RbLn2F7 （Ln=Gd, Y, Er, Yb and Lu）, crystallized in the hexagonal RbEr2F7 structure type, is synthesized by a hydrothermal method. The excitation spectra of Eu 3+ -doped RbGd（Y）2F7 suggest that the oxygen content is very low in the samples obtained by hydrothermal synthesis. Only the f-f transitions of Gd 3+ ions are observed in the excitation spectrum of RbGd2F7∶Eu 3+ （0.5mol%）, while those of Eu 3+ ions do not appear. When the Gd 3+ ions are excited, the absorbed energy is transferred efficiently from Gd 3+ to Eu3+ . The spectra show that the doped Eu 3+ ions are located in non-centrosymmetric sites in hexagonal RbLn2F7.
The vacuum ultraviolet (VUV) luminescent properties of Pr3+-activated LaB3O6 were investigated with high-energetic synchrotron radiation from 20 to 300 K. In the emission spectra, the parity-forbidden 4f2→4f2 and parity-allowed 4f5d→4f2 transitions were observed simultaneously. In addition, it was also observed that the intensity of 4f5d→4f2 emission bands increased relative to the intensity of 4f2→4f2 emissions with increasing temperature. The thermal equilibrium model of energy levels was employed with respect to the lowest 4f5d state and 1S0 state of LaB3O6∶Pr3+, as a result of which the fitted curve had a good agreement with the experiment values, which clarified the physical nature of temperature-dependent emission characteristics of Pr3+ in LaB3O6.
The vacuum ultraviolet (VUV) spectroscopic properties of praseodymium (Pr3+, 1at%) doped LaF3 nanocrystals/glass at room temperature and 20 K are reported. Two types of Pr3+ ions, those in LaF3 nanocrystals and those in the glass host, were excited to 4f 5d band by VUV using synchrotron radiation as an excitation source, and emissions of 1S0 → 1D2 (336 nm), 1S0 → 1I6 (397 nm ) of Pr3+ in the nanocrystals and emissions of 4f 5d → 3HJ, 3FJ of Pr3+ in the glass appeared at the same time. But unlike in the bulk sample crystals, emission of 3P0 → 3HJ, 3FJ as the second step of the quantum splitting (QS) of Pr3+ in the LaF3 nanocrystals was not observed at room temperature, which could be explained that Pr3+ ions in the glass absorbed the energy of 3P0 → 3H4 of Pr3+ in the nanocrystals. Two types of excitation spectra monitoring different emissions were also measured, so it could be observed that the lowest energy of 4f 5d band of Pr3+ in the nanocrystals was about 53 500 cm-1 (186 nm) and in the glass about 33 800 cm-1(295 nm), respectively. These emission and excitation spectra were contrasted to those of bulk sample crystals LaF3∶Pr3+.
