Photoluminescence,photo-stimulated luminescence and thermoluminescence properties of CaB2O4 crystals activated with Ce3+

Photoluminescence (PL), photo-stimulated luminescence (PSL), and thermoluminescence (TL) properties of a Ce-doped CaB₂O₄ crystal were studied. The Ce-doped crystal was prepared by the simple solidification method using a Pt crucible under nitrogen atmosphere. A PL emission band in the 350–370 nm wavelength range was obtained under excitation at 325 nm owing to the 5d (t_2g)–4f (²F_5/2, ²F_7/2)-allowed transition of the Ce³⁺ emission center. The fluorescence quantum efficiency and the decay time of Ce³⁺ were estimated to be about 70% and 29 ns, respectively. The 5d–4f emission band of Ce³⁺ also appeared in the 350–370 nm wavelength range in the TL and PSL spectra. Good linear TL and PSL responses were observed in the 1–1000 mGy and 1–10,000 mGy X-ray dose range, respectively.     

Synthesis and optical properties of sub-micron sized rare earth-doped zirconia particles

Sub-micron sized crystalline particles of Eu³⁺ and Er³⁺-doped zirconia (ZrO₂) were prepared via a wet chemical sol-gel route and post synthesis annealing. The doping was achieved by introduction of the respective rare earth salts into the zirconia precursor solution, with insitu generation of sodium chloride for stabilization of the particle surface during growth. A series of materials with differing europium content, nominally 0.3, 3 and 6 mol% within the ZrO₂ lattice, were prepared for respective comparison and characterization of their optical properties following annealing at 700 °C. Average emission lifetimes of up to 2.3 ms were observed for the Eu³⁺-doped particles. Particle sizes, approximated from SEM micrographs, were observed in the range 250-400 nm. The synthesis of Er³⁺-doped ZrO₂ particles (0.5 mol%) produced 300 nm sized particles which exhibited emission in the visible and infrared regions after annealing at 1000 °C. X-ray diffraction (XRD) with Rietveld analysis for phase quantification, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence (PL) spectra were used to characterize the samples.     

Preparation of Rare Earth Hydroxide and Oxide Nanoparticles by Precipitation Method

A series of rare earth hydroxide and oxide nanoparticles have been prepared by precipitation method with alcohol as the dispersive and protective reagent. Transmission electron microscope (TEEM) images indicate that the particles are spherical in shape and smaller than 100 nm in size. The crystallite sizes of cubic Ln2O3 have lanthanide shrinking effect, while average crystal lattice distortion rates possess lanthanide swelling effect. The diffraction peak intensity of heavy rare earth oxide nanometer powders is remarkably stronger than that of light rare earth oxide nanometer powders. The variation of diffraction intensity with atomic number presents an inverted W type, forming a double peak structure. Fourier transform infrared (FTIR) spectrums reveal that Ln2O3 nanopowders have higher surface activity than that of ordinary Ln2O3 powders. The UV-vis spectra show that Ln-O bond of these particles is slightly blue-shifted, and its absorption intensity decreases.     

Spectroscopic properties of Bi2ZnOB2O6 single crystals doped with Pr3+ ions: Absorption and luminescence investigations

Nonlinear optical Bi₂ZnOB₂O₆ single crystals doped with Pr³⁺ ions were grown using the Kyropoulos method. The absorption and luminescence properties of these new systems were investigated for the first time. The crystals are characterized by the large values of nonlinear optical coefficients. Effective luminescence of the Pr³⁺ ions makes this system an excellent candidate for the near-infrared (NIR) and/or ultraviolet (UV) to visible (VIS) laser converters. Based on the obtained experimental spectroscopic data, detailed analysis of the absorption and luminescence spectra was performed using the conventional Judd–Ofelt theory. Those transitions, which can be potentially used for laser applications of the Pr³⁺ ion, have been identified. In addition to the intensity parameters Ω₂, Ω₄, Ω₆ the branching ratios and radiative lifetimes were estimated for all possible transitions in the studied spectral region.     

Bright room-temperature green luminescence from YSZ:Tb

The room temperature spectroscopic properties of terbium doped zirconia fibres grown by Laser Floating Zone method are reported. The fibres were found to be stabilised in the tetragonal crystalline phase as measured by X-ray diffraction and Raman spectroscopy techniques. The doping with terbium ions was performed during the growth process and their incorporation on the wide band gap oxide host assumes an important role on the stabilisation of the high temperature tetragonal crystalline phase. Under ultraviolet optical pumping a bright green luminescence was observed by naked eye at room temperature, corresponding to the 4f → 4f transitions between the crystal-field split energy levels of the ⁵D₄ and ⁷F₅ manifolds of the 4f⁸ electronic configuration of the Tb³⁺ ions. These results suggest that YSZ:Tb³⁺ could be considered as a promising candidate for applications in green electroluminescent devices.     

