4f Luminescence Research Articles

The First Example of Near-Infrared 4f Luminescence of Sandwich-Type Lanthanide Phthalocyaninates

The First Example of Near-Infrared 4f Luminescence of Sandwich-Type Lanthanide Phthalocyaninates

Growth of Ce-doped Ba3Gd(BO3)3 and Sr3Gd(BO3)3 single crystals by micro-pulling-down method and analysis of luminescence properties

Ce-doped double borates Ba3Gd(BO3)3 and Sr3Gd(BO3)3 (Ce:BGB and Ce:SGB, respectively) were grown by the micro-pulling-down method, and the luminescence properties of the crystals were investigated and compared with those of Ce-doped H-Ba3Y(BO3)3(Ce:H-BYB) crystals grown by the same method. Transmittance measurements showed the wavelength of absorption band was around 380nm for all the samples. Emission bands corresponding to the 5d→4f transition of Ce3+ were observed at around 425nm for Ce:BGB and Ce:SGB and at 435nm for Ce:H-BYB. The photoluminescence decay times of Ce:BGB, Ce:SGB, and Ce:BYB were 29.5ns, 35.2ns, and 26.8ns, respectively. The emission spectra obtained by excitation of 241Am (an α-emitter) revealed that the host luminescence was dominant (at around 315nm) in BGB and SGB and that a very low-intensity Ce3+ 5d→4f luminescence peak appeared at around 430nm. The relative light yield strength observed under 241Am excitation was corresponding to <100 and ∼270 photons/neutron for Ce:BGB and Ce:SGB, respectively, and these values were lower than that of Ce:H-BYB (∼400 photons/neutron).

Crystal growth and scintillation properties of (Na xCa 1−2xLu x−yNd y)F 2 single crystals

Na x Ca 1−2 x Lu x − y Nd y F 2 single crystals were grown from the melt using the precise atmosphere control type Micro-Pulling-Down (μ-PD) method to investigate their potential as a vacuum-ultraviolet (VUV) scintillators. The grown crystals were single-phase materials with fluorite-type structure (Fm-3m, Z = 4) as confirmed by XRD. The crystals demonstrated 80–90% transmittance above 200 nm wavelength and Nd 3+ 5d–4f luminescence (when exited by X-ray) observed around 185 nm. The radioluminescence measurements under 5.5 MeV α-ray excitation ( 241Am) demonstrated the light yield of 48 [Ph/5.5 MeV-α] and the decay time of 6.4–7.7 ns.

Evaluation of characterization of rare-earth doped sesquioxide ceramic scintillators

We investigated basic optical and scintillation properties of pure Y 2O 3, Tm 3+-doped Y 2O 3, pure Lu 2O 3 and Nd 3+-doped Lu 2O 3 transparent ceramics made by a sintering method. All ceramic samples showed 60–80% transparency, and some absorption bands due to Nd 3+ 4f–4f transition were observed in Nd 3+:Lu 2O 3 ceramic. Both Tm 3+:Y 2O 3 and Nd 3+:Lu 2O 3 ceramics showed sharp luminescence lines corresponding to the 4f–4f transition under 285 nm (Tm 3+:Y 2O 3) and 340 nm (Nd 3+:Lu 2O 3) excitation. The photoluminescence decay times were calculated to be about 24 μs for Tm 3+:Y 2O 3 and 1 μs for Nd 3+:Lu 2O 3, respectively. In radioluminescence measurements, Tm 3+ and Nd 3+ 4f–4f luminescence were observed for Tm 3+-doped Y 2O 3 and Nd 3+-doped Lu 2O 3 ceramics under 241Am 5.5 MeV α-ray excitation. Finally scintillation light yield was investigated with pulse height analysis.

