Effects of Yb^3＋ codoping on visible and near infrared emissions of Er^3＋-Yb^3＋ codoped Al2O3 powders by the sol-gel method

The 0.1 mol% Er^3＋ and 0-2 mol% Yb^3＋ codoped Al2O3 powders were prepared by the sol-gel method, and the phase structure, including only two crystalline types of doped Al2O3 phase, γ-（Al,Er, Yb）2O3 and θ-（Al,Er, Yb）2O3, was detected at the sintering temperature of 1000℃. The visible and near infrared emissions properties depended strongly on the Yb^3＋ codoping, and the corresponding maximal peak intensities centered at about 523, 545, 660 and 1533 nm were obtained respectively for the 0.1 mol% Er^3＋ and 0.5 mol% Yb^3＋ codoped Al2O3 powders, which were composed of θ-（Al,Er,Yb）2O3 and a small amount of γ-（Al,Er, Yb）2O3 phases. The two-photon absorption process was responsible for the visible up-conversion emissions, and the one-photon absorption process was involved in the near infrared emissions of the Er^3＋-yb^3＋ codoped Al2O3 powders.     

Near-infrared to visible up-conversion emissions of Er^3＋ doped Al2O3 powders derived from the sol-gel method

The Er3 doped Al2O3 powders were prepared by the sol-gel method using the aluminium isopropoxide [Al(OC3H7)3]-derived Al2O3 sols with addition of the erbium nitrate [Er(NO3)3.5H2O]. The different phase structure, including three crystalline types of (Al,Er)2O3 phases, γ, θ, α, and two Er-Al-O phases, ErAlO3 and Al10Er6O24, was obtained with the 1 mol% Er3 doped Al2O3 powders at the different sintering temperatures of 600―1200℃. The green and red up-conversion emissions centered at about 523, 545 and 660 nm, corresponding respectively to the 2H11/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 transitions of Er3 , were detected by a 978 nm semiconductor laser diodes excitation. The phase structure and OH content had evident influence on the up-conversion emissions intensity. The maximum intensities of both the green and red emissions were obtained respectively for the Er3 doped Al2O3 powders sintered at 1200 ℃, which was composed mainly of α-(Al,Er)2O3, less of ErAlO3 and Al10Er6O24 phases, and with the least OH content. The two-photon absorption up-conversion process was involved in the green and red up-conversion emissions of the Er3 doped Al2O3 powders.     

直流电弧放电法制备Er^3＋-Yb^3＋：Al2O3纳米粒子的上转换发光特性研究

采用直流电弧放电法成功制备了粒度约60nm的Er^3＋-Yb^3＋共掺杂Al2O3纳米粒子.通过978nm激光二极管（LD）激发,获得位于526,547nm的绿色和677nm的红色上转换发光,分别对应于Er3＋的2H11/2→^4 I15/2,^4 S3/2→^4 I15/2和^4 F9/2→^4 I15/2跃迁.退火对于样品的上转换发光具有较大影响：退火前,红色发光明显,退火后则以绿色发光为主.（ErYb）3Al5O12和α-（Al,Er,Yb）2O3混合相中增强的激发态吸收^4I11/2＋光子→^4F7/2和能量传递^2F5/2（Yb^3＋）＋^4I11/2（Er^3＋）→^2F7/2（Yb^3＋）＋^4F7/2（Er^3＋）过程导致绿色上转换发光显著增加.绿色和红色上转换发光过程均为双光子上转换吸收.结果表明直流电弧放电法是一种极具发展潜力的光学材料制备方法.     

Study on relaxation oscillation of Er^3＋/Yb^3＋ co-doped phosphate glass optical waveguide laser

Based on the principle and fabrication of the optical waveguide laser, and through the configuration of the energy level of Er^3＋/Yb^3＋. co-doped system, the time-dependent rate equations are formed and then solved by Runge-Kutta algorithm. The dynamic characteristic of the waveguide laser pumped unidirectionally by 980 nm LD is analyzed. The curves of the relaxation oscillation are drawn, showing that the photon number and inverted population vary alternately. The attenuation characteristic of the peak power is studied. It is gained that time constant changes with pump power, length of waveguide and the reflectivity of output mirror. Furthermore, the impact of the above three parameters on the frequency and end-time of relaxation oscillation is discussed. The frequency of relaxation oscillation is proportional to the pump power. Under high reflectivity conditions, the length of waveguide has a weak impact on the frequency. The end-time decreases as the three parameters increase. These features and results provide a theoretical basis for designing the Er^3＋/Yb63＋. co-doped phosphate optical waveguide laser.     

