Synthesis and luminescence properties of oxyapatite-type ZnLa4(SiO4)3O:Eu3+ phosphor for high CRI w-LEDs, latent fingerprints, and security ink

The Eu3+-doped oxyapatite-type ZnLa4(SiO4)3O (ZLSO) phosphors with a strong red emission were successfully synthesized. The pure phase of the phosphors with the hexagonal system was verified through X-ray diffraction. The band gap energy of the ZLSO was calculated using Materials Studio and measured using the diffuse reflection spectra. Attributed to the 7F0→5L6 transition of Eu3+ at 394 nm, the prepared phosphors showed a more intense emission at 614 nm than at 590 nm, due to their asymmetric position. The optimized doping concentration of the ZLSO:xEu3+ sample was 20 mol%, and the relevant mechanism of concentration quenching was dipole-quadrupole interaction. Notably, the ZLSO:Eu3+ phosphors exhibited preferable thermal stability, with an activation energy of 0.289 eV. The fabricated warm white light-emitting diodes (w-LEDs) with ZLSO:Eu3+ phosphors presented a high average colour rendering index (Ra = 95, CCT = 5233 K). Meanwhile, the level 1–3 structures of latent fingerprints (LFPs) were distinctly displayed by ZLSO:Eu3+ samples, and security ink was successfully used to encrypt information. In summary, the highly efficient oxyapatite-type ZLSO:20 mol%Eu3+ phosphors have attractive application potential in multiple application fields, such as w-LEDs, LFPs, and security ink.