Crystal growth and thermal neutron scintillation response of Ce doped K 6LiYF 5

K 6Li(Y 1− x Ce x )F 5 ( x = 0.003, 0.02) single crystals were grown from the melt using the precise atmosphere control type Micro-Pulling-Down (μ-PD) method to examine their potential as a new thermal neutron scintillators. The grown crystals were single-phase materials as confirmed by XRD. The crystals demonstrated 40–60% transmittance above 320 nm and Ce 3+ 5d–4f luminescence observed around 340 nm when exited by α-ray. The radio luminescence measurements under thermal neutron excitation ( 252Cf) demonstrated the light yield of 890 (Ph/neutron) and the decay time excited by α-ray exhibited 20 and 259 ns.

Compositional trends in low-temperature photoluminescence of heavily Er-doped GeS 2–Ga 2S 3 glasses

The influence of temperature and glass composition on the photoluminescence (PL) efficiency of Er 3+ ions embedded in (GeS 2) 100−x(Ga 2S 3) x (x = 20, 25 and 33 mol%) glasses has been studied. The typical 4f–4f emission bands of Er 3+ ions at around 830, 1000 and 1550 nm have been observed in the whole investigated temperature range from 300 K down to 10 K for all the compositions. New 4f–4f luminescence bands, in excess of the three basic ones, have been observed at 670, 870, 1120, 1260 and 1350 nm for (GeS 2) 75(Ga 2S 3) 25 glass composition, and are tentatively assigned to 2H 9/2 → 4I 11/2, 4G 11/2 → 4F 9/2, 2H 11/2 → 4I 11/2, 4F 7/2 → 4I 9/2 and 4F 3/2 → 4I 9/2 transitions, respectively. Thus a considerable influence of GeGaS host composition on the efficiency of 4f–4f transitions of embedded Er 3+ ions is documented with the outcome that (GeS 2) 75Ga 2S 3) 25 composition appears near optimal for the emission efficiency of Er 3+ ions. With decreasing temperature the PL efficiency is enhanced considerably with pronounced narrowing of all bands. In the case of the strongest PL band at ~ 1550 nm, corresponding to 4I 13/2 → 4I 15/2 transition, the narrowing at low temperature is further accompanied by the resolution of well pronounced fine structure due to “crystal field” splitting of corresponding electronic terms. The relationship between the photoluminescence and reflectance spectra as a function of Er content has been discussed.

Crystal growth, Nd distribution and luminescence properties of (Na0.425+xLu0.575−x−yNdy)F2.15−2x single crystals

(Na0.425+xLu0.575−x−yNdy)F2.15−2x (x=0, y=0, 0.001, 0.01, 0.05, 0.1, 0.2; x=±0.01, 0.02, 0.05, y=0.05) single crystals were grown from the melt using the precise atmosphere control type Micro-Pulling-Down (μ-PD) method to examine their potential as a new VUV scintillators. The grown crystals were single-phase materials with fluorite type structure (Fm−3m, Z=4) as confirmed by XRD and had good crystallinity. The distribution of the crystal constituents in axial and radial directions was evaluated, and only negligible non-uniformity along growth axis was detected. The crystals demonstrated 70–90% transmittance above 176–188nm wavelength and Nd3+ 5d–4f luminescence (when exited by X-ray) observed around 185nm. Both 5d–4f absorption and emission peaks shifted to longer wavelength region. The radioluminiscence measurements under 5.5MeV α-ray excitation (241Am) demonstrated the light yield of 35–90 [Ph/5.5MeV-α] and the decay time of 5.5–7.5ns.

Crystal structure and luminescence properties ofLiYP4O12:Ce3 + phosphor

LiYP4O12 polyphosphatedoped with Ce3 + ions was prepared by the melt solution technique. The crystal structure,interatomic distances, and atom coordination numbers were determined usingx-ray powder diffraction. A study of the spectral–kinetic luminescent propertieswas performed employing excitation with pulsed radiation from a synchrotron(UV–VUV range) and a laboratory x-ray source. The characteristics ofCe3 + luminescence, namely the emission doublet maxima at 3.97 and 3.72 eVand the 4f–5d excitation maxima at 4.20, 5.11, 5.40, 5.65 and 6.55 eV, arediscussed in terms of crystal field splitting in a low-symmetry site of theLiYP4O12 host lattice. Thelocation of the Ce3 + energy levels with respect to the valence and conduction bands of theLiYP4O12 host is estimated from the temperature dependence of the decay time measured forCe3 + 5d–4f luminescence.

