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21.
22.
G. Teowee J. M. Boulton C. D. Baertlein R. K. Wade D. R. Uhlmann 《Journal of Sol-Gel Science and Technology》1994,2(1-3):623-626
A series of monolithic Pt-PZT-Pt capacitors was prepared based on sol-gel derived PZT 53/47 films fired to 700 C. After deposition of top Pt electrodes, the capacitors were subjected to post-metallization annealing (PMA) temperatures of 100 C to 700 C. Dielectric and ferroelectric (FE) characterizations were performed. Increasing the PMA temperature produced lower values of spontaneous and remanent polarizations, dielectric constant and leakage currents. The observations are correlated with a proposed FE capacitor model. 相似文献
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24.
Summary Samples of synthetic leucite and boron-substituted leucite are investigated by infrared spectroscopy and spectrally resolved
thermoluminescence. Evidence is obtained in favour of the assumption that point defects in aluminosilicate lattices are originated
by exchanges of Si+4 and Al+3 ions lying in different cells. 相似文献
25.
S. Burachas S. Beloglovsky D. Elizarov I. Makov Yu. Saveliev N. Vassilieva M. Ippolitov V. Manko S. Nikulin A. Nyanin A. Vasiliev A. Apanasenko G. Tamulaitis 《Radiation measurements》2004,38(4-6):367-370
Technological conditions ensuring growth of optically homogeneous lead tungstate (PWO) crystals are reported. It is shown that the basic scintillator characteristics of PWO grown from highly purified raw material and properly doped with lanthanides are mainly determined by inclusions of oxides W1−yLyO3−x (L=Y, La, Gd; 0<x<0.3). Moreover, surface-located inclusions with structure close to tungstenite may also be of importance. It is demonstrated that the scintillation properties can be intentionally designed by varying the oxygen content in the inclusions x and the surface structure. The optimal value for x and the most favorable surface structure are achieved by proper thermal regimes and environment content during the crystal annealing. The results enabled low-cost fabrication of PWO scintillators with steady and reproducible characteristics acceptable for the CERN project ALICE and ensured production of PWO on an industrial scale by “North Crystals” company at a rate of 125–135 crystals per year from every growth apparatus. 相似文献
26.
The thermally stimulated properties of PbWO4 in the temperature range 90–400 K have been investigated on undoped and terbium-doped crystals after X-ray irradiation at 90 K. Doping with terbium changes the concentration of shallow traps, which are responsible for retrapping free electrons and holes. Light illumination can change the distribution of the traps. The optically stimulated luminescence is observed. The influence of light illumination on the TSL curves and emission properties is studied. The possible mechanism of TSL phototransformation is discussed. 相似文献
27.
The field of photonic crystals has, over the past few years, received dramatically increased attention. Photonic crystals are artificially engineered structures that exhibit a periodic variation in one, two, or three dimensions of the dielectric constant, with a period of the order of the pertinent light wavelength. Such structures in three dimensions should exhibit properties similar to solid-state electronic crystals, such as bandgaps, in other words wavelength regions where light cannot propagate in any direction. By introducing defects into the periodic arrangement, the photonic crystals exhibit properties analogous to those of solid-state crystals. The basic feature of a photonic bandgap was indeed experimentally demonstrated in the beginning of the 1990s, and sparked a large interest in, and in many ways revitalized, photonics research. There are several reasons for this attention. One is that photonic crystals, in their own right, offer a proliferation of challenging research tasks, involving a multitude of disciplines, such as electromagnetic theory, nanofabrication, semi-conductor technology, materials science, biotechnology, to name a few. Another reason is given by the somewhat more down-to-earth expectations that photonics crystals will create unique opportunities for novel devices and applications, and contribute to solving some of the issues that have plagued photonics such as large physical sizes, comparatively low functionality, and high costs. Herein, we will treat some basics of photonic crystal structures and discuss the state-of-the-art in fabrication as well give some examples of devices with unique properties, due to the use of photonic crystals. We will also point out some of the problems that still remain to be solved, and give a view on where photonic crystals currently stand. 相似文献
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本文研究了H_2O_2氧化光泽精发光反应及乙醇的敏化作用,发现加入乙醇可使铅催化H_2O_2,氧化光泽精的发光强度有较大幅度的增强;铅量在3×10 ̄(-7)~8×10 ̄(-5)g/mL。范围内与发光强度成正比.方法检出限为0.10μg/mL;对含4μg/mLPb(Ⅱ)11次重复测定,其RSD为2.3%.对32种常见的阴阳离子进行了干扰实验,表明方法具有较好的选择性。本法应用于水样及沉积物标样中痕量铅的测定,结果良好。 相似文献
30.
Summary The nematic planar anchoring is usually explained by using simple elastic models: the surface easy axis corresponds to the
surface direction that minimizes the excess of nematic elastic energy. When anisotropic rough substrates are used to align
nematic liquid crystals, due to the complex surface morphology, usual elastic models are not directly applicable. This paper
presents quantitative topographical data of rough substrates, obtained with oblique SiO evaporation under vacuum for nematic
planar anchoring. Experimental data are obtained by means of Atomic Force Microscopy and they are used to demonstrate the
self-affine nature of these substrates and to relate the nematic anchoring with the anisotropy of the local fractal properties
of the substrate itself.
Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994. 相似文献