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本文研究了高 T_c 的 Bi_(2-x)Pb_xSr_2Ca_2Cu_4O_y 超导纤维(x=0.3,0.5)的性能和亚结构.晶纤用激光加热基座(LHPG)法生长.结果表明,块状烧结样品拉制成晶纤后,超导相增多,致密度增加,织构化明显,因而超导性能明显改善.在拉制样品过程中,虽然 Pb 有所挥发,但大部分仍留在晶纤内. 相似文献
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纯的TlSrCaCuO体系难以制备1223型超导铜氧化物,报道了合成和用粉末X射线衍射、电子衍射鉴定了一大类新型1223相高T_c超导层型铜氧化物(Tl_(1_x)M_s)(Sr_(2_y)Ba_y)Ca_2Cu_3O_x,其中M为Cr或V,包括(Tl_(0.75)Cr_(0.25)(Sr_(2_y)Ba_y)Ca_2Cu_3O_x,(Tl_(0.75)V_(0.25))(Sr_(2_y)Ba_y)Ca_2Cu_3O_x,(Tl_(1_x)Cr_x)Sr_2Ca_2Cu_3O_x和(Tl_(1_x)V_x
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高Tc氧化物超导体的元素替代效应(Ⅰ) 总被引:5,自引:0,他引:5
本文就高Tc氧化物超导体中的元素替代效应,尤其是对123相化合物中不同原子位置上部分元素替代所导致的晶体结构、氧含量、正常态和超导态性质,以及载流子浓度等的变化作了系统的评述。深入讨论了从中给出的有关高温超导电性微观机制的信息。 相似文献
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本文简要地描述了已发现的铜氧化物超导体的不同结构类型,并按其中CuO平面的不同连接和分隔方式做了分块划分。利用这些连接、分隔的不同方式可以组合出新的结构类型。这种思想已被铅系的Pb-2222(PbBaSr(NdCe_2)Cu_3O_y),LaBa(NdCe)_2Cu_3O_y和Ta-1222等新化合物的设计和成功制备所证实。最后提出了寻求新型层状铜氧化物和超导新体系的可能方向。 相似文献
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We have systematically investigated the doping effect on the Bi2Sr2Ca2Cu3Oy superconductive material. After entering into the crystal lattice, Pb and/or Sb atoms cause not only variations of the temperature condition during the sample preparation process, but also variations of structures and superconductivity. By analyzing the experimental results, we have come to the conclusion that the Pb and/or Sb atoms enter into the Bi-O planes, preferably occupy the sites of Bi ions, regulate the crystal structures and the distribution of oxygen ions in Bi-O planes and nearby lattice sites, thus benefiting the formation of the high-Tc phase and improving the superconductivity. 相似文献
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There was giant flux jumps in high Tc Bi1.7Pb0.3Sr2Ca2Cu3Oy bulk superconductor. The relaxation time, τ, decreased with both the increase of magnetic field and the rise of temperature. The maximum τ was about 40 min.. The average-dM/dt increased with both the increase of magnetic field and the rise of temperature. The minimum average-dM/dt was about 4.1×10−2G/min.. The flux jump weakened with time. It was dependent on the decrease of gradient of magnetic flux density dn/dx in the sample. 相似文献
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用固相反应法合成了名义组分为Bi1.92Pb0.32Sr2Ca1.7Mg0.3Cu3.07Ox的块状样品。X射线衍射谱(XRD)、扫描电子显微镜(SEM)和电子探计X射线分析(EDAX)结果以及块状和粉状试样的交流磁化率测量表明,样品中存在110和85K两个超导相;2223相(110K)首先在2212相(85K)晶体的晶界和外部区域生成。本文认为,最初存
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C. Terzioglu 《Physica B: Condensed Matter》2008,403(18):3320-3325
Gold (Au) diffusion in superconducting Bi1.8Pb0.35Sr1.9Ca2.1Cu3Oy was investigated over the temperature range 500-800 °C by the energy dispersive X-ray fluorescence (EDXRF) technique. It is found that the Au diffusion coefficient decreases as the diffusion-annealing temperature decreases. The temperature dependences of Au diffusion coefficient in grains and over grain boundaries are described by the relations D1=6.7×10−5exp(−1.19 eV/kBT) and D2=9.7×10−4exp(−1.09 eV/kBT), respectively. The diffusion doping of Bi-2223 by Au causes a significant increase of the lattice parameter c by about 0.19%. For the Au-diffused samples, dc electrical resistivity and transport critical current density measurements indicated the critical transition temperature increased from 100 to 104 K and the critical current density increased from 40 to 125 A cm−2, in comparison with those of undoped samples. From scanning electron microscope (SEM) and X-ray diffraction (XRD) measurements it is observed that Au doping of the sample also improved the surface morphology and increased the ratio of the high-Tc phase to the low-Tc phase. The possible reasons for the observed improvement in microstructure and superconducting properties of the samples due to Au diffusion are also discussed. 相似文献
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M. I. Petrov D. A. Balaev I. L. Belozerova S. I. Popkov A. A. Dubrovskii K. A. Shaykhutdinov O. N. Mart’yanov 《Technical Physics》2009,54(8):1130-1134
Low-density polycrystalline Bi1.8Pb0.3Sr1.9Ca2Cu3O
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high-temperature superconductors with a foamlike microstructure and composites consisting of this superconductor and silver
in an amount of 20, 25, and 30 vol % are synthesized. The microstructure, as well as the temperature and field dependences
of the magnetization, M(T) and M(H), are studied. It is found that, in Bi1.8Pb0.3Sr1.9Ca2Cu3O
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high-temperature superconductors and Bi1.8Pb0.3Sr1.9Ca2Cu3O
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+ Ag composites, the diamagnetic response is enhanced and the screening properties are improved compared with high-temperature
polycrystalline superconductors with the same composition that are prepared by the standard technology. The observed effect
is explained by the features of magnetic flux penetration into a porous medium. 相似文献
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Thomas W. Krause R. K. Nkum W. R. Datars 《Physica C: Superconductivity and its Applications》1993,210(3-4):333-342
Measurements of the resistivity and current dependent resistivity for small current densities ranging from 0.03 A/cm2 to 3.0 A/cm2 were performed with two Sn-doped and two Sb-doped polycrystalline Bi1.7Pb0.3Sr2Ca2Cu3Oy samples in magnetic fields up to 1.7 T. Features in the temperature derivative of the resistivity curves were associated with the presence of a superconducting transition between superconducting grains, coupled by weak links with a distribution of critical currents and critical temperatures, and the superconducting transition within grains. The transition between grains was more strongly suppressed in temperature with the application of a magnetic field in samples with weaker coupling between grains. The presence of a transition in a magnetic field due to weak links between grains was verified at 77 K by the observation of a current dependent resistivity in a magnetic field. 相似文献
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采用固相反应法合成了名义组份为Bi2-xPbxSr2Ca2Cu3Oy (x=0.30;0.35;0.40;0.45)的样品。对样品进行了物相和结构分析,同时测量了电阻-温度关系和直流磁化率。结果表明:x=0.35的样品为单相材料,X射线相分析和电子衍射表明其相结构类似2223相,为四方结构,其晶格常数为a=b=5.414?,c=37.106?,且沿a,b两个方向都观察到调制结构。电阻和直流磁化率测量结果显示:在温度高于50K以上,仅存在一个107K超导相。此外,单相材料的制备条件(组分、烧结温度、室温下淬火及淬火速率)非常苛刻。如同1-2-3相材料一样,氧含量不仅影响样品的成相规律、零电阻温度,而且还严重影响其正常态的输运性质。
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