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J. Pastrňák 《Czechoslovak Journal of Physics》1961,11(6):452-453
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本文在作者的 YBa_2Cu_3O_6+(1/2)O_2(?)YBa_2Cu_3O_7可逆转变模型的基础上,提出了氧在如上反应过程中的活度概念,并讨论了可逆转变反应的标准自由焓和活度系数. 相似文献
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ABSTRACTThe blue phase of YBa2Cu3O7- δ (YBCO) family, Y2Cu2O5 (Y202) nanoparticles were prepared and doped into (YBCO) superconductor and the effect of doping on critical current density and critical temperature was investigated. Y202 nanoparticles with particle sizes of 47, 107 and 206?nm were prepared by a sol–gel combustion method and added into the YBCO superconductor by 0.5–2?wt.%. XRD and scanning electron microscope measurements were used to characterize the samples. The measurement of critical current density at 77?K revealed that the doped superconductors had larger critical current density compared to the undoped superconductors. For a fixed dopant concentration, by increasing the size of nanoparticles, the Jc was increased. For the samples including 0.5?wt.% of nanoadditives, Jc was higher. The highest critical current density of 137?A/cm2 was measured for the superconductors containing 0.5?wt.% of 206?nm Y202 nanoparticles. Also, by increasing the nanoparticles concentration, the Tc was reduced. 相似文献
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我们采用电子束曝光和氩离子刻蚀技术制备了YBC纳米桥,在此基础上得到高温rfSQUID,器件的磁通噪声为4×10^-4Φ/√Hz,磁场分辨率为2.0pT/√Hz,对没有三角波的器件,经过EDTA后腐蚀技术对纳米进行弱化处理,部分器件出现了三角波。 相似文献
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根据YBa_2Cu_3O_(7-δ)超导定向膜经不同温度退火后的红外反射光谱和不同掺Zn量的YBa_2Cu_(3-z)Zn_xO_(7-δ)的红外吸收光谱在500-700厘米~(-1)特征峰的变化,进一步讨论了YBa_2Cu_3O_(7-δ)中Ba-Ba层间和Y-Ba层间Cu-O键伸缩振动的三个红外吸收峰强度变化的本质。用红外入射光穿透深度随Y系样品电阻率提高而增大和对应二维CuO_2网络中Cu-O反称振动吸收的590厘米~(-1)峰强度变化不受氧缺位影响的事实,说明590厘米~(-1)的吸收峰不是氧缺位诱导的准局域振动模。同时对620厘米~(-1)和550厘米~(-1)吸收峰的解释也给予了必要的补充和验证。 相似文献
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测量了c轴高度定向的YBa2Cu3O7-δ高Tc超导薄膜经300~750℃退火后的红外反射光谱和不同掺Zn量的YBa2Cu3-xZnxO7-δ块状材料的红外吸收光谱。根据这些光谱中Cu-O吸收峰的变化,证实了在YBa2Cu3O7-δ体系的红外光谱中,630cm^-1、590cm^-1、和550cm^-1三个吸收峰分别对应的Cu-O伸缩振动膜,以及与氧缺位的关系。并讨论了二维电子气屏蔽对吸收峰的影响 相似文献
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J. Zieglowski S. Blumenröder A. Freimuth H. Schmidt E. Zirngiebl D. Wohlleben H. J. Schmidt 《Zeitschrift für Physik B Condensed Matter》1988,71(4):429-436
The magnetostriction (MS) of REBa2Cu3O7– (RE=Y, Nd, Eu, Gd, Ho, Er, Yb) is reported as a function of magnetic field and temperature forH<5 T and 1.5H>1 T. The MS is much larger when the rare earth carries a magnetic moment, as usual, but the volume MS observed with moment carrying REBa2Cu3O7– is larger than that of nonsuperconducting intermetalics. This effect is explained by the shielding currents which are induced by the 4f magnetic moments in the superconducting CuO-lattice. The thermal expansion of GdBa2Cu3O7– shows a large peak at the ordering temperature of 2.2 K in both the superconducting and the nonsuperconducting samples. 相似文献
