EXAFS investigation and luminescent properties of nanosized Tb: Lu2O3 phosphors

Nanosized terbium doped Lu2O3 phosphors were synthesized via a modified co-precipitation processing.The as-prepared Tb:Lu2O3 phosphors was consisted of well crystallized nanosized sphere particles with a diameter of about 30 nnx Local structure of Tb ions in Lu2O3 lattice was investigated by an analytical approach based on Fourier transformation of the extended X-ray absorption fine structure(EXAFS) data.X-ray near edge structure (XANES) spectra suggested that all Tb ions doped were tervalonce.EXAFS results indicated that Tb ions have entered the Lu2O3 cubic lattice by means of solid solution.The coordination number and first shell Tb-O distance dropped with the increasing of Tb concentration.Emission spectra of the phosphors was shown to be typical for Tb3+ with main components at 542,550 and 490 nm,derived from irradiative relaxation of 5D4 level.The emission intensity decreased severely with the increasing of Tb concentration from 1 mol.% to 15 tool.%,suggesting a significant concentration quenching above 1 mol.% Tb.The reduction of emission intensity was interpreted by higher distortion derived relaxation among the surface state resident Tb3+ ions.     

Thermoluminescence Characteristics of SrB6O10 ： Tb

SrB6010：Tb phosphor was synthesized by high-temperature solid state reaction. The influences of Ce or Li as a co-dopant, Tb concentration and irradiation dose exposure on TL of SrB6010 ： Tb were investigated. Results show that Ce or Li as a co-dopant can not improve the sensitivity of SrB6010：Tb phosphor. TL response depends on Tb concentration and 0.02 is the optimum in the concentration range from 0.01 to 0.10. Using the optimum Tb concentration, we calculated the kinetic parameters of SrB6010：Tb employing the peak shape method, and suggested the phosphor obeying the second order kinetics. TL emission intensity is linearly dependent on the irradiation dose within the dose range of 50 - 200 Gy. The characteristic Tb^3＋ ion emission was observed in TL emission spectrum.     

Glass forming regions and concentration-dependent luminescence properties of Tb~(3+)-activated tellurium-lutetium-tungsten glasses

The glass-forming regions of tellurium-gadolinium-tungsten ternary system prepared at 1000℃for 60 min were firstly determined.To improve density,the full replacement of lutetium for gadolinium to form Tb³⁺-activated tellurium-lutetium-tungsten glasses with the composition of 64 TeO₂-20 WO₃-(16-y)Lu₂O₃-yTb₂O₃were designed for scintillation application.The concentration-dependent optical properties of Tb³⁺-activated tellurium-lutetium-tungsten glasses were fully investigated by transmittance,excitation and emission spectra,together with the luminescence decay curves.The energy transfer mechanism was discussed according to Huang’s rule.The optimized 4 mol%Tb₂O₃activated tellurium-lutetium-tungsten glasses with the density of 6.49 g/cm³and the lifetime of 0.551 ms are developing to be suitable for the potential detection of slow events in the future work.     

First-principles study of electronic structure and optical properties of Er:Lu2O3

In the present computational study,we found that Er:Lu₂O₃materials have promise for application in laser applications.The crystal structure and the electronic and optical properties of Er:Lu₂O₃materials were studied using first-principle calculations under the framework of density functional theory.Based on the experimental and calculated results,the structure of Lu₂O₃was established.The calculated results show that doping by Er³⁺can effectively improve its absorption coefficient in the ultraviolet region and improve the static dielectric constant of Lu₂O₃.As the doping concentration of Er³⁺increases,the energy of the valence band electrons excited to the conduction band decreases,and the transition is more likely to occur.The absorption coefficient,reflectance,and electron energy loss spectroscopy are bathochromic shifted.The Lu_2-xEr_xO₃(02O₃.     

