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1.
临界电流密度(Jc)是超导薄膜、块材、带材等材料的基本性能参数,决定了超导器件及设备的性能和稳定性,简易、准确的无损Jc测量方法对超导材料特性研究及超导器件的性能保障具有重要意义。本文介绍一种基于三次谐波测量的高温超导薄膜局部临界电流密度测量方法和测量装置。研究显示,在一定幅值的初级线圈交流磁场激励下,Ⅱ型超导体会产生非线性响应,通过分析次级线圈中三次谐波分量的幅值变化,可以推算超导体的局部临界电流密度。我们搭建了一套基于此原理、适用于液氮条件的测量装置。通过对比实验,对测量的准确性进行了验证,尤其针对微弱的微纳伏量级被测信号,采取了必要的噪声抑制措施,并通过对测量数据的校正,提高了测量的准确度。实验研究显示,基于三次谐波测量的方法对于超导薄膜的临界电流密度的测量准确度较高,进行误差修正后,测量装置的误差小于10%。超导薄膜感应法测量装置的搭建十分方便,而且应用灵活,对于大面积超导薄膜的临界电流密度分布测量具有十分显著的优势。  相似文献   

2.
临界电流密度Jc是评价超导薄膜质量的重要参数之一.采用Jc测量装置可以准确、快速、无损检测Φ2~3英寸双面膜的Jc均匀性.该装置是利用高温超导薄膜的超导转变对线圈内感应电压产生的变化这一原理,测量线圈由初级和次级组成.所用信号频率为20kHz.次级信号在同样频率下由锁相放大器检测.测量过程全部由计算机控制.对于超导微波滤波器应用所要求的高质量Φ2~3英寸双面超导薄膜材料,必须具有高的Jc和低的Rs值.采用该装置测量超导薄膜的Jc均匀性,与Rs对应关系进行分析,将有助于超导薄膜的质量控制.  相似文献   

3.
临界电流密度Jc是评价超导薄膜质量的重要参数之一,采用Jc测量装置可以准确、快速、无损检测Ф2~3英寸双面膜的Jc均匀性。该装置是利用高温超导薄膜的超导转变对线圈内感应电压产生的变化这一原理,测量线圈由初级和次级组成,所用信号频率为20kHz,次级信号在同样频率下由锁相放大器检测,测量过程全部由计算机控制,对于超导微波滤波器应用所要求的高质量Ф2~3英寸双面超导薄膜材料,必须具有高的Jc和低的Rs值,采用该装置测量超导薄膜的Jc均匀性,与Rs对应关系进行分析,将有助于超导薄膜的质量控制。  相似文献   

4.
通过使用扩展后的Mikheenko等人提出的临界态模型,我们用数值计算方法找出了圆盘状超导薄膜在垂直外磁场中的磁通密度分布和电流密度分布.其中考虑到临界电流密度Jc会随外磁场Ha改变而变化,所以我们采用了Kim型表达式Jc(H)=J0/(1+(|H|/H0)n).计算出的初始磁化曲线和磁滞回线与YBCO薄膜的实验曲线(T=51~77K)符合得很好,说明这个方法在这段温区内比较成功.另外我们也得出并讨论了特征参数J0,H0随温度的变化关系.  相似文献   

5.
采用TSSG法在1 atm氧气氛下生长出Y1-xPrxBa2Cu3O7(x=0.07215)超导单晶样品;测量了该单晶样品在不同温度下的磁特性;根据Bean临界态模型,计算出不同温度下的临界电流密度Jc对磁场H的依赖关系;在对该样品的直流磁化研究中观测到了峰效应。随着温度的降低,样品的临界电流密度明显增加。  相似文献   

6.
高温超导电力装置一般工作于低磁场情况下,测量超导带材在低场下的临界电流特性非常重要.文中通过自行设计的实验平台,采用四引线法对Y系超导带材低场下的临界电流特性进行了测量,得到了带材临界电流随外加磁场变化的曲线,并与Bi系带材低场下的临界电流特性进行比较.  相似文献   

7.
基于Kim临界态模型,通过考虑超导块材内部屏蔽电流的穿透历史过程,讨论了场冷条件下临界电流密度对高温超导悬浮系统磁悬浮排斥力和吸引力的影响.结果显示:最大超导磁悬浮排斥力和吸引力均随临界电流密度的增加呈指数关系增加,并趋于饱和;场冷条件下的磁悬浮力回滞能量损耗远高于零场冷情况;存在一个磁悬浮力比率κ,κ值对于评价大电流...  相似文献   

