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Stefanie Kaesche Peter Majewski Fritz Aldinger 《Journal of Electronic Materials》1995,24(12):1829-1834
For the nominal composition of Bi2.27−xPbxSr2Ca2Cu3O10+d, the lead content was varied from x < 0.05 to 0.45. The compositions were examined between 800 and 890‡C which is supposed
to be the temperatue range over which the so-called 2223 phase (Bi2Sr2Ca2Cu3O10+d) is stable. Only compositions between x < 0.18 to 0.36 could be synthezised in a single phase state. For x <0.36, a lead-containing
phase with a stoichiometry of Pb4(Sr,Ca)5CuOd with a small solubiliy of Bi is formed, for x > 0.18 mainly Bi2Sr2CaCu2O8+d and cuprates are the equilibrium phases. The temperature range for the 2223 phase was found to be 800 to 890‡C but the 2223
phase has extremely varying cation ratios over this temperaure range. Former single phase 2223 samples turn to multiphase
samples when annealed at slightly higher or lower temperaures. A decrease in the Pb solubility with increasing as well as
decreasing temperature with a maximum at about 850‡C was found for the 2223 phase. 相似文献
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Magnetization measurements were carried out on bulk Tl2Ba2CaCu2O8 (referred to as Tl-2212) and on various site-selective substituted Tl-2212 samples. At 5K between 0 and 4.5 T, the 5 at.
% Mg-doped Tl-2212 (Tl,Mg-2212) samples displayed enhanced pinning as demonstrated by a field dependent increase of the magnetic
critical-current density Jc by 18 to 25 percent over that of pristine Tl-2212. Excess Mg (10–15 at. %), however, is deleterious. Rietveld refinement
of the x-ray diffraction pattern showed Mg on the Tl sites. Auger electron spectroscopy analysis showed part of the Mg on
grain boundaries. The flux-creep activation energies are higher for flux expulsion than for flux penetration in both Tl-2212
and Tl,Mg-2212 samples; the latter displays higher individual values. Our results demonstrate an increase in the number density
of flux lines as a result of increased density of atomic-size-structural, defects by Mg (5 at. %) doping. In the Tl2−yBa2(Ca1−zYz)Cu2O8−x(z=0–0.3; single phase; x and y represent oxygen and thallium vacancies) system also studied, the Tc decreases as z increases. At z=0.3, the sample becomes an antiferromagnetic semiconductor. 相似文献
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介绍激光焊接技术的发展历史,阐明激光焊接的发展与应用现状及未来的发展前景,论述激光焊接工艺的特点及需进一步研究与探讨的问题,将激光焊接(LBW)与电子束焊接(EBW)、惰性和活性气体保护电弧焊(GTAW和GMAW)及电阻焊(RW)工艺进行了全面的对比,指出激光焊接工艺的优势所在及其存在的问题。 相似文献
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激光熔覆硬质合金WC-TiN-Co特性的研究 总被引:3,自引:1,他引:2
本文介绍大功率CO2激光束在45钢表面涂敷WC-TiN-Co,进行了激光熔覆处理,对处理后样品的显微组织、物相、硬度分布和耐磨性能进行了测试和分析,结果表明:45钢表面的化学成分和显微组织发生了根本性的变化,硬度和耐磨性得到了很大提高。 相似文献
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V. Pavate L. B. Williams E. P. Kvam C. Varanasi P. J. Mc Ginn 《Journal of Electronic Materials》1994,23(11):1131-1134
Transmission electron microscopy examinations have been conducted on undoped and PtO2 doped YBa2Cu3O7−δ, with excess Y2BaCuO5 (211) in the molar ratio of 5∶1 (123/211), processing using the solid liquid melt growth technique. Magnetization hysteresis
suggests that addition of Pt strongly influences the pinning behavior. Considerable differences in dislocation and stacking
fault densities were observed. Dislocation nets and tangles were commonly observed in the Pt doped samples. In both samples,
stacking faults were observed near 211 precipitates, interplatelet boundaries, and dislocations. Dislocations appear to be
formed during high temperature processing, while stacking faults appear to be generated during the final oxygenation step.
The density and distribution of fine precipitates (∼25–100 nm) were comparable in both specimens suggesting that Pt additon
affects the size and acicular morphology of only the coarser 211 (∼1–10 μm). It is proposed that the observed increase in
Jc due to Pt addtion may be attributed to the increase in defect density rather than fine precipitates. 相似文献
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采用中红外CO2激光差频产生太赫兹波是提高转换效率和输出功率的一种有效方法。根据差频过程中的三波互作用对AgGaS2晶体进行了理论分析,数值模拟了oeo类和oee类两种匹配条件下差频产生太赫兹波的角度调谐曲线,并计算了光波在晶体中的走离角和允许参量。另外,还考虑了晶体的有效非线性系数和理论功率转换效率。研究结果表明,AgGaS2晶体适用于中红外CO2激光差频产生可广泛调谐的太赫兹波。 相似文献
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K. J. Bachmann E. Buehler J. L. Shay G. W. Kammlott 《Journal of Electronic Materials》1974,3(2):451-473
Heterojunctions of n-type CdSnP2 on p-type InP substrates are prepared by LPE from Sn-solutions. The significance of the tipping arrangement, of the initial
solution composition and of the temperature program for preparing LPE layers of high quality is discussed. Heterodiodes cleaved
from such LPE wafers electroluminesce under forward bias between 1 μm and 1.8 %m with internal quantum efficiencies approaching
1.8% at room temperature. When used as photovoltaic detectors, the quantum efficiency of these diodes surpasses that of Si
for λ > 1.09 μ, and exceeds 1% for all wave-lengths between 0.96 and 1.3 μ. 相似文献
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Melt texture process of YBCO leads to a YBa2Cu3O7−x matrix where Y2BaCuO5 particles are observed. The Y2BaCuO5 inclusions size and distribution depend upon several parameters: YBa2Cu3O7-x grain size in the presintered, heating rate, dopants. The influence of an excess of Y2BaCuO5 and/or BaSnO3 on these Y2BaCuO5 particles are observed in the liquid phase and in the texture domain. According to the dopant used, two kinds of coarsening
of Y2BaCuO5 can be observed: an isotropic and an anisotropic. The control of the distribution of Y2BaCuO5 particle size is of primary interest to improve the efficiency of the MTG process. In particular large cooling rate (5°C/h)
during the texture formation could be used by adding Y2BaCuO5 + BaSnO3 to YBa2Cu3O7−x composition. 相似文献