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We present novel near-infrared (NIR) Cr3+-doped non-gallate super-long-persistence phosphors (Zn1+xAl2-2xGexO4:Cr3+) by Germanium substitution in the original ZnAl2O4:Cr3+. Unlike the negligible NIR persistent luminescence of ZnAl2O4:Cr3+ upon UV or visible light excitation, the Ge substituted phosphors feature strong and super-long-persistent luminescence at approximately 650–750 nm for more than 120 h. The relation between the Ge substitution and the defect trapping states is investigated systematically. The experimental results combined with the first-principles calculations reveal that GeZn○○ and GeAl○ in the spinel structure would introduce shallow and deep defect states in the band gap to serve as new efficient traps, which are mainly responsible for the strong and super-long-persistent luminescence upon UV or visible light excitation. The present advanced phosphors is an alternative candidate for applications in biomedical imaging and night-vision surveillance.

Yb 3+ and Tb 3+ singly doped and Tb 3+ –Yb 3+ co-doped Ca 5 (BO 3 ) 3 F phosphors were prepared by a solid state reaction method. The luminescence emission and excitation spectra as well as the luminescence decay curves were investigated. The emission bands of Yb 3+ ion are located around 1000 nm, matching well with the optimal response of Si-based solar cells. Tb 3+ can be a sensitizer for Yb 3+ in the host. The energy transfer from Tb 3+ to Yb 3+ was investigated, the energy transfer mechanism was proposed as cooperative energy transfer. Tb 3+ concentration dependent quantum efficiency was calculated and the maximum efficiency approached 115.5%.

Near-infrared (NIR) quantum cutting (QC) from the Tm3+: 1G4 state essentially occurs via a three-step cascade radiation (case 1) and two-step cross-relaxations (case 2) by varying the Tm3+ content (x) from 0.0005 to 0.05 in La2–xTmxBaZnO5. In case 1, with the Tm3+ content x < 0.005, the energy of the 1G4 excited state is down-converted to three NIR photons emitted at approximately 1200, 1480, and 1800 nm, with 3H4 and 3F4 acting as intermediate levels, while in case 2, with the Tm3+ content x ≥ 0.005, the energy will be triply cut into approximately 1800 nm photon emissions. The three-photon NIR QC phenomena are investigated in terms of the static and dynamic photoluminescence. Based on the dependence of cross-relaxation and concentration quenching on Tm3+ density, a rate-equation model was built to describe the energy transfer (ET) dynamics of Tm3+. The calculation of internal quantum yield (QY) was developed by considering nonradiative processes, and the maximum QY for photon emission at 1800 nm was 198...

The BaCaBO3F wide band gap host and the charge-compensated phosphors BaCaBO3F:Ln3+ (Ln = Ce, Tb, Gd) and BaCaBO3F:Ce3+,Tb3+ have been synthesized by a solid-state reaction method at high temperature. Their spectroscopic properties in the vacuum ultraviolet (VUV)–vis range have been investigated. The band gap of the host lattice is estimated at 7.8 eV, which is considerably higher than the value found from its diffuse reflectance spectrum. The 5d crystal field level locations, Stokes shift, and Huang–Rhys factor have been determined from the VUV excitation and near-UV emission spectra of BaCaBO3F:Ce3+. The 5d1 decay lifetime is 29 ns at x ∼ 0.005. Concentration quenching occurs for Ba1–2xCexNaxCaBO3F with maximum intensity at x ∼ 0.035 and with critical distance Rc = 17.7 A. An unusual broad, intense band in the excitation spectrum of BaCaBO3F:Gd3+ is assigned to a near-defect exciton. Very weak emission from 5D3, and intense green emission from 5D4, has been assigned for BaCaBO3F:Tb3+. In the VUV region, ...

This report presents the luminescence properties of Ce 3+ and Pr 3+ activated Sr 2 Mg(BO 3 ) 2 under VUV–UV and X-ray excitation. The five excitation bands of crystal field split 5d states are observed at about 46 729, 44 643, 41 667, 38 314 and 29 762 cm −1 (i.e. 214, 224, 240, 261 and 336 nm) for Ce 3+ in the host lattice. The doublet Ce 3+ 5d→4f emission bands were found at about 25 840 and 24 096 cm −1 (387 and 415 nm). The influence of doping concentration and temperature on the emission characteristics and the decay time of Ce 3+ in Sr 2 Mg(BO 3 ) 2 were investigated. For Pr 3+ doped samples, the lowest 5d excitation band was observed at about 42017 cm −1 (238 nm), a dominant band at around 35714 cm −1 (280 nm) and two shoulder bands were seen in the emission spectra. The excitation and emission spectra of Ce 3+ and Pr 3+ were compared and discussed. The X-ray excited luminescence studies show that the light yields are ∼3200±230 and ∼1400±100 photons/MeV of absorbed X-ray energy for the samples Sr 1.86 Ce 0.07 Na 0.07 Mg(BO 3 ) 2 and Sr 1.82 Pr 0.09 Na 0.09 Mg(BO 3 ) 2 at RT, respectively.

