Influence of the chromium and ytterbium co-doping on the photoluminescence of zinc selenide crystals

The luminescent properties of ZnSe, ZnSe：Cr（0.05 at.% Cr）, ZnSe：Yb（0.03 at.% Yb） and ZnSe：Cr：Yb（0.05 at.% Cr, 0.05 at.% Yb） crystals, doped during the growth process by the chemical vapor transport method, were studied within the temperature interval of 6–300 K. At the 6 K temperature in the visible spectral range 2 bands were observed： a band in the excitonic spectral region and a band of self-activated luminescence. It was shown that co-doping of zinc selenide crystals with the chromium and ytterbium led to the combination of the impurities influence on the photoluminescent properties. At the liquid helium temperature in the middle infrared range of the spectra of the ytterbium and chromium co-doped crystal a band with the maximum localized at 1.7μm was observed, which was overlapped with a complex band in the middle-IR spectral range, characteristic for the chromium doped ZnSe crystals. On the basis of obtained data an interaction mechanism of the chromium and ytterbium co-doping impurities was proposed. Guided by the existent model of the ytterbium ion incorporation in the selenide sublattice of the ZnSe crystals, an assumption about stabilization of single charged chromium ions in the zinc sublattice crystal nodes, by means of formation of the local charge compensating clusters, was made. It was assumed that the resonant energy transfer from one chromium ion to another,which led to the concentration quenching of the IR emission in the ZnSe：Cr PL spectra, would lead to the broadening of the IR emission in the spectra of ytterbium and chromium co-doped zinc selenide crystals.g     

Luminescence properties of nitride red phosphor for LED

Eu^2＋-doped ternary nitride phosphor, Sr2Si5N8：Eu^2＋, was synthesized using the high temperature solid-state method. The X-ray diffraction （XRD） pattern showed that Sr2Si5N8 single phase was obtained. The lattice parameters shrank because the radius of Eu^2＋ was smaller than that of Sr^2＋. The emission spectra showed a broad emission band. With an increase in Eu^2＋ concentration, the emission peak position was redshifted. The excitation spectra showed two excitation bands originating from the host and the 4f^7→4f^6 5d^1 transition of Eu^2＋ ions Compared with the luminescent characteristic of Sr2Si5N8：Eu^2＋ and CaS：Eu^2＋ phosphors, at different temperatures, it was noted that the intensity of the two phosphors reduced gradually with an increase in temperature. The intensity of Sr2Si5N8：Eu^2＋ phosphor was stronger than that of CaS：Eu^2＋, which indicated that the luminescent characteristic of the former was better than that of the latter.     

Optical properties of Eu2+-doped strontium borate glasses containing F- and Li+ ions

In this experiment, strontium borate glasses were prepared using the conventional quenching method in air atmosphere. Optical absorption, photoluminescence excitation and emission spectra, X-ray excited luminescence (XEL), and luminescence decay curve of the as-prepared glasses were investigated at room temperature. The as-prepared glasses had two kinds of Eu ions, i.e., Eu2 and Eu3 . Compared with the reported results of strontium borate glasses, Eu2 luminescence was enhanced in the studied strontium borate glasses coprepared with F- and Li ions. The coexisting of Li or F- in the borate glasses could create more negative defect VSr″ and stabilize Eu2 ions, which might act as donor of electrons;For the F- doping, the new center of B(O, F)4 (or BO3F) and BO2F2 units could be considered to be the distorted (BO4), which were needed as a rigid framework to stabilize the divalent rare earth ions.     

Preparation and luminescence properties of the red-emitting phosphor（Sr1-xCax）2Si5N8：Eu^2＋ with different Sr/Ca ratios

A series of Eu2+-doped ternary nitride phosphors, with a formula of (Sr1-xCax)2Si5N8: Eu2+, were synthesized by high-temperature solid-state method. The structure and luminescence properties were characterized, indicating the potential application as a red phosphor in the phosphor-converted white light-emitting diodes. The X-ray diffraction patterns showed that the Sr2Si5N8 and Ca2Si5N8 phases were generated at each end of (Sr1-xCax)2Si5N8: Eu2+ and coexisted in the range of 0.5≤x≤0.75. The emission spectra showed broad emission bands originating from the 4f65d1→4f7 transition of Eu2+ ions. The emission peak changed with the variations in Ca2+ concentration.     

