Emission Enhancement of Eu3+ Ions in LiY(PO3)4 Phosphate Phosphors via Anionic SO4 2− Substitution

Abstract

Eu3+-doped LiY(PO3)4(1-x)(SO4)4x (LYSO:Eu) phosphors are synthesized by high-temperature solid-phase method. The crystal structure, microscopic morphology and photo-spectrographic characteristics are analyzed respectively. The phosphor exhibits the strongest excitation peak at 397 nm, which indicates that the sample can be effectively excited by the near-ultraviolet/ultraviolet LED chip. The characteristic emission peaks of Eu3+ ion 5D0→7FJ (J = 0, 1, 2, 3, 4) are observed from the PL spectrum, and the orange emission peak originating from the magnetic dipole transition 5D0→7F1 of Eu3+ is located near 597 nm. When the SO4 2− concentration exceeds 22.5 mol%, the quenching of the phosphor occurs. The Eu3+ emission still retains 78.8% of the initial strength at 495 K, with excellent thermal stability. The emission intensity is decreased with the increase of SO4 2− concentration, indicating that the SO4 2− co-doping leads to an increase in the probability of non-radiative transitions. The best quantum efficiency of the LiY0.95(PO3)2.6(SO4)1.4: 0.05Eu3+ sample is 86.65%, and the CIE chromaticity coordinates of this sample are (0.653, 0.347), which are close to the international standard red color coordinates (0.67, 0.33). These results indicate that LYSO:Eu has a good application in NUV/UV excited white LEDs. Influence of anionic substitutions of SO4 2− on the optical properties is discussed.