Nd concentration dependence on the optical and scintillation properties of Nd doped BaF 2

Nd concentration dependence on the scintillation properties of Nd x Ba 1− x F 2+ x ( x = 0.001–0.5) crystals were investigated. From X-ray induced emission spectra, the intensity from an intrinsic luminescence of BaF 2 including core-valence luminescence and self-trapped-exciton (STE) emission were decreased with an increase of Nd concentration. Decay times under 241Am α-ray excitation were evaluated by the Photomultiplier Tube (PMT) Hamamatsu R8778 that was sensitive across the vacuum ultra-violet (VUV) and visible wavelength range. The average decay times indicated that Nd doped BaF 2 with lower Nd concentration has obviously slower decay times than that of samples with higher Nd concentration because the decay time of STE emission was slower than that of the core–valence luminescence in BaF 2 and the emission of 5d–4f transition on Nd 3+. The light yield of fast Nd 3+ 5d–4f luminescence was quite lower than STE emission of BaF 2.

Synthesis and luminescence properties of Ce 3+ doped nanoporous 12CaO·7Al 2O 3 powders and ceramics

Ce 3+ doped nanoporous 12CaO·7Al 2O 3 (C12A7) was synthesized using the self-propagating combustion method and solid state reaction. Ceramics of high density were produced using the melt-solidification process in a carbon crucible. The obtained samples were characterized using XRD and SEM methods and studied by means of low temperature time resolved luminescence under laser and synchrotron radiation excitation. It was shown that the Ce 3+ ion in C12A7 emits broad-band 5d–4f luminescence peaked at ∼3.0 eV. The decay curves of Ce 3+ emission in the studied samples have complicated nature depending on the excitation energy with the main decay component of 20–30 ns life time, typical for parity and spin allowed transitions of Ce 3+. The emission of Ce 3+ ions is efficiently excited through the intra-centre as well as in the intrinsic absorption region of C12A7.

Upconverted 5d–4f luminescence from Er3+ and Nd3+ ions doped into fluoride hosts excited by ArF and KrF excimer lasers

Abstract We report on observation of upconverted VUV luminescence due to 5 d –4 f radiative transitions in Er 3+ and Nd 3+ ions doped into some fluoride crystals, under excitation by ArF and KrF excimer lasers, respectively. Only spin-forbidden 5 d –4 f luminescence of Er 3+ (at 165 nm) was detected from the LiYF 4 :Er 3+ crystal whereas both spin-forbidden (at 169 nm) and spin-allowed (at 160.5 nm) components are observed from the BaY 2 F 8 :Er 3+ crystal, the latter being much weaker than in the case of one-photon excitation. Nd 3+ 5 d –4 f luminescence at 180 and 173 nm has been detected from the LiYF 4 :Nd 3+ and LaF 3 :Nd 3+ crystals, respectively. The shift of short-wavelength edge of 5 d –4 f emission spectra towards longer wavelengths is observed under temperature increase from 15 to 293 K. The observed effects in the spectra of Er 3+ and Nd 3+ doped crystals were interpreted as a result of reabsorption of 5 d –4 f luminescence escaping from the bulk of the crystals.