Energy transfer and luminescent properties of Tb3+ and Tb3+, Yb3+ doped CNGG phosphors

In this work,calcium niobium gallium garnet(Ca₃ Nb_1.6875Ga_3.1875O₁₂-CNGG) ceramic samples singledoped with Tb³⁺ and co-doped with Tb³⁺ and Yb³⁺ ions were sintered by the solid-state reaction method.The structural characterization of the samples was carried out by X-ray diffraction measurements.The optimal concentration of Tb³⁺ ions corresponding to the maximum luminescence in the green spectral range in CNGG:...     

Luminescent properties of β-Lu2Si2O7:RE(RE=Ce, Tb) nanoparticles by sol-gel method

Nanoscale RE³⁺ (RE=Ce, Tb) doped and codoped lutetium pyrosilicate Lu₂Si₂O₇ (LPS) phosphors were prepared by using the sol-gel method. Heat treatment was performed in the temperature range from 900 to 1100 °C. The crystal structure was analyzed by X-ray diffraction (XRD). The results showed that the β-type structure of LPS was obtained at 1100 °C. The excitation spectra in the UV and VUV ranges and the emission spectra of the samples were measured at room temperature, and their luminescent properties were studied. The energy transfer from Ce³⁺ to Tb³⁺ in the codoped samples were observed and discussed.     

Thermally stable photoluminescence and long persistent luminescence of Ca3Ga4O9:Tb3+/Zn2+

A green long persistent luminescence (LPL) phosphor Ca₃Ga₄O₉:Tb³⁺/Zn²⁺ was prepared. Ca₃Ga₄O₉ matrix exhibits blue self-activated LPL due to the creation of intrinsic traps. When Tb³⁺ is doped, the photoluminescence (PL) and LPL colors change from blue to green with their intensities significantly enhanced. The doping of Zn²⁺ evidently improves the PL and LPL performances of the Ca₃Ga₄O₉ matrix and Ca₃Ga₄O₉:Tb³⁺. The thermoluminescence (TL) spectra show that a successive trap distribution is formed by multiple intrinsic traps with different depths in the Ca₃Ga₄O₉ matrix, and the incorporation of Tb³⁺ and Zn²⁺ effectively increases the densities of these intrinsic traps. The existence of a successive trap distribution makes the Ca₃Ga₄O₉:Tb³⁺/Zn²⁺ phosphor exhibit thermally stable PL and LPL. It is indicated that this phosphor shows great promise for the application such as high-temperature LPL phosphor.     

Influence of dysprosium concentration on sensitivity of luminescent thermometers of phosphors Ca_9Tb(PO_4)_5(SiO_4)F_2

Tb~(3+),Dy~(3+)-co-doped Ca_9 Tb_xDy_(1-x)(PO_4)_5(SiO_4)F_2 phosphors were prepared via high-temperature solidphase reaction method and the potential application in optical temperature measurements due to their color-tunable property was investigated in detail.The photoluminescence emission(PL) and photoluminescence excitation(PLE) spectra results show that the as-prepared phosphors exhibit both Tb~(3+) and Dy~(3+) emissions at 546 nm(~5 D_4-~7 F_5 transition of Tb~(3+)) and 587 nm(~4 F_(9/2)-~6 H_(13/2) transition of Dy~(3+)) upon376 nm excitation,respectively.In addition,the fluorescence decay analysis shows that the lifetime of the Tb3+emission rapidly decreases,which confirms the energy transfer existence between Dy~(3+) and Tb~(3+).Under 376 nm excitation,the temperature dependence of the fluorescence intensity ratios for the dualmission bands peaked at 546 and 587 nm was studied in the temperature range from 303 to 573 K.The results show that with the increase of Dy~(3+) concentration,the relative sensitivity first increases and then decreases,what's more,the maximum relative sensitivity is 3.142×10~(-3)%/K for Ca_9 Tb_xDy_(1-x)(PO_4)_5(SiO_4)-F_2(x=0.4).As a consequence,this preliminary study provides a novel method for exploring the novel thermo meters.     

