Investigations on energy transfer mechanism and tunable luminescent properties of Co-doped Ca₉La(PO₄)₇:Dy³⁺,Eu³⁺ phosphors

Abstract

The synthesized Ca₉La(PO₄)₇:Dy³⁺,Eu³⁺(CLPO:Dy³⁺,Eu³⁺) phosphors were analyzed by phase structure, optical performance, thermal stability and lifetime. The XRD pattern indicated that both the matrix and rare earth ion-doped phosphors were pure phases, and the crystal structure was confirmed as trigonal system. Upon 351 nm excitation, Dy³⁺-doped CLPO phosphors performed two strong emission peaks at 481 nm and 573 nm. The energy transfer phenomenon from Dy³⁺ to Eu³⁺ can be found in the Dy³⁺, Eu³⁺ co-doped CLPO phosphors, and the color was tuned from red to blue upon 395 nm excitation with Eu³⁺ concentration decreasing. The energy transfer characteristic was evidenced by the excitation spectra, emission spectrum and decay time of the synthesized phosphors, and the mechanism of energy transfer from Dy³⁺ to Eu³⁺ was evaluated as a dipole–quadrupole interaction. In addition, temperature-dependent spectra were performed and the activation energy was further evaluated about 0.1902 eV. The results indicate the potential application of CLPO:Dy³⁺,Eu³⁺ phosphors in white LEDs.