共查询到20条相似文献,搜索用时 23 毫秒
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用固态反应法制备了YBa2Cu3-xFexOy(x=0—0.5)一系列样品,反应在空气中进行.运用正电子湮没技术、扫描电子显微镜和X射线衍射进行了研究,并测定了氧含量.正电子湮没结果发现,x=0.12时短寿命分量τ1和长寿命分量τ2都存在一异常变化.X射线衍射和扫描电子显微镜研究分别表明,材料在x=0.12—0.15区间内发生正交四方相变,晶粒尺寸突然由小变大.通过对上述实验结果的分析可以得到,在该类材料中,正电子对结构相变十分敏感;另外,当Fe掺杂量增大到一定程度时,Fe原子由随机分布变为成簇分布
关键词:
Fe掺杂YBCO
高温超导电性
正电子湮没
结构相变 相似文献
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Abstract Single crystals of Indium Selenide are prepared by vapour growth technique as it is difficult to prepare large single crystals by vertical Bridgman technique. The effect of stochiometric changes and doping have been studied. The electrical properties of n-type single crystals are discussed. 相似文献
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J. L. Tallon R. G. Buckley M. R. Presland P. W. Gilberd I. W. M. Brown M. Bowden 《Phase Transitions》2013,86(4):171-190
The preparation, structure and properties of five members of the homologous series Bi2+x(Ca,Sr) n+1 Cu n O2n+4+δ are discussed, namely for n = 0, 1, 2, 3 and ∞. The two end members are insulating phases with a fixed oxygen stoichiometry but the members n = 1, 2 and 3 are superconducting phases with Tc depending on the calcium to strontium ratio and on oxygen stoichiometry as determined by annealing temperature and oxygen partial pressure. Maximum zero resistance Tc 's obtained are n = 1: 76 K, n = 2: 91 K and n = 3: 106 K. The effects of Pb-substitution in n = 2 and n = 3 are discussed with particular reference to the stabilisation of the latter phase. Rare-earth substitution is shown to raise Tc for n = 2 to at least 101 K without the introduction of the n = 3 phase. 相似文献
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V. F. Nesterenko 《高压研究》2013,33(5-6):767-772
Abstract The properties of high Tc-ceramics (Y-123, Bi-1112, Bi-4334, Bi-4457, (Bi-Pb)-4457) under shock loading and subsequent heat treatment were investigated. The peculiarities of their structure, tecture creation, changes of superconductivity parameters depending on loading conditions at P~ 10GPa Were revealed, and regimes of heat treatment were determined. The possibilities of obtaining crack-free cylindrical superconducting shields as well as strong metal high-Tcceramic joints were demonstrated. 相似文献
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G Padmaja A V Ravi Kumar V Vidyalal P Radhakrishnan V P N Nampoori C P G Vallabhan 《Pramana》1989,32(5):L693-L698
Laser induced plasma emission spectra from highT
c superconducting samples of YBa2Cu3O7 and GdBa2Cu3O7 obtained with 1.06μm radiation from a Q switched Nd:YAG laser beam has been analysed. The results clearly show the presence of diatomic oxides
in addition to ionized species of the constituent metals in the plasma thus produced. 相似文献
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用Mg/B多层膜退火的方法制备了一系列MgB2超导薄膜,研究了退火温度、退火时间和薄膜厚度对于MgB2薄膜性质的影响.厚度为250 nm的Mg/B多层膜经400 ℃低温退火后已经生成超导相,此厚度薄膜750 ℃下退火20—30 min实现最佳超导转变温度(Tc).前驱膜分层厚度相同时,随着薄膜厚度减小MgB2薄膜Tc明显降低,而且较薄的膜Tc
关键词:
2超导薄膜')" href="#">MgB2超导薄膜
电子束蒸发
超导成相 相似文献
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Tadashi Kobayashi Hiratoshi Katsuda Yukio Sakabe Kiyoshi Iwai Seiji Kanba 《Phase Transitions》2013,86(3):215-223
EPR spectra of superconducting YBa2Cu3O7-δ and insulating Y2BaCuO5 have been examined. The intensity of Cu2+ ions in YBa2Cu3O7-δ is about 1/3000 of that in Y2BaCuO5 at room temperature. Owing to the Meissner effect in the superconducting state, the EPR signal of Cu2+ ions in YBa2Cu3O7-δ disappears; moreover the EPR signal of DPPH deposited on the YBa2Cu3O7-δ specimen is shifted. An additional EPR line is found for YBa2(Cu2.94Cr0.06)O7-δ at temperatures below 113K; this can be related to the phenomenon of superconductivity. 相似文献
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A. Laurinavicius F. Anisimovas A. Deksnys V. Lisauskas B. Vengalis 《International Journal of Infrared and Millimeter Waves》1993,14(10):2261-2266