Luminescence properties of BaAl12O19:Tb,Ce and energy transfer between Ce3+, Tb3+

BaAl₁₂O₁₉:Tb,Ce phosphors were prepared by sol-gel technique, the crystalline structures of samples characterized by XRD, and the luminescence properties and energy transfer between Ce³⁺ and Tb³⁺ were investigated. The results indicated that the emission intensity and the excitation wavelength range of Tb³⁺ increased when Ce³⁺ was doped. It demonstrated that the Ce³⁺ added in the BaAl₁₂O₁₉:Tb could deliver energy to Tb³⁺, and Ce³⁺ was not luminous by itself. The relative emission intensity of Tb³⁺ at wavelength of 548 nm was the strongest by Tb³⁺/Ce³⁺ ratio of 2:1, when excited at 310 nm, which was the characteristic adsorption wavelength of Ce³⁺.     

Blue-emitting Sr_(1-x)Ca_xLu_2O_4:Ce~(3+) phosphors for high CRI white LEDs

A broadband blue-emitting Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+)(x=0-0.2) phospho rs were synthesized,which can be used for near-UV pumped white light-emitting diodes(w-LEDs).The crystal structures,photoluminescence pro perties,external quantum efficiency,the rmal stability and application perfo rmance of Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+),by partially substituting Sr~(2+) with Ca~(2+)(x=0-0.2),were studied by various analytical techniques.When the Ca/Sr ratio of Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+) gradually increases,the emission peak of Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+) red-shiftes from 459 to 465 nm,corrected external quantum efficiency increases from 31.8% to 42.9%,and the thermal stability is also improved.The mechanism of the changes of the photoluminescence emission and excitation spectra,external quantum efficiency and thermal stability properties was also investigated in detail.In addition,a w-LED was fabricated by using SrLu_2 O_4:Ce~(3+)(blue),β-sialon:Eu~(2+)(green) and(Sr,Ca)AlSiN_3:Eu~(2+)(red) phosphors combined with a 405 nm near-UV LED chip,and its color rendering index(CRI) reaches 96.0.When Sr_(0.8)Ca_(0.2)Lu_2 O_4:Ce~(3+)is applied as blue phosphor to substitute SrLu_2 O_4:Ce~(3+),the obtained w-LED devices have high luminous efficiency,and CRI greater than 95.0.These re sults show that the Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+) can be potential blue phosphors for n-UV pumped high CRI w-LEDs application.     

Synthesis, crystal structures and characterization of a pair of TbIII-based enantiomers

A pair of novel Tb^III-based enantiomers, [Tb(dbm)₃·L_SS] (1) and [Tb(dbm)₃·L_RR] (2) (where L_SS=(+)-4,5-pinene bipyridine, L_RR= (-)-4,5-pinene bipyridine, dbm=dibenzoylmethanate), were synthesized and characterized based on single crystal X-ray diffraction, elemental analysis, FT-IR, TG and CD spectra. X-ray diffraction analysis showed that both the complexes crystallized in monoclinic crystal system with P2₁ chiral space group. The Tb^III ion was eight-coordinated by six O atoms of three dbm ligands and two N atoms from one chiral ligand L_SS or L_RR. The CD spectra revealed that complexes 1 and 2 were enantiomers. Thermogravimetric analysis results indicated that 1 and 2 were thermally stable up to 246 °C.     

Synthesis,photoluminescence properties and thermal investigation by TG-MS of RE(DAS)_3·xH_2O(RE=Eu~(3+),Tb~(3+))

Rare earth(Ⅲ) diphenyl-4-amine sulfonates(RE(DAS)_3·xH_2O,RE=Eu~(3+),Tb~(3+))phosphors were synthesized by precursor method from barium diphenyl-4-amine sulfonate and rare earth sulfates.FTIR,TG/DSC coupled to mass spectrometry(TG/DSC/MS),X-ray powder diffraction(XPD),scanning electron microscopy(SEM) and photo luminesce nce(PL) spectroscopy were utilized to structurally and morphologically characterize the samples.Thermal decomposition of Eu(DAS)_3·7H_2O and Tb(DAS)_3·2H_2O at 973 K under dynamic air atmosphere results in crystalline Eu_2O_2SO_4 and Tb_2O_2SO_4 materials,respectively.Accordingly,MS spectra reveal the liberation of thermal decomposition products of precursors,largely as CO_2,NO_2 and SO_2 gases.The diphenyl-4-amine sulfonate(DAS) ligand demonstrats a good stabilizing property for Eu~(3+) and Tb~(3+) ions.The Eu(DAS)_3·7H_2O and Tb(DAS)_3·2H_2O compounds display efficient red and green emissions,under UV excitation,arising from the ~5D_0→~7F_J(J=0-4) and ~5D_4→~7F_J(J=0-6) transitions of the Eu~(3+) and Tb~(3+) ions,respectively.     

