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Phosphors of Eu activated BaMg(BO) were prepared by a high-temperature solid-state reaction technique. The phase purity was characterized by powder X-ray diffraction (XRD). The luminescence properties in the VUV-vis range as well as the decay curves have been investigated. The results demonstrate that the band near 176 nm in the VUV excitation spectra can be ascribed to host-related absorption. The charge-transfer bands (CTBs) of O → Eu in BaMg(BO):Eu are at about 231 nm. The emission intensity of the D→F transition (594 nm) is dominant upon excitations at 172 nm or 231 nm (CTB), while that of D→F transition (613 nm) is dominant when excitations are at 395 nm (the F→L transition of Eu) or at other f-f transitions. [ABSTRACT FROM AUTHOR]

The phosphors, fluorapatites M5(PO4)3F (M=Ca, Sr, Ba) activated with Dy3+ ions, were prepared by a high-temperature solid-state reaction technique. The VUV-UV excitation spectra and emission spectra under VUV/UV excitation were measured. The phosphors show broad and strong absorption near 172 nm and intensive emission with the chromaticity coordinates entering the white light region. Hence, the phosphors may be considered as suitable candidates for Hg-free lamps. [ABSTRACT FROM AUTHOR]

This paper presents temperature dependence of emission spectra (290 nm and 340 nm bands), excitation spectra (250-3000 Å), luminescence decay time as well as their excitation effect for CeF[sub 3] crystals. The results indicate that energy transfer from Ce[sup 3+] to defect centers in the CeF[sub 3] crystals was very efficient as temperature increased. The 340 nm emission band may originate from some defects near Ce[sup 3+], rather than Ce[sup 3+] perturbed defects. [ABSTRACT FROM AUTHOR]

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: Luminescence properties of LSO:Ce, including the excitation spectra in 130–370nm and the emission spectra in 350–500nm as well as decay times were studied by synchrotron radiation at different temperature between 79 and 295K. The temperature dependence of the VUV (178nm) excitation band was different from that of the UV (264, 296 and 364nm) ones of LSO:Ce luminescence (436nm). The former had no thermo-quenching and the latter thermo-quenching was evident for both single crystal and powder sample. Not only the excitation spectra, but also the VUV excited emission spectra showed a temperature dependent behavior. The difference can be ascribed to a different energy transfer process in the LSO:Ce material under VUV and UV excitation. When the temperature rises from 79 to 295K, the VUV excited luminescence decay times vary in the range of 27.6–32.4ns for single crystal and from 29.8 to 25.5ns for powder sample. [Copyright &y& Elsevier]

Abstract: The spectroscopic properties of Na3Gd(PO4)2 and Na3Gd(PO4)2:Ce3+ phosphors in the VUV–UV spectral range were investigated. Five excitation bands of Ce3+ ions at Gd3+ sites are observed at wavelengths of 205, 246, 260, 292, and 321nm. Doublet Ce3+ 5d→4f emission bands are observed at 341 and 365nm with a decay constant τ 1/ e around 26ns. The X-ray excited luminescence of Na3Gd0.99Ce0.01(PO4)2 at room temperature shows a photon yield of ∼17,000photons/MeV of absorbed X-ray energy. [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: The stilbene-3 doped lead–tin–fluorophosphate glasses were successfully prepared and the luminescence spectra obtained from VUV–UV synchrotron radiation were investigated. The emission peaked about 440nm from the undoped glass is observed at low temperature but quenches at room temperature. The doped glass exhibits strong characteristic emission of stilbenen-3 with 467 and 436nm Gaussian bands under ultraviolet 250–330nm excitation (characteristic excitation of stilbene-3) but weak emission under vacuum ultraviolet 190nm excitation (host excitation). It is suggested that the energy transfer from host to the stilbene-3 dye can occur but the efficiency is still fairly low. [Copyright &y& Elsevier]