Er^3＋/Yb^3＋共掺杂DFB光纤激光器的输出特性

介绍了Er^3＋/Yb^3＋共掺杂的能级模型,分析了Er^3＋和Yb^3＋之间能量传递的过程,在此基础上引入传输矩阵的模型,在计算Er3＋离子转换率的基础上,模拟了Er^3＋/Yb^3＋共掺杂DFB光纤激光器的输出特性,并且比较了泵浦光功率、损耗和光纤光栅长度对激光器输出功率的影响。     

Structure of aqueous sodium sulfate solutions derived from X-ray diffraction

A rapid liquid X-ray diffractometer was used to study the time-averaged and space-averaged structure of aqueous sodium sulfate solutions at 298 and 323 K. Difference radial distribution functions of the solutions were obtained from accurate diffraction data. The interaction distances of Na^＋-OH2 and S-H2O in solutions were found to be 0.235 and 0.385 nm, respectively, after deconvolution of superposition peaks by Gaussian multi-peak fitting program. The characteristic distance of the NaSO; contact ion pairs in higher concentration solutions was determined to be 0.345 nm, suggesting that the Na^＋ ions coordinated with SO4^2- ions in the mono-dentate form. Effects of concentration and temperature on the hydration structure of the solutions were discussed in the present paper. With a decrease in concentration, the contributions of the H2O to the diffraction pattern increase, the average coordination number of the Na^＋ ions hardly changes, while the hydration number of SO4^2- ions increases slightly. The formation of NaSO; contact ion pairs becomes easier at higher temperature. The structure of hydrogen bond in dilute solutions is broken to a considerable extent with rising temperature, and the peak at 0.290 nm splits into two peaks at 0.275 and 0.305 nm, respectively.     

Novel trichromatic phosphor Co-doped with Eu, Tb in SiO2 gel matrix

The Eu, Tb co-doped SiO2 matrix tricolor fluorescence system was prepared by sol-gel technique. Red emission at 618 nm, green emission at 543 nm and blue emission at 350-500 nm were observed in the PL spectra of the sample, indicating that Eu^3＋, Eu^2＋ and Tb^3＋ ions coexisted in the matrix. In the co-doped sample, the blue emission of Eu^2＋ was much stronger than that of the sample single doped with Eu, which implied that the electron transfer between Eu^3＋ and Tb^3＋ maybe happened in the SiO2 matrix. The influences of the annealing temperature and Tb concentration on the PL spectra of the samples were investigated. The optimal doped concentration of Tb was determined to be 0.2% and the optimal annealing temperature 850℃. Annealed at 600℃, Tb^3＋ had a sensitizing effect on Eu^3＋ in the SiO2 matrix, and the emission intensity of Eu^3＋ in the Eu, Tb co-doped sample was more than four times that of the single doped sample, which could be attributed to the energy transfer from Tb^3＋ to Eu^3＋.     

Ammonium record over the last 96 years from the muztagata glacier in Central Asia

As a major alkaline gas in the atmosphere, ammonia （NH3） plays an important role in atmospheric chemistry. However, there is little knowledge about NH3 variations in the Central Asia. Here we analyzed the ammonium （NH4^＋） history recorded in an ice core from the East Pamir in Central Asia, which was drilled on the Mt. Muztagata at the elevation of 7010 m a.s.I, in 2003. The core was carefully dated and NH; concentration history during 1907-2002 was reconstructed. The result shows that NH; concentration remained approximately constant until the 1930s after a sudden decrease at the very beginning of the 20th century, followed by a minimum in 1940 before increasing steadily to the peak at the end of 1990s. It is found that the annual mean NH4^＋ concentration was strongly associated with the Northern Hemisphere temperature, suggesting the impact of temperature on NH3 emissions in the Central Asia. Moreover, an increase of NH4^＋ concentration after 1940 also reflects the enhancement of NH3 emissions from anthropogenic sources such as fertilizer applications and livestock wastes in the 20th century.     

Tricolor white emitting phosphor co-doped with Eu, Dy in SiO2 matrix

A Eu, Dy co-doped SiO2 matrix, white emitting phosphor was prepared by the sol-gel technique. Strong red, green and blue emissions located at 618 nm, 573 nm and 400-550 nm were observed under UV laser excitation at room temperature. Such techniques as FT-IR and TGA-DSC were used to measure the microstructure of the luminescent material. The influence of the preparation techniques on the luminescence property of the Eu, Dy co-doped SiO2 matrix, such as anneal temperature, anneal time, dried atmosphere and the components of the matrix, was systematically studied, and the luminescence mechanism was interpreted. The red emission is the strongest when annealed at 750℃. However, blue emission appears when annealed at 700℃ and is the intensest at 900℃. For the samples dried in vacuum, Eu^3＋ is more easily deoxidized to Eu^2＋ at lower temperatures, because the samples dried in the air compared with that dried in vacuum need higher temperature to form network structures. Only the SA and SAB matrix annealed at 850℃ had blue emission in the four matrices （SA, SAB, SB, S） xerogel and the emission in the SAB matrix was stronger than that in the SA matrix. This may be due to the eutectic phase formed by the oxide boron, alkaline oxide and alumina in the SAB matrix, which constructs network structures and stabilizes the emission center and enhances the blue emission.     