VUV spectroscopic properties of rare-earth（RE=Eu,Tb and Dy）-doped A2Zr（PO4）2（A=Li,Na and K） phosphates

This study fully investigated the vacuum ultraviolet excitation spectra of pure and rare-earth（RE=Eu, Tb and Dy）-doped A2Zr（PO4）2（A=Li, Na and K） phosphors. The synthesized Na and Li compounds were characterized by XRD showing two new types of phases after indexation. Although these three pure compounds had different crystal structures, they exhibited similar luminescence properties. For Eu3＋-activated samples, the broad excitation band centered at 217 nm could be attributed to the CT transition between O2–（2p6） and Eu3＋ ions. For Tb3＋-doped samples, two groups of f-d transitions were observed, where a strong broad band at 221 nm was due to the spin-allowed f-d transition. Energy transfer from O2– to Dy3＋was not observed in Dy3＋-doped phosphors, probably because it overlapped considerably with the CT transition from O2– to Zr4＋ at 187 nm.     

Synthesis, crystal structure and characterization of one-dimension complex constructed by terbium（III） and 2-iodobenzoate

The complex of [Tb(2-IBA)₃(H₂O)₂]_n (2-IBA=2-iodobenzoate)was prepared by solvent method from TbCl₃·6H₂O and 2-iodobenzoic acid. The crystal structure was determined with X-ray single-crystal diffraction. The X-ray diffraction analysis indicated that the title complex crystallized in triclinic crystal system and Pī space group. The Tb³⁺ ion was coordinated by six oxygen atoms from five 2-IBA ligands and two oxygen atoms from two water molecules, giving a distorted square-antiprism polyhedral geometry. The carboxyl groups were bonded to the Tb³⁺ ions with bidentate-bridging and bidentate-chelating coordination modes. The adjacent Tb³⁺ ions were linked by two bidentate-bridging 2-IBA ligands, forming 1-D chain structure. The fluorescence spectrum of the complex showed four main peaks at 489, 543, 587, and 618 nm, corresponding to ⁵D₄→⁷F_J (J=6?3) transition emissions of the Tb³⁺ ion, respectively.     

Structure regulation for ultra-high luminescence quantum yield lanthanide complex and simultaneous detection of cancer marker and ferrous ion

The exploitation of a highly selective and sensitive probe to detect both cancer marker and metal ion is of great importance.In this work,the "one stone two bird" agent of 1,10-phenanthroline(phen) is designed to disrupt the polymeric lanthanide MOFs(LnMOFs,[Ln(CHO_2)_3]n,Ln=Tb,la;Eu,1 b,CHO2=formic acid) {[Ln(CHO_2)_4·(C_2 H_8 N)]_n,Ln=Y,2 a;Gd,2 b;Dy,2 c,C_2 H_8 N=dimethylamine}) into a soluble mononuclear species [Ln(phen)2(NO_3)_3,Ln=Tb,3 a;Eu,3 b] as well as to provide an antenna for efficient photons absorption,resulting in an ultra-high luminescence quantum yield(QY,90%) europium complex.The luminescence QY is among the highest record of monomeric(zero-dimensional) lanthanide complexes.Furthermore,mononuclear Tb3+complex(3 a) functions as a multiplex sensor towards both Fe2+and cancer marker of 5-hydroxyindole-3-acetic acid(5-HIAA).Importantly,the limit of detection(LOD)for sensing 5-HIAA is an ultra-sensitive value of 1 × 10 s mol/L,which is even lower than that necessary for the early diagnosis of carcinoid tumors.More interestingly,sensing results in simulated urine reveals that 3 a has potential application for early diagnosis in the clinic.     