A series of samples with nominal chemical formulas La 2-x Ce x CaB 10 O 19 and La 2 Ca 1-2x Ce x Na x B 10 O 19 were prepared by a solid state reaction route at high temperature. Their luminescence properties were investigated by the steady state excitation and emission spectra in the VUV-vis range, the luminescence decays, and the time-resolved emission spectra (TRES). The results demonstrate that Ce 3+ ions occupy two lattice sites in all samples. The lowest 5d absorption bands for two sites are at about 272 (La 3+ site) and 312 nm (Ca 2+ site), respectively. The emission for Ce 3+ in the La 3+ site shows a shorter decay time of 12 ns, and the doublet emission bands have maxima at about 291 and 310 nm. The emission for the Ce 3+ in Ca 2+ site has a longer lifetime of 26 ns with band maxima at about 329 and 355 nm. Efficient energy transfer between both sites occurs in the samples.

A series of phosphors Ca3La3(1-x)Tb3x(BO3)5 were synthesized by using a high-temperature solid-state reaction technique, and their VUV-vis luminescence properties were investigated. Strong host-related absorption is observed in the VUV region, and the f–d transitions of Tb3+ in the host lattice are assigned and discussed. The influence of both the doping concentration and the temperature on the spectroscopic properties that include the relative emission intensity and the decay time is investigated.

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.

The spectroscopic properties of Ce 3+ , Pr 3+ and Tb 3+ activated SrB 4 O 7 in VUV–vis range were investigated. The split 5d levels for Ce 3+ 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 Pr 3+ doped SrB 4 O 7 , 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 Ln 3+ (Ln = Ce, Pr, Tb) ions in SrB 4 O 7 is proposed.

Fluoro-apatite M5(PO4)3 F( M= Ca, Sr, Ba) phosphors activated with Ce 3+ ions were prepared by a solid state reaction technique at high temperature. The excitation spectra in the VUV (vacuum ultraviolet)–UV range and the emission spectra in the UV–vis range together with decay time spectra are investigated and discussed. X-ray excited emission spectra were measured and light yields are calculated. The results revealed that Ca(II) sites are preferentially occupied at low doping concentration, and then Ca(I) sites are dominant with the increasing of concentration for Ce 3+ in Ca5(PO4)3F. In contrast, Ce 3+ ions mainly occupied the Sr(II)/Ba(II) sites in Sr5(PO4)3 Fa nd Ba5(PO4)3F even at higher doping concentration. The low light output seems to suggest that the materials are not suitable x-ray or gamma-ray phosphors. (Some figures in this article are in colour only in the electronic version)

The phosphors NaGdFPO{sub 4}:Ln {sup 3+} and GdPO{sub 4}:Ln {sup 3+} (for Ln{sup 3+}=Ce{sup 3+} and Tb{sup 3+}) were prepared by solid-state reaction technique, the VUV-vis spectroscopic properties of the phosphors were investigated, and we vividly compare the luminescence of Ce{sup 3+} and Tb{sup 3+} in the hosts. For phosphors GdPO{sub 4}:Ln {sup 3+}, the band near 155 nm in VUV excitation spectrum is assumed to be the host-related absorption, and for NaGdFPO{sub 4}:Ln {sup 3+} the absorption is moved to longer wavelength, near 170 nm, showing the P-O bond covalency increased after fluoridation. The f-d transitions of Ce{sup 3+} and Tb{sup 3+} in the host lattices are assigned and corroborated, and it was found that the 5d states are with lower energy in NaGdFPO{sub 4}:Ln {sup 3+} than those in GdPO{sub 4}:Ln {sup 3+}. For fluoridation of GdPO{sub 4}:Ln {sup 3+} to NaGdFPO{sub 4}:Ln {sup 3+}, the energy change of Ln {sup 3+} (Ln=Ce, Tb) 5d states is consistent with that of host-related absorption.