Abstract: The luminescent properties of GdTaO4 and GdTaO4:Eu3+ were investigated using synchrotron radiation VUV–UV source. Broad-band emissions peaked at 384 and 468 nm due to the TaO4 group and 6P J →8S7/2 emission of Gd3+ at 316 nm under the UV excitation are found at 20 K, but quenched at room temperature. The excitation spectra of GdTaO4:Eu3+ monitoring the 5D0→7F2 emission of Eu3+ comprise interband excitation of host, the TaO4 group excitation, the CTS of Eu3+–O2− and Gd3+ 8S7/2→6I J transitions. The energy-transfer processes among these centers are analyzed from the luminescence spectra. Under the VUV–UV excitation, GdTaO4:Eu3+ shows a series of emission lines ascribed to the 5D J →7F J transitions. The energy levels of Eu3+ in the GaTaO4 host were tentatively assigned according to the emission spectra. [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 spectroscopic properties of Ce3+, Pr3+ and Tb3+ activated SrB4O7 in VUV–vis range were investigated. The split 5d levels for Ce3+ in the host lattice are discussed and an environmental factor F c is used to explain the crystal field splitting (CFS). The photon cascade emission (PCE) process was observed in Pr3+ doped SrB4O7, and the quantum efficiency of PCE is estimated. An empirical relationship between the lowest spin-allowed f–d transition energy [W fd(n)] and n-value for 4f n -series Ln3+ (Ln=Ce, Pr, Tb) ions in SrB4O7 is proposed. [Copyright &y& Elsevier]

Abstract: Photoluminescence spectrum of Ce:YAG single crystal was studied employing vacuum ultraviolet (VUV) synchrotron radiation. Intrinsic absorption edge at about 52,000cm−1 was observed in the absorption spectrum. From the VUV excitation spectrum, the energy of the highest d-component of 53,191cm−1 (188nm) for the Ce3+ ions in YAG was obtained at 300K. The disappearance of the third 5d level at 37,735cm−1 (265nm) in absorption and excitation spectra in our samples may be due to the impurity Fe3+ ions absorption. [Copyright &y& Elsevier]

Abstract: The phosphors NaGdFPO4:Ln 3+ and GdPO4:Ln 3+ (for Ln3+=Ce3+ and Tb3+) were prepared by solid-state reaction technique, the VUV–vis spectroscopic properties of the phosphors were investigated, and we vividly compare the luminescence of Ce3+ and Tb3+ in the hosts. For phosphors GdPO4:Ln 3+, the band near 155nm in VUV excitation spectrum is assumed to be the host-related absorption, and for NaGdFPO4:Ln 3+ the absorption is moved to longer wavelength, near 170nm, showing the P–O bond covalency increased after fluoridation. The f–d transitions of Ce3+ and Tb3+ in the host lattices are assigned and corroborated, and it was found that the 5d states are with lower energy in NaGdFPO4:Ln 3+ than those in GdPO4:Ln 3+. For fluoridation of GdPO4:Ln 3+ to NaGdFPO4:Ln 3+, the energy change of Ln 3+ (Ln=Ce, Tb) 5d states is consistent with that of host-related absorption. [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: The luminescence spectra of PbFCl single crystal under the excitation of synchrotron radiation vacuum ultraviolet–ultra violet (VUV–UV) were investigated. The emission spectra of PbFCl single crystal show a broad violet band peaking at 400nm having decreasing intensity with the rising temperature being from 20 to 293K under the excitation of VUV–UV. A weak ultraviolet band peaking at 325nm, which can be ascribed to the cation exciton emission of Pb2+, appears at 20K under the excitation at wavelength shorter than 247nm, but is completely quenched above 60K. The violet band emission due to energy transfer from cation exciton was observed, which became more effective above 60K. The luminescence in the violet band may be due to STE luminescence or is probably associated with the Pb2+ ion close to the Schottky-like defect. [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]