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

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.