Photo-Catalyzed Rare Earth Materials with Ability to Translate Free Radicals into Negative Ions

Negativeionsmeansinglegasmoleculeand lightiongroupwithnegativecharges.Thereare manykindsofnegativeionsincludingelectronsand othernegativeionsfromgasmoleculesreactionfor exampleas·O-2.Afteragooddealofobservation andclinicexperiment,amongnegativeions,hydra…     

Synthesis, structure and luminescence properties of KEu0.01Gd0.19Yb0.8（WO4）2 powder

The synthesis of co-doped KEu_0.01Gd_0.19Yb_0.8(WO₄)₂ was achieved by a modified Pechini method at 750 °C. The structure of obtained compound was confirmed using X-ray diffraction measurement and Raman spectroscopy. The Scherrer's formula was used to confirm the grain sizes visualized by TEM technique. The grain sizes of about 100 nm of monoclinic KGW were successfully obtained by this methodology. In order to study spectroscopic properties of the prepared system the emission spectra were measured. The effective down- and up-conversion processes in non-resonant system were investigated.     

Luminescence enhancement of rare earth ions by metal nanostructures

Well-ordered metal structures, i.e. arrays of nanosized tips on silver surface for studies of the luminescence enhancement of absorbed media with rare earth ions were used. These arrays were prepared by the metal evaporation on track membranes. Calculations of resonance frequencies of tips regarded as semispheroids were done taking into account the interaction between dipoles of tips. They were used to discuss experimental results for media with Eu(NO₃)₃·6H₂O salt basing on data for bulk silver dielectric function.     

Influence of non-covalent interactions on properties of lanthanide systems with aromatic ligands

Two series of lanthanide compounds, namely, chlorides containing different numbers of both 1,10-phenanthroline （Phen） molecules and chloride anions in the first coordination sphere, and Schiff Bases （SBs） derived from Pyridoxal （PL） and amino acids, were characterized by single crystal X-ray diffraction and luminescence techniques. The combined use of these techniques for the analysis of long-distance europium non-covalent interactions was performed for the first time. As a result, the correlation between supramolecular organization and the features of the Eum electronic transitions was found for the compounds of the first series. Strong non-covalent interactions between pyridoxal tings of SBs （the second series of compotmd） led to the formation of 1：2 species and four-dentate coordination function of these SBs in aqueous solution.     

Strong dependence of upconversion luminescence on doping concentration in holmium and ytterbium co-doped Y2O3 phosphor

Under the excitation of 980 nm diode laser, intense green emission (5F4+5S2-5I8) of Ho3+ was observed in Ho3+ and Yb3+ co-doped cubic Y2O3. The doping concentration and laser power dependence of the upconverted emission were studied. The decay curves of 5F4+5S2 emission of Ho3+ under the excitation of 355 nm pulse laser were measured to investigate the energy transfer process between Ho3+ and Yb3+. The results indicated that two-photon process was responsible for the upconversion (UC) emission. The Ho3+ con...     

Luminescent Properties of Bi-Rare Earth Complexes with m-methylbenzoic Acid and 1, 10-phenanthroline

Ｔｈｅｒｅｈａｓｂｅｅｎａｇｒｏｗｉｎｇｉｎｔｅｒｅｓｔｉｎｔｈｅｌｕｍｉｎｅｓｃｅｎｃｅｐｒｏｐｅｒｔｉｅｓｏｆｌａｎｔｈａｎｉｄｅｃｏｍｐｌｅｘ ｅｓｗｉｔｈｏｒｇａｎｉｃａｃｉｄｓ ,ｓｕｃｈａｓａｒｏｍａｔｉｃａｃｉｄｓｏｒｐｈｔｈａｌｉｃａｃｉｄｓｂｅｃａｕｓｅｏｆｔｈｅｉｒｐｏｔｅｎｔｉａｌｃｈｅｍｉｃａｌａｎｄｂｉｏｌｏｇｉｃａｌａｐｐｌｉｃａｔｉｏｎｆｏｒｐｒｏｂｅｓａｎｄｌａｂｅｌｓ .Ｅｕ3 + ａｎｄＴｂ3 + ｈａｖｅｍｏｒｅｅｘｃｅｌ ｌｅｎｔｌｕｍｉｎｅｓｃｅｎｃｅｐｒｏｐｅｒｔｉ…     

Up-conversion processes of rare earth ions in heavy metal glasses

Heavy metal lead germanate glasses doubly doped with Yb3+ and Ln3+ ions(Ln=Er,Tm) were investigated.Up-conversion spectra of Er3+ and Tm3+ were registered under diode-laser excitation of Yb3+.Up-conversion luminescence bands corresponded to 4S3/2→4I15/2(green) and 4F9/2→4I15/2(red) transitions of Er3+ as well as 1G4→3H6(blue) and 3H4→3H6(NIR) transitions of Tm3+,respectively.     