Dislocation structure,phase stability,and yield stress behavior of L1<Subscript>2</Subscript> intermetallics: Ir<Subscript>3</Subscript>X (X = Ti,Zr, Hf,V, Nb,Ta)

The structure and mobility of superdislocations in Ir₃X (X = Ti, Zr, Hf, V, Nb, Ta) with L1₂ structure were investigated in the framework of the modified Peierls-Nabarro (PN) model with first-principles generalized stacking fault energetics calculated using the all-electron full-potential linearized augmented plane wave method (FLAPW). Superlattice intrinsic stacking fault (SISF)-bound superdislocations (Kear splitting scheme) are strongly preferred energetically in Ir₃V, Ir₃Nb, and Ir₃Ta, whereas antiphase boundary (APB)-bound superdislocations (Shockley splitting scheme) are predicted in Ir₃Ti, Ir₃Zr, and Ir₃Hf. Because APB-bound superdislocations are considered responsible for the yield stress anomaly, our results predict that positive yield stress temperature dependence could only be expected in Ir₃Ti, Ir₃Zr, and Ir₃Hf, and a negative one in Ir₃V, Ir₃Nb, and Ir₃Ta. The connection of the mechanical behavior of the Ir₃X alloys with the L1₂ → D0₁₉ structural instability is established and the electronic origins of this instability are analyzed. This article is based on a presentation made in the symposium entitled “Beyond Nickel-Base Superalloys,” which took place March 14–18, 2004, at the TMS Spring meeting in Charlotte, NC, under the auspices of the SMD-Corrosion and Environmental Effects Committee, the SMD-High Temperature Alloys Committee, the SMD-Mechanical Behavior of Materials Committee, and the SMD-Refractory Metals Committee.     

A comparison research on replacements of Ba2+ by Lu3+ and Ba2+-Si4+ by Lu3+-Al3+ in BaSi2O2N2:Eu phosphors

As a cyan-emitting oxonitridosilicate phosphor,BaSi₂O₂N₂:Eu²⁺can be used as a competent cyan compensator to improve the color rendering index of white light-emitting diodes(WLEDs).However,low luminescence efficiency and poor thermal stability of this type of phosphor seriously suppress its actual application in full-spectrum lighting.The replacements of Ba²⁺by Lu³⁺and Ba²⁺-Si⁴⁺by Lu³⁺-Al³⁺can greatly increase the luminescence intensity and improve the thermal stability at the same time.With Lu³⁺doping,the internal quantum efficiencyηIQE Ba_0.925Si₂O₂N₂:0.03 Eu²⁺,0.045 Lu³⁺is 24.08%higher than that of Ba_0.97Si₂O₂N₂:0.03 Eu²⁺.After Al³⁺co-doping,theηIQE is further increased by 10.31%compared to Ba_0.925Si₂O₂N₂:0.03 Eu²⁺,0.045 Lu³⁺.When the temperature rises to 473 K,the luminescence intensity of Ba_0.925Si₂O₂N₂:0.03 Eu²⁺,0.045 Lu³⁺maintains 62.32%of that at room temperature,which increases by 17.35%in relative to the Ba_0.97Si₂O₂N₂:0.03 Eu²⁺,while the luminescence intensity of Ba_0.925Si_1.97O₂N₂:0.03 Eu²⁺,0.045 Lu³⁺,0.03 Al³⁺keeps 73.87%of the initial value,which increases by18.52%compared to Ba_0.925Si₂O₂N₂:0.03 Eu²⁺,0.045 Lu³⁺.The mechanisms for luminescence and thermal stability improvement are proposed.The Ba_0.925Si_1.97O₂N₂:0.03 Eu²⁺,0.045 Lu³⁺,0.03 Al³⁺cyan phosphor,Y3 Al5 O12:Ce3+yellow phosphor and CaAlSiN3:Eu²⁺red phosphor are mixed thoroughly and coated on a blue LED(450 nm)to assemble a WLED.The WLED demonstrates a color rendering index(Ra)of 97.1 at150 mA,and the R1-R15 values are all above 90.The results indicate that as an effective cyan compensator in WLED,the BaSi₂O₂N₂:Eu²⁺,Lu³⁺,Al³⁺phosphor has great application prospect in the field of full-spectrum lighting.     

