Vacuum ultraviolet and near-infrared excited luminescence properties of Ca 3(PO 4) 2: RE3+, Na + ( RE=Tb, Yb, Er, Tm, and Ho)

Abstract

Tb 3+, Yb 3+, Tm 3+, Er 3+, and Ho 3+ doped Ca 3(PO 4) 2 were synthesized by solid-state reaction, and their luminescence properties were studied by spectra techniques. Tb 3+-doped samples can exhibit intense green emission under VUV excitation, and the brightness for the optimal Tb 3+ content is comparable with that of the commercial Zn 2SiO 4:Mn 2+ green phosphor. Under near-infrared laser excitation, the upconversion luminescence spectra of Yb 3+, Tm 3+, Er 3+, and Ho 3+ doped samples demonstrate that the red, green, and blue tricolored fluorescence could be obtained by codoping Yb 3+–Ho 3+, Yb 3+–Er 3+, and Yb 3+–Tm 3+ in Ca 3(PO 4) 2, respectively. Good white upconversion emission with CIE chromaticity coordinates (0.358, 0.362) is achieved by quadri-doping Yb 3+–Tm 3+–Er 3+–Ho 3+ in Ca 3(PO 4) 2, in which the cross-relaxation process between Er 3+ and Tm 3+, producing the 1 D 2– 3 F 4 transition of Tm 3+, is found. The upconversion mechanisms are elucidated through the laser power dependence of the upconverted emissions and the energy level diagrams.