高Tc超导材料R—T曲线的交流动态测量

本文描述了用锁相放大器及交流双回路四端法来测量Y·Ba·Cu·O型高T_c超导材料的电阻—温度(R—T)曲线的细节,获得了满意的结果。     

超导体相变的热力学描述

本文从教学的角度,对超导体的相变问题用热力学理论作一些讨论。     

钇钡铜氧系统单相高T_c超导体的研究

采用固相反应法制样,使用两组初始原料BaO—CUO—Y_2O_3和BaO—Cu_2O—Y_2O_3合成出超导中点转变温度93.6K,零电阻温度92·OK,转变宽度△T_c=1.2K,起始抗磁转变温度92.9K单相陶瓷超导体.讨论了不同烧结条件与物相形成关系等问题.     

Space qualification mechanical tests of HTS filters for satellite application

High performance high-temperature superconducting （HTS） filters have been designed and constructed for satellite application. The filters are actually a superconducting integration of an 8-pole band-pass filter with an adjustable band-stop filter onto a single piece of LaAIO3 substrate （with dimension of 0.5x45x20 mm3）. Typical results of the filters, i.e., Filters A （made by YBCO） ＆ B （made by TBCCO） will be reported. The measured responses of Filter A showed excellent specifications, e.g., an insertion loss less than 0.1 dB, a return loss better than -22.5 dB in pass-band, band-edge steepness greater than 12 dB/MHz and out-of-band rejection at a certain band deeper than -110 dB. To satisfy the requirement of rocket launch and space operation, three filters of the above design have undergone mechanical environmental simulation tests for space qualification. Detailed analysis of the response curves of Filter B measured before and after the tests showed that no noticeable change in the performance can be found. All the filters passed the rigorous ground simulation tests, which is the first time in China for HTS devices and provided a solid foundation for satellite applications of high-temperature superconductors in the near future.     

从一个佯谬到一个超导新效应的发现

存在两条超导线，线2的半径是线1的两倍。同种材料，因而它们具有相同的临界电流密度JC和临界磁场BC。现在将两条超导线都通以密度为Jc的超导电流，设它们在两条导线表面产生的磁场为Bc1和Bc2，因为是相同的材料，应该有Bc1=Bc2，但是根据载流导线产生的磁场的计算，我们可以立刻得到Bc1／Bc2=2，这就产生了佯谬(翟氏佯谬)。这个佯谬也可以从另一个角度表述为：对任何一种超导导线，存在一个临界半径，当线的半径超过这个值时，即使超导线的半径再增加，它所能承载的最大超导电流也不能再增大了。显然，这与人们的日常经验与概念相矛盾，也与西尔斯比定则不相符合。对上面佯谬的解答中导致了一个新的超导效应的发现。我们将从精简的理论给出解释，并引用实验结果。     

Structure properties for the superconductor MgCNi3 under high pressure with synchrotron radiation

The recent discovery of superconductivity at 39 K in the superconductor MgB2[1] shows that intermetallic compounds with simple structure types are worth serious reconsideration as sources of new superconducting mate-rials. Subsequent to this discovery, He et al. observed a new intermetallic superconductor MgCNi3[2] at about 8 K. The perovskite crystal structure for MgCNi3 is shown in Fig. 1, with the atomic positions: Mg: 1a (0,0,0), C: 1b (0.5,0.5,0.5) and Ni: 3c (0,0.5,0.5). This mater…     

超导涡旋系统的非平衡态相变

利用三维各向异性XY模型和电阻分流结动力学,研究了较强钉扎势下第二类层状超导体涡旋系统的非平衡态相变.结果发现,平衡态的涡旋玻璃相可在电流驱动下转变为运动玻璃相.在低温下系统经历了三次相变:随电流的增加,系统首先从运动涡旋玻璃相转变为运动Bragg玻璃相,再转变为运动Smectic相,最后融化为运动液体相.     

磁性和非磁性杂质对高Tc超导材料结构相变的影响

本文研究了磁性和非磁性杂质对高Tc超导体结构相变温度的影响,结果和已有的实验定性符合。     

YBa2Cu3O7—x超导体的季铵盐制备法

以尚未报道过的碳酸季铵盐为沉淀剂制备YBa_2Cu_3O-(7-x)超导体,既保持了原有碳酸盐法沉淀齐全的优点,又去除了碳酸盐法常带入碱金属离子的缺点,一次灼烧,Tc即为91.6K,经电磁学性质测定和物相分析,得出样品有较好的单相均匀性。