Temperature dependence of the Pr 3+ luminescence in LSO and YSO hosts

The temperature dependences of photoluminescence spectra of Pr 3+ in Lu 2SiO 5 (LSO) and Y 2SiO 5 (YSO) hosts under excitation into the 5d 1 excited state are reported within 4–450 K together with measured decay times of the fast and slow delayed recombination decay processes. Ionization processes occurring from the 5d 1 relaxed state are evaluated using the mentioned decay measurements. The simple kinetic model is created to provide quantitative parameters of energy barriers and frequency factors, which govern the ionization process in the 5d 1 Pr 3+ excited state in both hosts. The ionization barriers are interpreted as the separation between the conduction band and the 5d 1 excited state. The temperature dependences of the Pr 3+ 5d 1–4f and 4f–4f luminescence intensities point to the thermally stimulated transition from 5d 1 state towards the 3P 2 and other lower lying 4f levels.

Pr3+-doped complex oxide single crystal scintillators

We investigate and compare optical absorption, luminescence and scintillation properties of Pr-doped Y3Al5O12, Lu3Al5O12, Y2SiO5 and Lu2SiO5 single crystals. The processes determining the kinetics of the fast Pr3+ 5d–4f radiative transition are described. Among the studied host materials, only Lu3Al5O12 presents neither any 5d1–4f luminescence state nonradiative quenching nor Pr3+ ionization at room temperature. We evaluate the figure of merit of all materials for application as scintillators. The most promising system appears to be Lu3Al5O12 : Pr, since it combines an elevated density of 6.67 g cm−3, a fast scintillation response dominated by a 21 ns decay time and a spectrally corrected light yield about 160% with respect to that of Bi4Ge3O12 (BGO).

Growth and optical properties of Lu 3(Ga,Al) 5O 12 single crystals for scintillator application

Effect of Ga substitution in a (Ce,Lu) 3Al 5O 12 scintillator was examined at the crystals grown by the micro-pulling down(μ-PD) method. Strong suppression of unwanted host luminescence due to an exciton localized around Lu–Al antisite defect was observed even at the Ga concentration of 10 mol%. Less-intense slower components in scintillation decay were obtained upon increasing the amount of Ga. While the radioluminescence intensities of the 5d–4f luminescence of Ce 3+ were not strongly changed, light yield was increased by Ga substitution. The 20% Ga-substituted sample showed even higher light yield than typical Czochralski-grown Ga-free LuAG:Ce.

Heterometallic CoIII–LnIII (Ln = Gd, Tb, Dy) Complexes on a p‐Sulfonatothiacalix[4]arene Platform Exhibiting Redox‐Switchable Metal‐to‐Metal Energy Transfer

AbstractNuclear magnetic relaxation along with pH metric data have been used to reveal pH‐dependent heterometallic CoIII–LnIII (Ln = Gd, Tb, and Dy) complex formation on a p‐sulfonatothiacalix[4]arene (TCAS) platform in aqueous solution. The previously obtained 1D and 2D 1H NMR spectroscopic and X‐ray data prove the outer sphere binding of the CoIII block with the upper rim of TCAS, whereas the LnIII ion is coordinated with the phenolate groups of the lower rim of TCAS. The inclusive outer‐sphere binding of CoIII tris(dipyridyl) and tris(ethylendiaminate) complexes with the upper rim of TCAS favors binding of the inner‐sphere lanthanide ions through the lower rim of TCAS, whereas noninclusive binding of CoIII bis(histidinate) provides no effect on the binding of lanthanide ions. The emission properties of [Co(dipy)3]3+–LnIII (Ln = Gd, Tb, Dy) complexes indicate the quenching of 4f luminescence by the 3d block. This quenching can be switched off by electrochemical CoIII/CoII reduction with further switching on by reoxidation. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2008)

Interplay of spin-allowed and spin-forbidden 5d–4f luminescence from rare earth ions

The conditions for co-existence of emissions from spin-allowed and spin-forbidden 5d–4f transitions in rare earth ions and for thermal quenching of these emissions have been analyzed by taking Tm 3+ 5d–4f luminescence in LiYF 4:Tm 3+ and Lu 3+ 5d–4f luminescence in LuF 3 as examples. It is shown that temperature behavior of 5d–4f luminescence agrees with the common trends in decreasing energy splitting between the lowest high-spin and low-spin 5d levels as well as decreasing energy gap between the lowest 5d level and the bottom of the conduction band of the host crystal towards heavier rare earth ions (from Er 3+ to Lu 3+).