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采用脉冲激光方法,先在YSZ(yttria stablized zirconia)衬底上制备(YBa2Cu3O7-y)/YSZ高温超导薄膜,再用较低的激光能流密度(1.2-1.0Jcm^-2)沉积一层NBCO(NdB2Cu3O7-x)薄膜,形成NBCO/YBCO/YSZ双层超导薄膜。在制备完当时,存放40天和存放400天后分别对薄膜进行了X射线衍射分析和电阻-温度曲线测量。结果表明,NBCO/YBCO/YSZ双层膜的转变温度、结晶度和表面稳定性及光滑度都优于YBCO/YSZ薄膜的。在YBCO/YSZ上使用较低的激光能量可以制备出优质的c轴取向NBCO高温超导薄膜。 相似文献
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Cu2O半导体超微粒子的光学性质 总被引:3,自引:0,他引:3
本文研究了表面修饰的Cu2O半导体超微粒子的光学性质.在Cu2O超微粒子中未观察到显著的量子尺寸效应,但测量到很强的宽带光致发光,且随着激发波长变短,其发光带的峰位蓝移,发光带宽度增加.最后,分析了Cu2O超微粒子的宽带发光机制,并讨论了热处理对超微粒子的发光强度的影响. 相似文献
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本提出PrBa2Cu3O7中的Pr-O键长的缩短是由于Pr-O键含有明显的共价成份,中阐述了这种共价性作用的性质和原因。讨论了这种化学键对PrBa2Cu3O7电子结构的影响,这性解释了PrBa2Cu3O6+x中复杂的反铁磁有序。 相似文献
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本给出了具有高密度孪晶界c取向YBa2Cu3O7-x外延薄膜存在涡旋玻璃转变及很好的标度行为的实验证据,在有a方向昌粒或45°晶界的GdBa2Cu3O7-x外延薄膜中存在涡旋玻璃转变但在转变温度附近观察到磁通蠕动和热激活磁通流的某些特征。 相似文献
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采用水热法和热处理技术制备了不同掺杂比例的Zn_(1-x)Cu_xAl_2O_4(x=0,0.05,0.10,0.15,0.20)纳米颗粒,通过X射线衍射(XRD)、场发射透射电子显微镜(FETEM)、傅里叶红外光谱(FT-IR)、X射线光电子能谱(XPS)、光致发光光谱(PL)和紫外可见光谱(UV-Vis)对样品的晶体结构、形貌、元素分布、结合能和光学性能进行表征,并通过第一性原理计算得到了ZnAl_2O_4结构中存在的各种缺陷的能带结构。实验结果表明本方法制备的Zn_(1-x)Cu_xAl_2O_4纳米颗粒为尖晶石结构,XPS能谱说明Zn_(0.9)Cu_(0.10)Al_2O_4样品中Cu~(2+)全部占据了四面体位置,PL光谱显示Cu~(2+)掺杂的样品出现了猝灭现象,紫外光谱表明Cu~(2+)掺杂后样品出现了新的吸收峰。并结合第一性原理计算对样品的光学性质给出了合理解释。 相似文献
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A. Crisan V.S. Dang P. Mikheenko Y.Y. Tse A. Sarkar J. Bowen J.S. Abell 《Physica C: Superconductivity and its Applications》2010,470(1):55-60
Using Pulsed Laser Deposition we have fabricated thick quasi-multilayers composed of incomplete layers of PrBa2Cu3Ox (PrBCO) nano-dots and layers of YBa2Cu3O7?δ (YBCO). The number of such sequences was between 2 and 6, with the thickness of individual YBCO layers between 565 and 885 nm, and total thickness between 1.13 and 5.31 μm. For the thinner quasi-multilayer, DC magnetization studies showed an increase in the critical current density Jc at all fields in comparison with a pure YBCO reference sample, while the thicker samples showed an increased Jc only in high fields. We have also investigated the frequency dependence of Jc from AC susceptibility studies and found that the pinning potential is well described by a logarithmic dependence on current density. Pinning potentials in PrBCO/YBCO quasi-multilayers also proved to be higher than in the reference sample at high fields. From angle-dependent transport measurements we have found indications of strong pinning centres induced by the (PrBCO) nano-dots, both isotropic and c-axis correlated. 相似文献
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本文译自Asia—Pacific Physics News(Vol.2,1987年11月),原编者指出制作高温超导体是很容易的,美国、日本和英国的中学生已经制作出了他们自己的样品。并认为这也是发展中国家的中学,在力所能及的范围内,接触物理学尖端领域的少数几个实验之一。文中介绍的配方是1987年6月19日由美国物理教师联合会(AAPT)的会议制订的。 相似文献