快重离子辐照对YBa2Cu3O7–δ薄膜微观结构及载流特性的影响  

Effect of swift heavy ions irradiation on the microstructure and current-carrying capability in YBa2Cu3O7–δhigh temperature superconductor films

作　　者：刘丽 刘杰[1,2] 曾健 翟鹏飞[1,2] 张胜霞 徐丽君[1,2] 胡培培 李宗臻[1,2] 艾文思 Liu Li;Liu Jie;Zeng Jian;Zhai Peng-Fei;Zhang Sheng-Xia;Xu Li-Jun;Hu Pei-Pei;Li Zong-Zhen;Ai Wen-Si(Institute of Modern Physics,Chinese Academy of Sciences,Lanzhou 730000,China;School of Nuclear Science and Technology,University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院近代物理研究所,兰州730000 [2]中国科学院大学核科学与技术学院,北京100049

出　　处：《物理学报》2020年第7期274-281,共8页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11675233,11690041,11705246);中国科学院“西部之光”青年人才项目和甘肃省自然科学基金(批准号:18JR3RA392)资助的课题.

摘　　要：钇钡铜氧(YBCO)高温超导材料在能源、交通等方面具有广泛的应用前景,然而强磁场下出现的低临界电流密度问题严重限制了其应用.利用快重离子辐照技术可在YBCO中形成潜径迹对磁通涡旋进行钉扎,从而有效改善其在磁场下的超导性能.本文利用能量为1.9 GeV的Ta离子对YBCO高温超导薄膜进行辐照,系统地研究了不同离子注量下YBCO薄膜的微观结构及磁场下电流传输特性的变化情况.研究表明,Ta离子辐照在薄膜中沿入射路径方向产生贯穿整个超导层的一维非晶潜径迹,其直径在5 nm到15 nm之间.结合Higuchi模型分析了快重离子辐照对薄膜中磁通钉扎机制的影响.研究发现:在原始样品中本征面缺陷钉扎是主要的钉扎机制;随着辐照注量的增加,薄膜中的钉扎类型逐渐转变为由快重离子辐照引入的正常相缺陷钉扎.临界电流密度与磁场的关系可用函数Jc∝B?α 进行拟合.指数α随着注量的增加而降低,当注量为5.0 × 1011 ions/cm2时已由最初的0.784降低至0.375,说明临界电流密度对磁场的依赖关系大大减弱.当辐照注量为8.0 × 1010 ions/cm2时,潜径迹对磁通涡旋的钉扎效果最佳.在该注量下,高场(B > 0.3 T)下临界电流密度达到最大值且钉扎力提升了近两倍,临界转变温度无明显变化(△Ton ≈ 0.5 K).实验结果表明,快重离子辐照产生的潜径迹可以在不影响临界转变温度的前提下有效改善磁场下超导载流能力.YBa2 Cu3 O7-δ(YBCO)high temperature superconductor materials have many promising applications in energy,transportation and so on.Nonetheless,the application of YBCO in high magnetic field was limited because of low critical current.One-dimensional latent tracks produced by swift heavy ions irradiation can be effective pinning centers,thus enhancing superconductivity in external field.YBCO high temperature superconducting films were irradiated with 1.9 GeV Ta ions at room temperature and vacuum condition.Structure damages in irradiated samples were characterized by transmission electron microscopy(TEM).Continuous amorphous latent tracks,with diameter from 5 nm to 15 nm,throughout the whole superconducting layer can be observed from TEM images.Physical property measurement system(PPMS)was used to measure superconducting properties of samples before and after irradiation.When irradiated at optimal fluence of 8 x1010 ions/cm2,critical current reaches its maximum value and pinning force was twice of unirradiated sample,while critical temperature almost unchanged.The analysis of experimental results shows that latent tracks produced by swift heavy ions irradiation can enhance in-field current-carrying capability,without decreasing critical temperature.In the power-law regime Jc∝B-αvalues of a decreased with the increasing of fluence,indicating a weaker magnetic field dependence of critical current.a reaches its lowest value 0.375 when irradiated at a fluence of 5.0×1011 ions/cm2,corresponding to a lowest in-field Jc.This result may be a combination of increasing pinning centers and decreasing superconductor volumes that work together.Normalized pinning force fp=Fp/Fp,max of sample irradiated with different fluence as a function of magnetic field h=H/Hmax was analyzed using Higuchi model.Fitting results show that planar defects are main source of pinning when h>1 independent of irradiation.Whereas,dominate pinning centers shifting from surface pinning to isotropic normal point pinning with increasing fluence when h

关 键 词：YBCO高温超导薄膜 快重离子辐照 钉扎 

分 类 号：TB383.2[一般工业技术—材料科学与工程] TM26[电气工程—电工理论与新技术]