溶胶-凝胶法制备铝酸锶发光材料

用溶胶 凝胶法合成制备铝酸锶 (SrAl2 O4:Eu2 + (SE) ,SrAl2 O4:Eu2 + ,Dy3+ (SED) )体系长余辉发光材料 ,用X射线粉晶衍射仪 (XRD)、荧光光度计等对制备产物进行了分析测试。用溶胶 凝胶法 (Sol gel)制备铝酸锶长余辉体的最佳温度为 1 2 0 0～ 1 2 5 0℃。     

Upconversion luminescence of holmium and ytterbium co-doped yttrium oxysulfide phosphor

The upconversion optical characteristic and brightness of Y₂O₂S:Yb,Ho phosphors are investigated. It is shown that Y₂O₂S:Yb,Ho exhibits NIR, red, green, blue and even ultraviolet-blue emission bands under 980 nm pumping. Moreover, Y₂O₂S:Yb,Ho shows excellent upconversion luminescence and its upconversion brightness is 2.2 times to that of the commercial Y₂O₂S:Yb,Er phosphors. The upconversion mechanism is discussed: the green and NIR emissions are due to two consecutive energy transfer from Yb³⁺ to Ho³⁺, and the blue and red emissions can be explained as a loop-like mechanism.     

Effects of calcination temperature and Li+ ions doping on structure and upconversion luminescence properties of TiO2:Ho3+-Yb3+ nanocrystals

Ho³⁺-Yb³⁺ co-doped and Ho³⁺-Yb³⁺-Li⁺ tri-doped TiO₂ nanocrystals were prepared using the sol-gel method. Effects of the calcination temperature and Li⁺ ions doping on the structure and upconversion luminescence properties of Ho³⁺-Yb³⁺ co-doped TiO₂ nanocrystals were investigated. The upconversion luminescence of nanocrystals was enhanced with the reduction of the crystal lattice symmetry and the crystallinity improvement of the matrix, which were facilitated by the calcination temperature change and Li⁺ ions doping. The lowest lattice symmetry and the best crystallinity of the matrix resulted in the maximum luminescence intensity.     

Up-conversion luminescence of trivalent-rare-earth ion-doped LnTaO4 (Ln = Y, Gd, La)

The up-conversion luminescence properties of trivalent-rare-earth ion-doped orthotantalates are studied under 980 nm laser diode excitation. The results indicate that YTaO₄:Tm³⁺/Yb³⁺ emits blue and strong infrared emissions respectively corresponding to ¹G₄→³H₆ and ³H₄→³H₆ transitions of Tm³⁺ ions, while YTaO₄:Er³⁺/Yb³⁺ produces strong green and weak red emissions, resulting from ²H_11/2/⁴S_3/2→⁴I_15/2 and ⁴F_9/2→⁴I_15/2 transitions of Er³⁺ ions, respectively. In contrast to three excellent up-conversion phosphors, viz. NaYF₄:Er³⁺/Yb³⁺, Y₂O₂S:Er³⁺/Yb³⁺ and Y₂O₃:Er³⁺, YTaO₄:Er³⁺/Yb³⁺ shows not only strong green emission, but also larger intensity ratio of green to red emission. In addition, it is found that LaTaO₄: Er³⁺/Yb³⁺ shows the minimum quenching concentration of Yb³⁺ and weakest up-conversion emission intensity, and the main peak presents blue shift (8 nm/556 nm) as compared with YTaO₄:Er³⁺/Yb³⁺ and GdTaO₄:Er³⁺/Yb³⁺. The distinct luminescent characteristics of LaTaO₄: Er³⁺/Yb³⁺ can be attributed to the larger difference of radius between doped ion and La³⁺ ion.     

Dual-mode luminescence from lanthanide tri-doped NaYF4 nanocrystals

Silica-coated NaYF₄:Yb/Er(Tm)/Eu nanocrystals (NCs) with a mean size of 35 nm were prepared and characterized. Each of the core/shell NCs can be dispersed in ethanol and water to form stable colloidal solutions and emit bright visible light of two colors (blue and red, green and red) by up- and down-converting excitation modes. As we know, this is the first time to obtain the distinct dual-color photos of NaYF₄:Yb/Er(Tm)/Eu NCs which were dispersed in deionized water. In particular, the ability to optically manipulate luminescence color of NCs doped with RE ions opens the door to multiplexed detection for high precision in more complex biotic environment.     

