to 32.5 μs. The effects of the crystal structure and Li+ on the lifetime have been revealed. The CIE chromaticity coordinates reveal that this phosphor can be a promising orange-reddish luminophore for application in LED.