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排序方式: 共有88条查询结果,搜索用时 15 毫秒
1.
In this paper for the first time, the compounds Y0.5 ? x Li1.5PO4:Eu x (YLP:Eu) were synthesized by the simple method of solid state reaction. The technology takes much time dry low temperature and little time calcined to synthesize rare earth phosphates. Their structures were analyzed by X-ray powder diffraction experiment. The excitation and emission spectra were measured at room temperature. Y0.5 ? x Li1.5PO4:Eu x shows the characteristice emissions of Eu3+ (5 D 0-7 F 1, 2, 3, 4 transitions dominated by 5 D 0-7 F 4). Incorporation of Li+ ions in the phosphors promote the crystallinity, reduce the amount of Y2O3, and lower the cost of production, moreover, transition dominated by 5 D 0-7 F 4 is important for a number of practical applications. 相似文献
2.
Xin-Yuan Sun Yun-Zhi Zhou Xiao-Guang Yu Hao-Hong Chen Hong Wang Zhi-Jun Zhang Xin-Xin Yang Jing-Tai Zhao 《Applied physics. B, Lasers and optics》2013,110(1):27-34
The BaGd2?x O4:xDy3+ (0 ≤ x ≤ 0.08) phosphors were synthesized at 1,300 °C in air by the solid-state reaction route. The as-synthesized phosphors were characterized by X-ray powder diffraction, photoluminescence excitation spectra, photoluminescence (PL) spectra, X-ray excited luminescence (XEL) spectra, and thermoluminescence (TL) spectra. It is found that the quenching concentration of Dy3+ ions in BaGd2O4 host is dependent on the selected excitation wavelength. The optimal PL intensity for the investigated BaGd2?x O4:xDy3+ phosphors is found to be x = 0.01, 0.02, and 0.04, upon excitation by 234, 277, and 350 nm ultraviolet light, respectively. The energy transfer among Dy3+ ions upon excitation by 350 nm is confirmed to be an electric dipole–dipole interaction mechanism based on the fitting of Huang’s rule. In addition, the intensive XEL from BaGd2O4:Dy3+ phosphor is observed by the naked eyes at room temperature, and TL properties of the investigated phosphors are analyzed and discussed. All the results imply that the investigated phosphors could be a promising scintillating phosphor. 相似文献
3.
采用双十八烷基-L-苯丙氨酸(Bis18-L-Phe)为凝胶因子,制备了具有热可逆性的十四酸异丙酯(IPM)超分子凝胶。IPM凝胶相转变温度(Tgel)随Bis18-L-Phe浓度增大而增加。偏光显微镜(POM)显示在整个IPM凝胶中形成了相互缠绕的针状聚集体。FT-IR光谱分析表明Bis18-L-Phe分子间酰胺的氢键作用是IPM凝胶形成的一个重要驱动力。IPM凝胶动力学研究表明凝胶时间随Bis18-L-Phe浓度的增大而缩短,随着温度升高而延长,因此IPM凝胶时间可以通过温度和Bis18-L-Phe浓度调控。 相似文献
4.
Xiaosong Tang 《Annali dell'Universita di Ferrara》2014,60(2):429-445
In this paper, we study the existence and uniqueness of a nontrivial solution to eigenvalue problems for the following nonlinear fractional differential equation of the form $$\begin{aligned} \left\{ \begin{array}{l} -D^{\alpha }_{0^{+}}u(t)=\lambda [f(t, u(t), D^{\beta }_{0^{+}}u(t))+g(t)],~~ 0 where \(\lambda \) is a parameter, \(D^{\alpha }_{0^{+}},D^{\beta }_{0^{+}}\) are two standard Riemann–Liouville fractional derivatives, \(0<\beta <1<\alpha \le 2,\alpha -\beta >1,f: [0,1]\times {\mathbb{R }}\times {\mathbb{R }}\rightarrow {\mathbb{R }}\) is continuous, and \(g(t): (0, 1)\rightarrow [0, +\infty )\) is Lebesgue integrable. We obtain several sufficient conditions of the existence and uniqueness of nontrivial solution of the above eigenvalue problems when \(\lambda \) is in some interval. Our approach is based on the Leray–Schauder nonlinear alternative. In addition, some examples are included to demonstrate the main result. 相似文献
5.
Optical spectra (absorption, emission, excitation, decay) and dielectric relaxation were measured for divalent europium and partially for ytterbium in lanthanum fluoride crystals. Optical absorption of LaF3–Eu2+ contains not only asymmetric weakly structured band at 245 nm but also less intense bands at 330, 380 nm. Broadband Eu2+ emission at 600 nm appeared below 80 K with decay time 2.2 μs at 7.5 K. Emission at 600 nm is attributed to so-called anomalous luminescence. Bulk conductivity is directly proportional to absorption coefficient of Eu2+ bands. Dielectric relaxation peak of LaF3–EuF3 is attributed to rotation of dipoles Eu2+-anion vacancy. The long-wavelength absorption at 300–400 nm region are assigned to transitions from 4f7Eu2+ ground state to states of neighbouring fluorine vacancy. 相似文献
6.
Ricerche di Matematica - In this paper, we investigate a mixed fractional integral boundary value problem with p(t)-Laplacian operator. Firstly, we derive the Green function through the direct... 相似文献
7.
8.
In this paper, we present the synthesis and luminescence properties of Tb3+ and Dy3+-doped lithium lutetium yttrium borate (Li6LuY(BO3)3) phosphors. We have adopted the well-known solid state reaction method for the synthesis of these phosphors. The emission intensities of the synthesized phosphors were found to reach their maximum, when doped by 1 mol% of Tb3+ and 3 mol% of Dy3+, beyond which emission intensities decrease due to concentration quenching. The homogeneous phase, crystalline structure and uniform morphology of the synthesized phosphors were confirmed by X-ray diffraction analysis (XRD) and Scanning electron microscopy (SEM). The X-ray and UV–VIS-induced luminescence, decay time and CIE chromaticity were investigated for the synthesized phosphors.The X-ray induced integrated light yield was measured to be 82% for Li6LuY(BO3)3:Tb3+ (LLYBO) and 59% for Li6LuY(BO3)3:Dy3+ of that of commercially available X-ray imaging material; Gd2O2S:Tb3+ (Gadox).LLYBO:Tb3+ phosphor displayed five major emission bands that correspond to 5Dj → 7Fj transitions. The 1931 Commission Internationale de l'Eclairage (CIE) chromaticity coordinates were also measured. 相似文献
9.
10.
《Tetrahedron letters》1987,28(48):5969-5972
The diphenylpropargyl cation has been shown to be a powerful Diels-Alder dienophile which adds to dienes in high yield at ambient temperatures. 相似文献