Vacuum ultraviolet and near-infrared excited luminescence properties of Ca3(PO4)2:RE3+, Na+ (RE=Tb, Yb, Er, Tm, and Ho)

Tb3+, Yb3+, Tm3+, Er3+, and Ho3+ doped Ca3(PO4)2 were synthesized by solid-state reaction, and their luminescence properties were studied by spectra techniques. Tb3+-doped samples can exhibit intense green emission under VUV excitation, and the brightness for the optimal Tb3+ content is comparable with that of the commercial Zn2SiO4:Mn2+ green phosphor. Under near-infrared laser excitation, the upconversion luminescence spectra of Yb3+, Tm3+, Er3+, and Ho3+ doped samples demonstrate that the red, green, and blue tricolored fluorescence could be obtained by codoping Yb3+-Ho3+, Yb3+-Er3+, and Yb3+-Tm3+ in Ca3(PO4)2, respectively. Good white upconversion emission with CIE chromaticity coordinates (0.358, 0.362) is achieved by quadri-doping Yb3+-Tm3+-Er3+-Ho3+ in Ca3(PO4)2, in which the cross-relaxation process between Er3+ and Tm3+, producing the 1D2-3F4 transition of Tm3+, is found. The upconversion mechanisms are elucidated through the laser power dependence of the upconverted emissions and the energy level diagrams. - Graphical abstract: The CPO:0.25Tb3+, 0.25Na+ exhibits a comparable brightness to the commercial Zn2SiO4:Mn2+ upon 147 nm excitation. Good white light color is achieved in CPO:Yb3+-Tm3+-Er3+-Ho3+ under 980 nm excitation. Highlights: → Ca3(PO4)2:Tb3+,Na+ exhibits a comparable brightness with commercial Zn2SiO4:Mn2+. → Red, green and blue colors are achieved in Yb3+, Ho3+, Er3+, Tm3+ doped Ca3(PO4)2. → Good white emission is obtained in Yb3+-Ho3+-Er3+-Tm3+ quadri-doped Ca3(PO4)2. → Ca3(PO4)2:Tb3+, Yb3+, Ho3+, Er3+, Tm3+ could be potential phosphors.