8.
针对兆伏安级容量的超导变压器,通过绕组初步设计,考虑导体的电流密度、载流量和交流损耗,提出面向大容量超导变压器应用的新型超导复合导体结构,介绍了含内外超导层的新型高温超导复合导体的结构。引入电流矢量T和磁矢量势A的方法,考虑临界电流密度J_c和磁场B的关系,建立了导体不对称三维数值载流模型,计算分析了不同结构参数对导体临界电流的影响规律。通过绕制的新型高温超导复合导体短样,在液氮环境下对其自场临界电流进行了测量,计算结果和实验结果基本吻合,验证了模型的合理性。  相似文献   

9.
临界电流密度(J_c)是超导材料的重要特征参数之一,精确的测量临界电流密度对研究超导材料特性及超导器件稳定性具有重要意义.本文介绍了一种基于经典电磁感应理论和超导技术理论测量YBCO超导薄膜临界电流密度的方法和测试装置.研究显示,在液氮环境下,将超导薄膜加入初级线圈和次级线圈中间会明显影响次级线圈的接收效果.我们根据此测量方法搭建了一种测量YBCO薄膜临界电流密度的实验装置.在分析实验测量误差后,通过实验的对比,得到了加入超导薄膜对次级线圈的感应电压的影响,并分析感应电压与线圈互感之间的关系,从而算出超导薄膜的临界电流密度.实验通过噪声抑制和数据校正,准确地测量了超导薄膜的临界电流密度.  相似文献   

10.
沈腾明  李果  赵勇 《低温物理学报》2005,27(Z1):864-869
为了研究超导材料中高温超导相颗粒的钉扎行为,在Ar气保护条件下,采用固相反应法制备了质量百分比为0,3,5和10%Bi2Sr2CaCu2O8含量的MgB2块状样品.用X射线衍射和扫描电子显微镜对样品进行了显微结构分析;用物理性能综合测试系统振动样品磁强计(最大磁场9T)测量了所有样品在不同磁场下的直流M(T)曲线,并测量了不同温度下的准静态磁化曲线,通过Bean临界态模型分析出Jc(H)曲线.随着掺杂量的增大掺杂后Tc基本不变,转变宽度略为增大;相比于未掺杂样品,掺杂量为3 wt%样品抗磁信号和临界电流密度有较大提高.显微结构分析结果表明,部分Bi2Sr2CaCu2O8分解为Cu2O和其它杂相,有部分Bi2Sr2CaCu2O8颗粒保留在样品内部,成为有效的钉扎中心.最后本文对超导体中的高温超导相颗粒的钉扎行为进行了分析.  相似文献   

11.
张旭  吴之珍  周铁戈  何明  赵新杰  阎少林  方兰 《中国物理 B》2011,20(2):27401-027401
The critical current density J c is one of the most important parameters of high temperature superconducting films in superconducting applications,such as superconducting filter and superconducting Josephson devices.This paper presents a new model to describe inhomogeneous current distribution throughout the thickness of superconducting films applying magnetic field by solving the differential equation derived from Maxwell equation and the second London equation.Using this model,it accurately calculates the inductive third-harmonic voltage when the film applying magnetic field with the inductive measurement for J c.The theoretic curve is consistent with the experimental results about measuring superconducting film,especially when the third-harmonic voltage just exceeds zero.The J c value of superconducting films determined by the inductive method is also compared with results measured by four-probe transport method.The agreements between inductive method and transport method are very good.  相似文献   

12.
YBCO高温超导磁体临界电流密度快速确定方法   总被引:6,自引:0,他引:6  
基于绘图法基本原理,以及YBCO高温超导带材的临界电流特性,采用有限元电磁场分析软件AnsoftMaxwell建立了空心圆柱磁体模型.根据磁场分布、并考虑到带材的临界电流密度随磁场大小和方向的变化关系,给出了影响磁体工作电流特性的磁场的分布.基于以上工作提出了一种利用Ansoft电磁场分析软件快速确定YB-CO高温超导带材临界电流密度的方法.  相似文献   

13.
给出了第二类超导体临界电流密度随样品尺寸及外加磁场变化的一个临界态模型计算。计算中考虑了样品中混合态与迈斯纳态共存的情况。用该模型对Tl2Ba2Ca2Cu3O10样品的实验测量结果进行了模拟计算,并讨论了有关问题。  相似文献   

14.
文中以LaAlO3为衬底,制作了一层Tl-2212高温超导薄膜,并在薄膜上生长一层较薄的CeO2缓冲层,然后再在上面生长一层Tl-2212高温超导薄膜。经过测量,研究了多层膜结构对超导薄膜临界电流密度的影响。结果显示,在缓冲层的结晶过程中超导薄膜的晶格受到影响,结晶过程中的处理很容易诱导上面一层Tl-2212超导薄膜产生杂相,导致临界电流密度降低。  相似文献   

