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Abstract: Luminescent properties of Pr3+ or Mn2+ singly doped and Pr3+, Mn2+ co-doped LaMgB5O10 are investigated by synchrotron radiation VUV light. When LaMgB5O10:Pr3+ is excited at185nm, the photon cascade emission between 4f levels of Pr3+ is observed. In the excitation spectra of LaMgB5O10:Mn2+ monitoring the 615nm emission of Mn2+, several excitation bands in a spectral range from 330 to 580nm are recorded, among which the most intense band is centered at 412nm (6A1g→4Eg–4A1g). This band has considerable spectra overlap with the 410nm emission (1S0→1I6) of Pr3+, which is favorable for energy transfer from Pr3+ to Mn2+. Such energy transfer is observed in the co-doped sample, converting the violet emission (410nm) of Pr3+ into the red emission (615nm) of Mn2+. The concentration dependence of transfer efficiency is also investigated. [Copyright &y& Elsevier]

Abstract: This report presents the luminescence properties of Ce3+ and Pr3+ activated Sr2Mg(BO3)2 under VUV–UV and X-ray excitation. The five excitation bands of crystal field split 5d states are observed at about 46729, 44643, 41667, 38314 and 29762cm−1 (i.e. 214, 224, 240, 261 and 336nm) for Ce3+ in the host lattice. The doublet Ce3+ 5d→4f emission bands were found at about 25840 and 24096cm−1 (387 and 415nm). The influence of doping concentration and temperature on the emission characteristics and the decay time of Ce3+ in Sr2Mg(BO3)2 were investigated. For Pr3+ doped samples, the lowest 5d excitation band was observed at about 42017cm−1 (238nm), a dominant band at around 35714cm−1 (280nm) and two shoulder bands were seen in the emission spectra. The excitation and emission spectra of Ce3+ and Pr3+ were compared and discussed. The X-ray excited luminescence studies show that the light yields are ∼3200±230 and ∼1400±100photons/MeV of absorbed X-ray energy for the samples Sr1.86Ce0.07Na0.07Mg(BO3)2 and Sr1.82Pr0.09Na0.09Mg(BO3)2 at RT, respectively. [ABSTRACT FROM AUTHOR]

Abstract: The intermediate role of Gd3+ in energy transfer to give light was investigated through spectroscopic study of Bi3+/Eu3+ doped YBO3/(Y,Gd)BO3 under VUV/UV excitation. All samples were prepared by solid-state reaction and the luminescent properties were characterized in a synchrotron radiation instrument. The results show that Gd3+ plays an intermediate “bridge” between the sensitizer of Bi3+ and the activator of Eu3+ in energy transfer in (Y,Gd)BO3:Bi3+,Eu3+ system. At the same, the mechanism for energy transfer was discussed, which is mainly through electric multipole interaction or exchange interaction. [Copyright &y& Elsevier]

Abstract: (Y0.99Bi0.01)BO3 phosphor was prepared and its luminescent properties were investigated using the synchrotron radiation instrument in this paper. Site-selective luminescence of Bi3+ in the YBO3 host was demonstrated by exciting/monitoring with different wavelengths at low temperature in this research. At the same time, the energy transfer between the centers of Bi3+ ions occupying different symmetric sites was observed. The excited energy levels of Bi3+ were identified through assigning the emission and excitation spectra. The paths and mechanism of energy transfer between the centers of Bi3+ occupying different symmetric sites were discussed finally. [Copyright &y& Elsevier]

Abstract: Phosphors CaYBO4:RE3+ (RE=Eu, Gd, Tb, Ce) were synthesized with the method of solid-state reaction at high temperature, and their vacuum ultraviolet (VUV)–visible luminescent properties in VUV–visible region were studied at 20K. In CaYBO4, it is confirmed that there are two types of lattice sites that can be substituted by rare-earth ions. The host excitation and emission peaks of undoped CaYBO4 are very weak, which locate at about 175 and 350–360nm, respectively. The existence of Gd3+ can efficiently enhance the utilization of host absorption energy and result in a strong emission line at 314nm. In CaYBO4, Eu3+ has typical red emission with the strongest peak at 610nm; Tb3+ shows characteristic green emission, of which the maximum emission peak is located at 542nm. The charge transfer band of CaYBO4:Eu3+ was observed at 228nm; the co-doping of Gd3+ and Eu3+ can obviously sensitize the red emission of Eu3+. The fluorescent spectra of CaYBO4:Ce3+ is very weak due to photoionization; the co-addition of Ce3+–Tb3+ can obviously quench the luminescence of Tb3+. [Copyright &y& Elsevier]