Relationship between Crystal Structure and Luminescence Properties of （Y0.96-x Lnx Ce0.04 ）3 Al5 O12 （LH=Gd,La, Lu） Phosphors

The doping effects of La^3＋, Gd^3＋ and Lu^3＋ on the crystal structure and luminescence properties of （Yo96-x LnxCe0.04）3Al5O12（Ln = Gd, La, Lu） phosphors were studied. The X-ray diffraction patterns presented that with the inerease of the doping concentrations of La^3＋ and Gd^3＋ ions, the d-value of （Y0.96-xLnxCe0.04）3Al5O12 （Ln = Gd, La） inereased and the larger the doping ion, the stronger the effect would be. The doping amount causing phase transition in （Y0.96-xLnxCe0.04）3Al5O12 decreased with the inerease of the ionic radii of the doping lanthanide ions （La^3＋： 0.106 nm, Gd^3＋： 0. 094 nm, Lu^3＋ ： 0.083 nm）. The bigger doping ion of Gd^3＋ made the emission of （Y0.96-xGdxCe0.04）3Al5O12 move to red spectral region, but the smaller one of Lu^3＋ made it blue.     

Behavior of leaching and precipitation of weathering crust ion-absorbed type by magnetic field

With weathering crust Ion-Absorbed Type Rare Earth （IATRE） ores in southern Jiangxi as an example, rare earth percolation leaching and leaching solution precipitation process research were carried out under conditions of magnetic field. The effect on the rare earth leaching process such as magnetic field strength, magnetization time, magnetization manner, and other factors were discussed. The effect on the mother rare earth liquor sedimentation rate, purity, and crystallization behavior such as magnetic field strength, magnetization time, and magnetization manner were investigated. Leaching and precipitation mechanism of magnetization on IATRE were analyzed. The results showed that the magnetic treatment can improve leaching rate of weathering crust IATRE and the sedimentation rate, and reduce consumption of reagents.     

Effect of ytterbium inclusion in hafnium oxide on the structural and electrical properties of the high-k gate dielectric

Abstract： The undoped and Yb-doped HfO2 thin films were deposited on p-type single crystal St（100） substrates using RF magnetron sputtering method. The structure and electrical properties were investigated as a function of doping concentrations. The results showed that the presence of Yb could stabilize HfO2 in cubic phase. The dielectric constant was enhanced after in- troducing Yb3＋ ions into the HfO2 host. Compared with undoped HfO2 thin film, the Yb-doped l-IfO2 thin film exhibited a low leakage current. The silicate reaction between rare earth ions and SiO2 layers was used to eliminate interfacial silica and form a stable interface.     

Spectroscopic properties of ytterbium doped KLu（WO_4）_2

Monoclinic Yb3+-doped KLu(WO4)2 (Yb:KLuW) crystal with large sizes was grown by top-seeded solution growth (TSSG) method. Room-temperature absorption and fluorescence spectra were measured. The ground-state energy-level splitting was 562 cm-1. The absorption cross section, peak emission cross section as well as the minimum inversion fraction ?min and the minimum absorbed pump intensity Imin were calculated. The measured emission lifetime was 0.676 ms and the emission spectral bandwidth (FWHM) was up to 55 nm. In comparison with established laser crystals the results suggested that this crystal has potential application in efficient tunable and femtosecond laser operation.     

