Journal of Alloys and Compounds
A solid solution with formula (Y1-xTbx)(3)GaO6 (x = 0-0.5) was prepared by solid-state reaction method. Powder X-ray diffraction (XRD) shows that Y3GaO6 is isostructural to Gd3GaO6 (Cmc2(1)), and the lattice parameters are a = 8.8364(1) angstrom, b = 11.0899(1) angstrom and c = 5.3937(1) angstrom. Atomic parameters were derived by Rietveld refinement of the XRD pattern. Photoluminescence (PL) spectra show a strong green emission of 543 nm from the D-5(4) -> F-7(5) transition of Th3+ at room and liquid nitrogen temperature. There is a wide saturation range of the PL intensity for the Th3+ content from x = 0.04-0.20, and a long life time about 1200 mu s for the green 543 nm emission at room temperature. (c) 2006 Elsevier B.V. All rights reserved.
关键词:
Y3GaO6;crystal structure;Tb3+ doped;photoluminescence;luminescence properties;dependence;y3al5o12;phosphor;ions;ce3+;tb-3;uv
Journal of Solid State Chemistry
The crystal structures of a series of compounds with the composition Ln(3)GaO(6)(Ln = Nd, Sm, Eu, Gd, Tb, Dy, Ho and Er) synthesized by solid-state reaction at 1400degreesC are investigated. X-ray diffraction shows that Ln3GaO6 has a non-centro symmetric orthorhombic structure (space group Cmc2(1)). Lattice parameters a, b, c and cell volume and the average distances between Ln(l)-O, Ln(2)-O of these compounds decrease with the decreasing of the radii of trivalent Ln ions, which accord with the expected lanthanide contraction behavior. There are two sites of seven-fold coordination for Ln atoms with oxygens, and Ga atoms are in oxygen tetrahedra which are distorted and elongated along the a-axis. Magnetization measurements indicate that the susceptibility X changes with temperature in Curie-type manner. (C) 2004 Elsevier Inc. All rights reserved.
关键词:
Ln(3)GaO(6);crystal structure;Rietveld refinement;X-ray diffraction;garnets
Journal of Luminescence
Ln(3+) (Ln = Nd, Sm, Eu, Gd, Dy, Ho, Er)-doped Y3GaO6 compounds were prepared by solid-state reaction, and their optical spectra such as absorption, photoluminescence, excitation and time-resolved spectra have been measured for Ln Nd, Sm, Dy, Ho, Er. X-ray powder diffraction shows that the lattice parameters of the compounds (Y(0.96)Ln(0.04))(3)GaO6 decrease with the decrease of the radii of trivalent Ln(3+) ions, indicating that Ln(3+) ions have substituted for y(3+) ions in the lattice. Optical spectra show that there are obvious absorptions at ultraviolet to visible region. The strong emissions in visible and infra-red region show that Y3GaO6 is a suitable host for rare-earth-doped laser crystal and phosphor materials. (C) 2004 Elsevier B.V. All rights reserved.
关键词:
crystal-field;absorption-spectra;luminescence;y3ga5o12;glasses;garnet;y2o3;ions;laf3;tb3
Journal of Solid State Chemistry
A serial of samples in Y2O3-Ga2O3-Tm2O3 pseudo-ternary system are prepared by solid-state chemical reaction method. The range of solid solution in (Y1-xTmx)(3)GaO6 is 0 < x < 0.384. Powder X-ray diffraction shows that the compounds crystallize in Gd3GaO6 (Cmc2(1))-type structure. The solid solubilities of Y3+xGa5-xO12 (x = 0-0.77) and Tm3+xGa5-xO12 (x = 0-0.62) are 37.5-47.11 at% Y2O3, and 37.5-45.26 at% Tm2O3, respectively. PL spectra of Tm-doped Y3GaO6 show that there is a sharp blue emission at similar to 456 nm from the D-1(2) -> F-3(4) transition at room temperatures with two lifetimes (similar to 5 and similar to 15 mu s) and a narrow saturation range of PL intensity for the Tm3+ content from x = 0.005 to 0.03. The sharp emission and long lifetime of (Y1-xTmx)(3)GaO6 indicate that Y3GaO6 is a potential phosphor and laser crystal host material. (c) 2005 Elsevier Inc. All rights reserved.
关键词:
Tm3+ -doped Y3GaO6;Y2O3-Ga2O3-Tm2O3 system;(Y1-xTmx)(3)Ga5O12 solid;solution;luminescence;crystal-structure;luminescence;phosphor;cations;ions;tb3
张兰河
,
李德生
,
王旭明
,
张海丰
硅酸盐通报
为了提高生物除磷效率,研究采用AOA-SBR工艺进行了长期连续除磷实验,考察不同温度下碳源(乙酸钠、丙酸钠、葡萄糖)对PAO与GAO竞争的影响.结果表明:当温度由10℃升高至25℃时,利用丙酸钠作为碳源时,污泥含磷量与含糖量分别从7.2％和5.1％升高至7.9％和6.3％,PHA转化量升高了23.1 mg/L,厌氧释磷量从105.9 mg/L升高至149.9 mg/L,VSS/MLSS由71％降低至65％;利用乙酸钠作为碳源时,污泥含磷量与含糖量分别从6.9％和5.3％升高至7.6％和6.7％,PHA转化量升高了23.9 mg/L,厌氧释磷量从73.8 mg/L升高至108.8 mg/L,VSS/MLSS由73％降低至71％;利用葡萄糖作为碳源时,污泥含磷量与含糖量分别从5.8％和6.3％升高至6.6％和8.8％,PHA转化量升高了33.2 mg/L,厌氧释磷量从37.4 mg/L升高至43.2 mg/L,VSS/MLSS由80％升高至88％.当温度升高至30℃时,3个反应器均出现厌氧末期PHA浓度下降和糖原浓度升高,厌氧释磷量减少,污泥含磷量均下降,污泥含糖量上升,VSS/MLSS均很高.与葡萄糖相比,采用乙酸钠和丙酸钠作为碳源,有利于PAO生长繁殖,PAO为优势菌种,抑制GAO增殖.同时,低温更有利于PAO的生长繁殖.
关键词:
温度
,
碳源
,
SBR
,
PAO与GAO
程开甲
,
程漱玉
稀有金属材料与工程
应用Cheng-Born能带对称破缺理论和TFDC(Thomas-Fermi-Dirac-Cheng)电子理论研究了薄膜层内电子的特性.对金属铂上的TiO2膜层来说,TFDC理论指出电子(或空穴)将由金属与膜的间界面一侧迁移到另一侧.根据Cheng-Born对称破缺理论,当能带中只有很少的电子时,则只有极少的角区中存在电子,动量空间即产生对称破缺,从而导致超导电性,并由热力学估算出薄膜超导体的转变温度.结果显示薄膜超导体的转变温度至少比块材超导体的转变温度高一个量级.作者还设计了一个研究薄膜超导电性的实验.
关键词:
超导电性
,
薄膜
,
对称破缺
,
TFDC