Abstract: VUV-Vis range spectroscopic characteristics from Pr3+ ions in CaMgAl14O23, LaF3, YBO3, YPO4 and LaF3 nanocrystals doped oxyfluoride glass ceramics are presented. Upon excitation into the 4f5d states, the emission spectra of Pr3+ correlated with the relative positions of the 1S0 state and the lowest 4f5d states. For Pr3+ ions in CaMgAl14O23 and LaF3, the lowest 4f5d state lies above the 1S0 state. So an efficient photon cascade emission occurred due to a two-step intraconfigurational 4f2→4f2 transition. For Pr3+ ions in YBO3 and YPO4, the lowest 4f5d state lies below the 1S0 state. The UV emission of 4f5d→4f2 transition was observed. Both types of Pr3+ ions exist in the oxyfluoride glass containing LaF3 nanocrystals. The positions of the lowest 4f5d state of Pr3+ in different host lattices are given. [Copyright &y& Elsevier]

Abstract: The energy transfer processes in Lu2SiO5:Ce3+ luminescence was investigated through the temperature dependent luminescence under excitation with VUV–UV. Ce1 center emission peaking at 393 and 422nm and Ce2 center emission peaking at 462nm were observed. Ce2 center emission is enhanced with the temperature, which can be explained by the rate of energy transfer from Ce1 center increases when the temperature rises. The Ce1 emission shows the thermal quenching effect under the direct excitation of Ce3+ at 262nm. However, under the interband excitation of 183nm, the Ce1 center emission exhibits undulating temperature dependence. This is because the emission is governed by thermal quenching and possible thermal enhancement of the transport of free carriers with the rising temperature. [Copyright &y& Elsevier]

Abstract: LiYF4, NaYF4, KYF4 and LiLuF4 doped with Pr3+ were synthesized by hydrothermal technique. Vacuum ultraviolet excitation and emission properties were investigated at 20K. A new type of photon cascade emission was observed in LiYF4:Pr3+ and LiLuF4:Pr3+, i.e. a first-step 4f5d→4f2 emission followed by a second 4f2→4f2 emission. In addition, the internal quantum efficiency of Pr3+ in NaYF4 and KYF4 within visible range was proved to be larger than unity using the branching ratios data corrected by the emission spectra of YF3:Pr3+. [Copyright &y& Elsevier]

Abstract: Crystal field interaction of the 5d electron [H CF(5d)] and the Coulomb interaction between the 5d and the 4f electrons [H C(fd)] are the most important interactions in determining the structure of the 4f5d configuration of Pr3+ in solids. Energy levels of the 4f5d configuration in YPO4:Pr were calculated by diagonalizing the simplified Hamiltonian H CF(5d)+H C(fd). Coulomb exchange interaction compresses the extension of the triplet states, while expands that of the singlet states. Thus, for the triplet states, H C(fd) could be considered approximately as a perturbation to H CF(5d). Since the ground state of the 4f 2 configuration is a triplet, the triplet state structure in the 4f5d configuration determines the spectroscopic properties of the ground state absorption. Absorption spectrum calculated by using the obtained 4f5d wave functions is comparable with the experimental ones. [Copyright &y& Elsevier]

Abstract: The luminescent properties of the undoped, the Eu2+ or Dy3+ singly doped as well as Eu2+ and Dy3+ codoped Sr2MgSi2O7, were investigated using synchrotron radiation and xenon or mercury lamp as excitation source. Under 172nm excitation, besides the emission band peaked at 465nm from Eu2+ in Sr2MgSi2O7:Eu2+, Dy3+, there are evident emission lines at 487 and 575nm from intraconfigurational 4f transitions of Dy3+. After the UV excitation, the peak temperatures of thermoluminescence curves were at ∼65°C for Sr2MgSi2O7:Eu2+ and ∼120°C for Sr2MgSi2O7: Dy3+. Afterglow emission spectra peaking at 465nm were increased with rising temperature from 180K to room temperature. The results show that the role of Eu2+ in Sr2MgSi2O7:Eu2+, Dy3+ is not only the luminescence center, but also a trap center. On the contrary, the role of Dy3+ ions can be not only as a trap center, but also as a luminescence center. [Copyright &y& Elsevier]