Characterization,crystal structure and luminescence properties of a new europium（Ⅲ） complex with macrocyclic ligand derived from 2,6-diformyl-4-methylphenol and diethylenetriamine

The title compound （13,27-dimethyl-3,6,9,17,20,23-hexaazatricyclo-[23.3.1.1^11,15]-triaconta-1 （29）,2,9,11,13,15（30）, 16,23,25,27- decaene-29,30-diol-N^3, N^6, N^9, O^29, O^30）-bis （nitrato-O,O＇）-europium （Ⅲ） nitrate hydrate （[EuL（NO3）2]（NO3）·H2O, L denotes the macrocyclic ligand） was prepared and characterized by elemental analysis, infrared spectra, and electrospray mass spectra. Its crystal and molecular structure was determined by X-ray diffraction. The crystal crystallized in the monoclinic system, space group C2/c with a=2.3757 （4） nm, b=1.4302（3） nm, c=1.9584（3） nm, β=91.654（5）°, M=818.60, V=6.651（2） nm^3, Z=8, D=1.635 g/cm, F（000）=3312, R=0.0542, wR=0.1045. The central ion Eu^3＋ was nine-coordinated in the coordinaton geometry of a distorted tricapped trigonal prism. The macrocycle was coordinated through two oxygen and three nitrogen atoms. Two nitrate are chelate in the opposite positions of the macrocycle, the third nitrate being ionic. At room temperature, excitation of the title complex gave rise to the characteristic emissions of the Eu^3＋ ion.     

Solvent induced shape change in CePO4:Dy3+ nanophosphors and effect of metal ions:A photoluminescence study

The influence of different solvents and metal ions (Li+, Ba2+, Bi3+) on the crystallization behaviour, morphology and enhancement in photoluminescence intensity of Dy3+ doped CePO4 were investigated. Highly crystalline luminescent nanophosphors of CePO4:Dy3+ re-dispersible in polar solvents were successfully prepared via a simple polyol route at 140 ℃. As-prepared Dy3+ doped CePO4 nanophos-phors prepared in EG and DMF appeared to have crystalline monoclinic phase but exhibited hexagonal phase when prepared in water and water mixed solvents. The hexagonal phase transformed to monoclinic phase after heating at 900 ℃. TEM study revealed different shapes of the synthesized nanophosphors with change of solvents. The luminescence intensity of 4F9/2→6H15/2 at 478 nm (blue) was found to be more prominent than 4F9/2→6H13/2 at 572 nm (yellow). The introduction of metal ions (Li+, Ba2+ and Bi3+) in CePO4:Dy3+ led to considerable lumi-nescent enhancement. The nanophosphors were subsequently incorporated in polymer films of PVA which showed the characteristic emissions of Dy3+. It also served as an effective method to improve the performance of polymer materials and brought about novel properties in them.     

Luminescent properties and energy transfer of color-tunable Sr3Y2（SiO3）6：Ce3＋,Tb3＋ phosphors

Phosphors with controlled emission spectra are of great interest due to their application for white light emitting diodes.Herein, a new class of Sr3Y2（SiO3）6：Ce3＋,Tb3＋ phosphors were synthesized by a facile sol-gel combustion method. The phase structure,morphology, and luminescence properties of the phosphors were characterized by using powder X-ray diffraction（XRD）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, and photoluminescence excitation and emission spectra,respectively. The results on luminescence properties indicated that co-doped Ce3＋ ions served as UV-light sensitizers with excitation energy partially transferred to Tb3＋ ions, leading to green emission from Tb3＋. Particularly, the corresponding emitting colors of the phosphors could be well-tuned from deep blue（0.16, 0.05） to green region（0.25, 0.45） by adjusting the molar ratio of Ce3＋/Tb3＋.     

Monophthalocyanine complexes of samarium and terbium with axial ligands:synthesis,structure and optoelectronic properties

The monophthalocyanine complexes of samarium and terbium containing axial 2-mercaptobenzothiazole(Pc Sm(MBT)(1)), 2-(2-benzoxazol-2-yl) phenolate(Pc Tb(OON)(2)) or 2-(2-benzothiazol-2-yl)phenolate(Pc Tb(SON)(3)) ligands were synthesized and identified by elemental, LDI-TOF and X-ray(for 1) analysis.Photoluminescence(PL) and electroluminescence(EL) spectra of the compounds contained only emission bands of phthalocyanine and axial ligands but did not contain the bands of f-f transitions.It was found that among the complexes 1, 2, 3 the latter had highest photoconductivity(~10–7 S/cm) and photovoltaic properties.An organic photovoltaic device(OPV) of configuration of ITO/3/C60/Alq3/Al revealed open-circuit voltage(VOC) of 0.24 V and short current density(ISC) of 0.3 μA/cm2 under illumination by a xenon lamp at 17 m W/cm2.