Heat and hyposmotic stimulation increase in [Ca^2＋]i by Ca^2＋ influx in rat synoviocytes

Rheumatoid arthritis （RA）, which is marked by inflammatory synovitis, is a common, chronic autoimmune-disease, whose pathogenesis is complex and still unclear. In order to explore the effects of heat and hyposmotic stimuli on synoviocytes in rheumatoid arthritis, the changes of [Ca^2＋]i induced by heat, hyposmotic and 4α-PDD stimuli were observed in synoviocytes. [Ca^2＋]i elevation induced by heat 28℃, hyposmotic and 4α-PDD stimuli is found to be positively relative to increasing temperature, decreasing osmolality and rising concentration of 4α-PDD. Results show that there is reciprocity among these stimuli and desensitization, and that [Ca^2＋]i elevation depends on Ca^2＋ influx, but not necessarily links to Ca^2＋ release from intracellular stores and voltage-dependent Ca^2＋ channel in synoviocytes. The above characteristics of Ca^2＋ influx are similar to those of TRPV4. A probable mechanism has been suggested that heat and hyposmotic stimulation might increase the level of [Ca^2＋]i by activating the TRPV4-like channel and Ca^2＋ influx in the synoviocytes.     

Preparation and upconversion luminescence of YVO<Subscript>4</Subscript>:Er<Subscript>3+</Subscript>, Yb<Subscript>3+</Subscript>

YVO₄:Er³⁺, Yb³⁺ with varying Yb³⁺ concentrations were prepared by a precipitation method. The results of X-ray diffraction (XRD) show that all the samples have a tetragonal zircon structure; the calculated average crystallite sizes are in the range of 14–22 nm. The lattice constants and cell volume of the samples decrease slightly with the increase in Yb³⁺ concentration. The upconversion luminescence spectra of all the samples were studied under 980 nm laser excitation. The strong green emission is observed, which is attributed to the ²H_11/2 → ⁴I_15/2 and ⁴S_3/2→⁴I_15/2 transitions of Er³⁺, and the red emission peaks in 650–675 nm can be ignored. The emission intensity for the sample depends on the Yb³⁺ concentration. These results reveal that the upconversion processes of YVO₄:Er³⁺, Yb³⁺ are related to the structure and the doping Yb³⁺ concentration of the sample.     

Photoluminescence and cathodoluminescence properties of CaLaGa<Subscript>3</Subscript>O<Subscript>7</Subscript>:Eu<Superscript>3+</Superscript> phosphors

The CaLaGa₃O₇:Eu³⁺ phosphor was prepared by a chemical co-precipitation method. Field emission scanning electron microscopy (FE-SEM), laser particle size analysis, X-ray diffraction (XRD), photoluminescence (PL), and cathodoluminescence (CL) spectra were utilized to characterize the synthesized phosphor. The results revealed that the phosphor was composed of microspheres with a slight agglomerate phenomenon and was spherically shaped. The average grain size was about 1.0 μm. Eu³⁺ ions, as luminescent centers, substituted La³⁺ ions into the single crystal lattice of CaLaGa₃O₇ with the sites of C_s. Although the CL spectrum was greatly different from the PL spectrum, it had the strongest red emission corresponding to the ⁵D₀ →⁷F₂ transition of Eu³⁺. Under the excitation of UV light (287 nm) and electron beams (1.0–7.0 kV), the chromaticity coordinates of the phosphor were found to be in the nearly red and orange light regions, respectively.     

Photoluminescence and cathodoluminescence properties of a novel CaLaGa307：Dy3＋ phosphor

A single host white emitting phosphor, CaLaGa3O7:Dy3+, was synthesized by chemical co-precipitation. Field emission scanning electron microscopy, X-ray diffraction, laser particle size analysis, and photoluminescence and cathodoluminescence spectra were used to investigate the structural and optical properties of the phosphor. The phosphor particles were composed of microspheres with a slight tendency to agglomerate, and an average diameter was of about 1.0 μm. The Dy3+ ions acted as luminescent centers, and substituted La3+ ions in the single crystal lattice of CaLaGa3O7 where they were located in Cs sites. Under excitation with ultraviolet light and a low voltage electron beam, the CaLaGa3O7:Dy3+ phosphor exhibited the characteristic emission of Dy3+ (4F9/2-6H15/2 and 4F9/2-6H13/2 transitions) with intense yellow emission at about 573 nm. The chromaticity coordinates for the phosphor were in the white region. The relevant luminescence mechanisms of the phosphor are investigated. This phosphor may be applied in both field emission displays and white light-emitting diodes.     

