Photoluminescence control and abnormal Eu orange emission in Ln (Ln = Ce, Eu)-doped oxyapatite-type phosphors

Establishing effective methods to optimize luminescent materials has been a significant challenge for white light-emitting-diode (WLED) applications. Herein, we successfully realized the adjustment of the photoluminescence and enhancement of the thermal stability of Ln 3+ (Ln 3+ = Ce 3+ , Eu 3+ )-doped Ca 10− x / y Ba x / y (PO 4 ) 6 O phosphors. First, Ba 2+ ions from raw BaCO 3 material realized a spectral red shift from 464 nm to 506 nm, which we suggested to be due to a synergistic effect from a centroid shift and crystal field splitting. When using BaHPO 4 as a raw material, the PL intensity was 6.5 times that of the initial intensity. Surprisingly, the thermal stability was also improved, which was attributed to the increasing lattice distortion introducing many traps. Second, the Ca 10 (PO 4 ) 6 O:Eu 3+ red phosphor exhibited an abnormal emission phenomenon involving the 5 D 0 → 7 F 0 peak at 575 nm becoming the strongest emission peak and the 5 D 0 → 7 F 1 peak at 585 nm becoming particularly weak. The site symmetry and charge transfer states were speculated to be closely related to this phenomenon. The charge transfer states were not only correlated with the crystal field strength, but also related to f-electron delocalization, which significantly influenced the energy-level structure of Eu 3+ . More importantly, according to the relationship between the I ( 5 D 0 → 7 F 0 )/ I ( 5 D 0 → 7 F 1 ) ratio and the lattice structure, Eu 3+ in the Ca 10 (PO 4 ) 6 O compound could be applied as a probe to explore the matrix information, which would provide a helpful method to investigate the lattice structures of compounds and also guide researchers to design new suitable red phosphors. Controllable photoluminescence adjustment of Ce 3+ /Eu 3+ -doped phosphors.