The spectroscopic properties of Ba2Mg(BO3)2:Ce3+ and Ba2Mg(BO3)2:Eu2+ in vacuum-ultraviolet-vis range were investigated. The 5d crystal-field splitting components and the barycenter of Ce3+, the lowest 5d levels, the emission and the Stokes shifts of Eu2+ and Ce3+ in the host lattices, as well as the host-related absorption are identified and discussed in terms of the crystal structure of the host lattice.

In order to develop a suitable green phosphor for plasma display panels (PDPs), samples Ca 5-2x Tb x Na x (PO 4 ) 3 F for x = 0.20, 0.35, 0.50, 0.65, 0.80, and 0.95 were prepared by a solid-state reaction technique at high temperature. The vacuum ultraviolet (VUV, wavelength λ 50,000 cm -1 )-vis spectroscopic properties and decay characteristic were investigated. Because the phosphor Ca 5-2x Tb x Na x (PO 4 ) 3 F for x = 0.95 shows broad and strong absorption in the vacuum ultraviolet (VUV) range, exhibits higher intensive emission under 147/172 nm excitation, and has a shorter decay time (τ ∼ 2.19 ms) in comparison with the commercial green PDP phosphor Zn 2 SiO 4 /Mn 2+ , it is considered to be a promising green phosphor in PDPs.

Strong tunable photoluminescence (PL) from silicon oxynitride materials have been demonstrated by modulating the oxygen content. The increase of oxygen content in the films from 8% to 61% results in red, orange-yellow and white switching PL. The change in PL characteristics of these films is ascribed to the variation of defect luminescent centers as well as the evolution of dominant phase structures changing from silicon nitride to silicon oxynitride and silicon oxide. The intense PL intensity is suggested from the nanoseconds recombination lifetime as well as the alleviation of internal stress in silicon oxynitride.

Eu(3+)-activated La2CaB10O19 phosphors with nominal chemical formulae La(2-x)Eu(x)CaB10O19 and La2Ca(1-2x)Eu(x)Na(x)B10O19 were prepared. The luminescence properties under VUV-UV excitation were investigated. Luminescence spectra reveal Eu(3+) ions occupy both Ca(2+) and La(3+) sites in all samples. The O(2-)→ Eu(3+) charge transfer bands (CTBs) and the (5)D0→(7)F0 emissions of Eu(3+) at Ca (2+) site and La(3+) site are identified, respectively. The schematic energy levels for Eu(3+) in two sites were achieved. Luminescence decays of the (5)D0→(7)F0 transitions were measured for both sites.

The luminescence properties of Ce3+ activated Ba2Ca(BO3)2 with K+ as a charge compensator have been investigated and compared with those with Na+-compensating. Energy transfer of Ce3+ in Ba2+ (i.e. Ce(1)3+) and Ca2+ (i.e. Ce(2)3+) sites has been proven by VUV–UV excitation and emission spectra, luminescence decays and time-resolved emission spectra. In addition, by combining Ba2Ca(BO3)2 : Ce3+ phosphors with near-ultraviolet (n-UV) InGaN chips, the fabricated light-emitting diodes (LEDs) show intense bluish-green emission, and the phosphors exhibit good thermal stability.

The phosphors Ba3Gd(BO3)3:Ce3+ were prepared by a solid-state reaction technique at high temperature. The vacuum ultraviolet-ultraviolet and visible spectroscopic properties of the phosphors together with decay time curves are investigated and discussed. The spectroscopic properties are explained by occupancy of Ce3+ at two different Gd sites in the host lattice. The x-ray excited emission spectra of Ba3Gd(BO3)3:Ce3+ were studied and the number of photons emitted per unit of absorbed x-ray energy was calculated. The yield is rather poor and Ba3Gd(BO3)3:Ce3+ appears not a suitable x-ray phosphor.

In order to develop a suitable green phosphor for plasma display panels (PDPs), samples Ca 5-2x Tb x Na x (PO 4 ) 3 F for x = 0.20, 0.35, 0.50, 0.65, 0.80, and 0.95 were prepared by a solid-state reaction technique at high temperature. The vacuum ultraviolet (VUV, wavelength λ 50,000 cm -1 )-vis spectroscopic properties and decay characteristic were investigated. Because the phosphor Ca 5-2x Tb x Na x (PO 4 ) 3 F for x = 0.95 shows broad and strong absorption in the vacuum ultraviolet (VUV) range, exhibits higher intensive emission under 147/172 nm excitation, and has a shorter decay time (τ ∼ 2.19 ms) in comparison with the commercial green PDP phosphor Zn 2 SiO 4 /Mn 2+ , it is considered to be a promising green phosphor in PDPs.