For the first time millimeter waves are used for non-destructive diagnostics of superconducting layers and their quality control. The quality of the whole layer depending on TC and TC is determined by local transmission of millimeter waves. 相似文献
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Muller and coworkers have introduced the concept of a superconducting glass to explain some magnetization data in highT
csuperconductors. We explain this data using conventional ideas of type-II superconductivity. 相似文献
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Abstract By means of a four-point resistivity method the critical temperature (Tc) of the tetragonal high temperature super-conductor CaLaBaCu3Ox was studied for pressures up to 9 GPa. The pressure dependence of Tc is small and negative, dTc/dp = - 0.77 K/GPa, and agrees with the general trend observed in previous data. 相似文献
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Studies on the superconductivity behaviour of pure and doped (Pb,TI) Bi4Sr3Ca3Cu4O16 phases are reported. Effect of oxide additives PbO, BaPbO3 and BaBiO3 has also been examined. Results show that an oxygen treatment at 600°C for 12 h during the final stages of the synthesis has the beneficial effect of sharpening the Tc zero of the 4334 Bi-composition. Pb and TI substitution has only a marginally beneficial effect on the Tc , though it is not definitely known whether substitution is actually occurring in the system. PbO as an additive raises the Tc zero to 89 K, whereas other additives do not basically affect the properties of the 4334 system. 相似文献
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D. P. Belanger 《Phase Transitions》2013,86(1-4):53-89
Experiments in d = 2 and d = 3 random-field Ising systems are reviewed. Random fields destroy the phase transition for the d = 2 system Rb2Co x Mg1-xF4. The d = 3 Fe x Zn1-xF4 system shows a new phase transition with unusual dynamics. Extreme critical slowing down plays an essential role in the d = 3 measurements. Experiments on the related d = 3 systems Mn x Zn1-xF2 and Fe x Mg1-xC12 are also discussed. 相似文献
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The present paper attempts to study the Neel temperature of bilayer antiferromagnetic cuprate YBa2Cu3O6.2 within anisotropic Heisenberg model. The double time Green’s function formalism within random phase approximation (RPA) has
been used to obtain various correlation functions. The magnetization and the Neel temperature (T
N) are evaluated. It is observed that the ratio of intrabilayer to inplane exchange coupling (r=J⊥/J‖) plays an important role in the magnetic dynamics of bilayer systems. The recent experimental data of bilayer system YBa2Cu3O6.2 have been used to estimate the ratio r from the expression for Neel temperature. The estimated values of spin gap and the ratio of hopping matrix elements t⊥/t‖ are found to be in fairly good agreement with the existing experimental results. 相似文献
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Abstract An update is given of all published data on δTc/δp, extending our previous review. Implications of new data for the RVB model are discussed. Under particular assumptions a striking discrepancy is found. 相似文献
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S K Gupta V R Katti D P Gandhi S C Gadkari S C Sabharwal K K Gupta A K Rajarajan L C Gupta R Vijayaraghavan 《Pramana》1988,30(4):L341-L344
The results of our initial efforts to deposit thin films of YBa2Cu3O7−x
system on sapphire substrate are described. The deposited films are shiny black in appearance and are of quite uniform chemical
composition. The annealed films exhibit zero resistance superconducting transition temperatureT
c(R=0) ranging between 23 K and 30 K. 相似文献