15.
王三胜  李方  吴晗  张竺立  蒋雯  赵鹏 《物理学报》2018,67(3):36103-036103
低能氩离子束轰击并后退火处理的离子束表面改性,会影响高温超导薄膜的表面结构和超导特性,但是其中的深刻微观机理不清楚.本文通过连续改变离子束轰击时间,系统研究了离子束表面改性对于超导膜结构和临界电流密度的影响.通过扫描电子显微镜、X射线衍射、J_(c-scanning)测试表征样品的结构特性和超导特性,并得出内应变、氧空位缺陷等参量.研究表明,经过表面改性的钇钡铜氧(YBa_2Cu_3O_(7-δ),YBCO)薄膜,随轰击时间增加表面形貌会变得更加均匀致密,a轴晶粒消失,并且临界电流密度有了显著的提高.由化学键收缩配对模型分析得出,临界电流密度的提高与薄膜内应变增大和引发的局部YBCO结构中Cu—O键收缩有关.  相似文献   

16.
For obtaining pure phase T12Ba2Ca2Cu3O10 (T1-2223) films with good superconducting properties, the growth technique is improved by dc magnetron sputtering and a triple post-annealing process. The triple post-annealing process comprises annealing twice in argon and once in oxygen at different temperatures. In the first low-temperature annealing phase in argon, T12Ba2CaCu2O8 (T1-2212) is obtained to effectively minimize evaporation in the next step. With the increase of temperature in the second annealing stage in argon, the previously prepared T1-2212 inter-phase is converted into T1-2223 phase. An additional annealing in oxygen is also adopted to improve the properties of T1-2223 films, each containing an optimal oxygen content value. The results of X-ray diffraction (XRD) θ-2θ scans, 09 scans and rotational φ scans show that each of the T1-2223 films has a high phase purity and an epitaxial structure. Smooth films are observed by scanning electron microscopy (SEM). The critical temperatures Tc of the films are measured to be about 120 K and the critical current densities Jc can reach 4.0 MA/cm2 at 77 K at self field.  相似文献   

17.
The engineering current density in YBCO coated conductor applications can be improved in two ways. Either the critical current density should be improved or the superconducting films made thicker. Unfortunately, it has often been observed that the average critical current density decreases when the thickness of films increases. Suggested reasons for this behaviour include e.g. two dimensional pinning properties, microcracks and imperfect crystallographic alignment. However, it is often forgotten that the self-field effect unavoidably reduces the critical current density when the thickness of YBCO films increases and thereby total current rises. In this paper, the influence of self-field on the average critical current density is studied computationally as a function of film thickness. The situation is also scrutinized at different external magnetic fields in order to find ways to distinguish self-field effects from problems related to the manufacturing process. For this purpose, critical current measurements in external field perpendicular to the film surface are proposed.  相似文献   

18.
Key questions for any superconductor include: what is its maximum dissipation‐free electrical current (its ‘critical current') and can this be used to extract fundamental thermodynamic parameters? Present models focus on depinning of magnetic vortices and implicate materials engineering to maximise pinning performance. But recently we showed that the self‐field critical current for thin films is a universal property, independent of microstructure, controlled only by the penetration depth. Here, using an extended BCS‐like model, we calculate the penetration depth from the temperature dependence of the superconducting energy gap thus allowing us to fit self‐field critical current data. In this way we extract from the T ‐dependent gap a set of key thermodynamic parameters, the ground‐state penetration depth, energy gap and jump in electronic specific heat. Our fits to 79 available data sets, from zinc nanowires to compressed sulphur hydride with critical temperatures of 0.65 to 203 K, respectively, are excellent and the extracted parameters agree well with reported bulk values. Samples include thin films, wires or nanowires of single‐ or multi‐band s ‐wave and d ‐wave superconductors of either type I or type II. For multiband or multiphase samples we accurately recover individual band contributions and phase fractions.  相似文献   

19.
The structure of buffer layers and deposited YBa2Cu3O x (Y123) films with a high critical current density (~106 A/cm2) has been investigated by different methods. These superconducting films and buffer layers are found to have a fine-grained structure, which, along with the high texture of Y123 films of the (001) type, is believed to be responsible for the high critical current density. An unusual texture is revealed in buffer layers, which differs from that of substrates and Y123 films. The superconducting films deposited on buffer CeO2 layers exhibit a system of orthogonal lines; in the case under consideration, this is a manifestation of a domain structure with Y123 particles at boundaries.  相似文献   

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