Scintillating properties of Pr-doped YAlO3 single crystals grown by the micro-pulling-down method

Pr-doped YAlO3 (0.1, 0.5, 1, 2, 3, 4, 5, and 6 mol % Pr6O11) single crystals were grown by the micro-pulling-down method and their optical and luminescence properties were investigated in the range 80–300 K. Dominant 5d–4f double-peak emission at 254 and 282 nm was observed both in radio-and photoluminescence, and was accompanied by weak 4f–4f luminescence at 495 and 620 nm. The 5d–4f emission shows almost no temperature dependence below 300 K, and achieved radioluminescence intensity is more than 15 times higher than that of Bi4Ge3O12.

Growth and Luminescence Properties of Pr-doped Lu3(Ga,Al)5O12 Single Crystals

Single crystals with the nominal composition of (Pr0.01,Lu0.99)3(Gax,Al1-x)5O12 (Pr:LuGAG) were grown by the micro-pulling-down (µ-PD) method with RF heating and their luminescence properties were characterized. Transparent and crack free crystals that were slightly yellowish green were obtained. Lattice constants and densities systematically increased with increasing of Ga concentration. The luminescence properties of Pr:LuGAG were characterized by photoluminescence spectra and decays, radioluminescence spectra and light yield measurements. 5d–4f luminescence was observed for the x≤0.6 samples. It was found that the 5d–4f emission of Pr3+ is quenched only slightly up to x≤0.4 whereas density systematically increased in the range of 0≤x≤1.0.

Luminescence determination of praseodymium in solutions of its β-diketonates

With the aim of a search for new analytical forms for the determination of praseodymium(III), its 4f luminescence was studied in solutions of mixed-ligand complexes with fluorinated β-diketones and donoractive ligands (1,10-phenanthroline, neocuproine, diantipyrylmethane, diantipyrylpropylmethane, and trioctylphosphine oxide). It was found that the luminescence intensity of praseodymium(III) depends on both the character of the fluoroalkyl substituent in the β-diketone molecule and the nature of the second ligand. The complex of praseodymium(III) with thenoyltrifluoroacetone and diantipyrylpropylmethane was used for the determination of praseodymium in some optical materials. The lower determination limit of praseodymium was 0.01 μg/mL.

Optical and gain properties of series of crystals LiF–YF 3–LuF 3 doped with Ce 3+ and Yb 3+ ions

Here, we present first results of systematic studies of host cation variation impact on spectral-kinetic, photochemical and gain properties of Ce 3+-doped LiYF 4 (YLF), LiLuF 4 (LLF) and LiY 1− x Lu x F 4 family crystals. 5d–4f luminescence decay of Ce 3+ ions studies, together with pump–probe experiments, indicate that previously reported twice higher luminescence quantum yield in LLF compared with that of YLF crystals is provided by more efficient upper lasing level feeding due to recombination and higher color center destruction rate in LLF against YLF crystals. Namely, it is responsible for higher energetic characteristics of laser based on Ce 3+:LLF crystals. Strong and wide pump-induced absorption band centered at 310 nm is observed in Ce 3+:YLF. This band is shifted to blue and its intensity goes down with Lu content. We have evaluated free charges recombination rate, excited state absorption cross-section for Ce 3+ ions and some other photodynamic processes related microparameters. Fitting results indicate that pump-induced color centers lifetime decreases with Lu-content in LiYF 4–LiLuF 4 mixture and it can be associated with more efficient color center bleaching by Ce 3+ ions 5d–4f fluorescence.