共沉淀法制备长余辉发光材料SrAl_2O_4:Eu~(2+),Dy~(3+)的研究

用共沉淀 (CST)法制备长余辉发光材料SrAl2 O4 :Eu2 + ,Dy3+ (SED) ,用红外光谱仪 (IR)、X射线粉晶衍射仪 (XRD)、荧光光度计对制备产物进行分析测试 ,确定了用共沉淀法制备SED长余辉体的最佳条件 ,其最佳灼烧温度为 110 0℃     

Temperature dependent luminescence in (Eu, Dy) doped tellurite glass

This short paper reports both the photoluminescence and the lifetime measurements of a prominent emission transition (⁵D₀→⁷F₂) of Eu³⁺ both in the presence and absence of the codopant rare earth ion (Dy³⁺) in an optical glass of the composition (79−x)TeO₂+6AlF₃+15LiF+xLn₂O₃ as a function of temperature down to 10 K.     

稀土在银基接触材料中的作用与应用

介绍了稀土在银及银合金电接触材料中的作用、特点及影响效果,阐述了国内外稀土银合金电接触材料的应用情况,展望了稀土银合金的发展前景。     

稀土发光材料Y2-x-yEuxLiyO3电荷补偿机制和发光机理研究

通过Li离子和发光离子共掺杂制备的稀土发光材料可以较大的提高样品的发光强度,本文通过密度泛函计算讨论这种材料中的电荷补偿形式,认为在较大浓度的情况下,对Li离子的电荷补偿主要以单独的间隙氧缺陷为主,间隙氧离子的引入,将会导致材料中出现掺杂能级。此外,基于试验结果,还对发光增强的机理进一步进行了讨论。     

Synthesis,spectroscopic and structural studies on YOF,LaOF and GdOF nanocrystals doped with Eu3+, synthesized via stearic acid method

Nanocrystalline Eu³⁺ doped REOF oxofluorides (where RE = Y, La, Gd) were synthesized using stearic acid as the reaction medium. Optimal conditions for the synthesis of pure and single-phased oxyfluorides were found. The obtained products were analysed using thermogravimetric analysis, X-ray analysis, transmission electron microscopy and the Rietveld method. The influence of calcination temperature on the physicochemical properties was studied. Spectroscopic properties of the tetragonal and rhombohedral oxyfluoride nanocrystals were investigated using excitation and emission spectra and luminescence lifetime measurements. Effectiveness of the Eu³⁺ dopant red emission intensity and energy transfer processes were examined in relation to the structure and the presence of the RE ion in oxyfluorides studied. The highest luminescence efficiency was observed for the GdOF:Eu³⁺ nanomaterial. Judd–Ofelt intensity parameters were calculated and analysed.     

A Comparison of Corrosion Behavior in Saline Environment: Rare Earth Metals (Y, Nd, Gd, Dy) for Alloying of Biodegradable Magnesium Alloys

Rare earth(RE) metals are widely used as the alloying elements in biodegradable magnesium alloys as medical implants.However,corrosion behavior of pure RE metals not only in physiological media but also in chlorinated saline environment is not well understood.In the present work,the RE metals Y,Nd,Gd and Dy are selected to investigate their corrosion behavior in 0.1 mol/L NaCl solution with immersion and electrochemistry techniques.As indicated,corrosion of the currently investigated RE metals is promoted in the order of Dy,Y,Gd and Nd.In terms of electrochemical response,such a sequence correlates with the increased impedance and the decreased corrosion rate(CR).These RE metals manifest weak ability for passivation in the native surface.Then,reaction with aqueous solution easily happens through the anodic dissolution and cathodic hydrogen evolution.The corrosion products,RE(OH)3,adhered on the surface of RE metals,do not have an appreciable power to resist the reaction proceeding with corrosive chloride ions.In contrast to pure Mg,the RE metals,including Y,Nd,Gd and Dy,exhibit significantly fragile corrosion resistance in saline media.Therefore,with the current findings,it is impossible to reveal a well-defined correlation of corrosion resistance between RE-containing Mg alloy and RE metal itself.     

The persistent energy transfer of Eu and Mn and the thermoluminescence properties of long-lasting phosphor Sr3MgSi2O8:Eu, Mn, Dy

Eu²⁺, Mn²⁺ and Dy³⁺ co-doped long-lasting phosphors Sr₃MgSi₂O₈ were prepared by a solid-state reaction under a reductive atmosphere. Fluorescence spectra demonstrated that the weak red emission resulting from the forbidden transition of Mn²⁺ could be enhanced by the energy transfer from Eu²⁺ to Mn²⁺. The energy transfer between Eu²⁺ and Mn²⁺ was systematically investigated. The phosphorescence spectra revealed that Eu²⁺ could persistently transfer its energy to Mn²⁺ after removing the excitation source. The duration of Mn²⁺ can prolong to more than 2 h. The thermoluminescence spectra were used to characterize the ability of the trap to trapping the carriers. By the analysis of the ionization potentials, the roles of Mn²⁺ and Dy³⁺ in the afterglow process were discussed. A possible afterglow mechanism was presented and discussed.