An investigation of high temperature thermodynamic properties in the Pt-Zr and Pt-Hf systems

High-temperature thermodynamic properties of Pt−Zr alloys containing 2 to 25 at. pct Zr and Pt−Hf alloys containing 20 to 25 at. pct Hf have been measured over the temperature range 1100 to 1400 K by a galvanic cell technique using a thoria-based electrolyte. Activities of Zr and Hf show large negative deviations from Raoult's Law; at 1300 K and 23 at. pct Zr of Hf, for instance,a _Zr=6.5×10⁻¹⁶ anda _Hf=7.9×10⁻¹⁷. Correlation of emf results with X-ray phase data enables calculation of standard free energies of formation of the intermetallic compounds ZrPt₅, ZrPt₃, and HfPt₃. At 1300 K ΔG _f ⁰ (ZrPt₅) =−92,680 cal/mole; ΔG _f ⁰ (ZrPt₃)=−91,740 cal/mole; and ΔG _f ⁰ (HfPt₃)=−97,350 cal/mole. The high stabilities of phases in the Pt−Ti, Pt−Zr, and Pt−Hf systems verify the predictions of the Engel-Brewer correlation. The large negative entropies of formation of TiPt₃, ZrPt₃ are discussed. Applications including side reactions in fuel cells and thermocouple systems are mentioned. P. J. MESCHTER, formerly a Graduate Student at the University of Pennsylvania This paper is based upon a dissertation submitted by P. J. Meschter in partial fulfillment of the requirements of the degree of Doctor of Philosophy at the University of Pennsylvania.     

Interaction of TbCl3 and lanthanide complexes with poly（N-vinylpyrrolidone）

The interaction of TbCl3 and lanthanide(III) β-diketonate complexes with poly(N-vinylpyrrolidone)(PVP) polymer was studied using fluorescence spectroscopy. In the presence of PVP the emission of Tb3+ in ethanolic solution of TbCl3 significantly increased owing to the excitation energy transfer from PVP to Tb3+ ions, which was more efficient as compared to a direct excitation of the Tb3+ 4f75d1 levels. In contrast, emission of NEt4Tb(hfa)4 and NEt4Eu(hfa)4 complexes was almost completely quenched in solution containing PVP. The PVP bound both Ln3+ ions and hfa ligands which caused decomposition of Ln-hfa complexes and switched off the excitation energy transfer from the ligand to the emitting Ln3+ ion. The important role of hydrogen bonds in stabilization of interaction of hfa ligands with PVP was indicated.     

Hydrogen detrapping from grain boundaries and dislocations in high purity iron

Hydrogen detrapping in high purity iron was studied by measuring evolution rates of quenched-in hydrogen from 80 to 800 K using a quadrupole mass spectrometer in an ultra high vacuum system. The peak of the evolution rate was observed at 395 K in single crystal specimens and 415 K in polycrystalline specimens with a heating rate of 1 K min⁻¹. Effects of grain size and deformation on the evolution rate was also studied. It was shown that the results are consistent with the evolution rates calculated with the binding energy B = 0.51 ± 0.02 eV and the trap density term γC_{T = (4 ∼ 15) × 10⁻⁵} in polycrystalline iron, and B = 0.47 ± 0.02 eVand γC_T = (2 ∼ 13) × 10⁻⁵ in single crystal iron. The dominant traps are considered to be grain boundaries in polycrystalline specimens and dislocations in single crystal specimens.