Preparation and luminescence characteristics of Sr3SiO5：Eu^2＋ phosphor for white LED

The Sr3SiO5：Eu^2＋ phosphor was synthesized by high temperature solid-state reaction. The emission spectrum of Sr3SiO5：Eu^2＋ shows two bands centered at 487 and 575 nm, which well agree with the theoretic values of emission spectrum. The excitation spectrum for 575 nm emission center has several excitation bands at 365, 418, 458 and 473 nm. And the results show that the emission spectrum of Sr3SiO5：Eu^2＋ is influenced by the Eu^2＋ concentration. The relative emission spectra of the white-emitting InGaN-based YAG：Ce^3＋ LED and Sr3SiO5：Eu^2＋ LED were investigated. The results show that the color development of InGaN-based Sr3SiO5：Eu^2＋ is better than that of InGaN-based YAG：Ce^3＋, and the CIE chromaticity of InGaN-based Sr3SiO5：Eu^2＋ is （x=0.348, y=0.326）.     

Structural investigation and luminescent properties of BaZr(BO<Subscript>3</Subscript>)2:Eu<Superscript>3+</Superscript> phosphors containing Si

Si⁴⁺-doped BaZr(BO₃)₂:Eu³⁺ phosphors are prepared by a conventional solid-state reaction. The influence of Si⁴⁺ addition on the charge transfer state of Eu³⁺-O^2– and photoluminescence (PL) properties of BaZr(BO₃)₂:Eu³⁺ are discussed. Room temperature PL spectra indicated that efficient emission is obtained by Si doping. Increased values for the peak-peak ratio (PPR) of BaZr(BO₃)₂:Eu³⁺ at higher Si doping concentrations implied that the Eu³⁺ ion is located in a more asymmetric environment in BaZr_0.8Si_0.2(BO₃)₂:Eu³⁺ than in the undoped samples. The Judd-Ofelt parameters Ω_λ (λ=2,4) were calculated from the PL data, giving results that were consistent with those from the PPR. The maximum radiative quantum efficiency was achieved at a Si doping concentration of 20 mol%.     

Effects of ytterbium on outward K<Superscript>+</Superscript> currents in NIH3T3 cell

Using the whole cell patch-clamp technique, we observed the outward K+ currents and studied for the first time the effects of Yb3+ on the currents and kinetics of activation and inactivation in non-excitable NIH3T3 cell. Our results show that the outward K+ currents were promoted with increasing concentration of Ca2+ in pipette solution and saturated at the concentration of 100 μmol/L Ca2+. Yb3+ in bath solution inhibited the currents in a concentration-dependent manner. At the concentration of 1 μmol/L, Yb...     

PbxNayYzF2x+y+3z+3m∶Erm3+上转换发光粉的低温燃烧合成及表征

采用低温燃烧合成（LCS）法一步合成了Pb_xNa_yY_zF_2x+y+3z+3m:Er_m3+氟化物体系1 550 nm响应的红外上转换发光材料. 通过正交实验研究了4种阳离子影响发光性能的主次关系及最佳配比,研究了燃料用量对晶相形成及上转换发光性能的影响. 采用X射线粉末衍射仪、透射电镜、荧光分光光度计（耦合1 550 nm激光器）等手段对样品的物相、形貌及发光性能进行了测试与表征. 结果表明:阳离子含量对红光发射强度影响的主次关系为Y3+,Pb2+,Na+,Er3+,最佳配比为Pb_0.004Na_0.003 Y_0.003 F_0.032:Er3+_0.004. 燃料取2.5倍理论用量时样品的结晶度和发光强度最高.      

He-H2 mixture and Er3NiHx packing for the refrigeration enhancement of pulse tube refrigerator

The computation with the theory of modified Brayton Cycle indicates that higher cooling power and coefficient of performance for a pulse tube refrigerator can be achieved with He-H2 mixture as working gas than those with pure He in the temperature region of 30 K. In addition, it is found that Er3Ni, a regenerative material, is able to absorb H2 and produces Er3NiHx. The computation presents that the regenerative performance of Er3NiHx is better than that of Er3Ni due to its higher volume specific heat. Experimental results show that the pulse tube refrigeration performance in 30 K temperature region is enhanced greatly with He-H2 mixture and Er3NiHx packing.