直流溅射法制备YBCO带材研究

【作者】 肖山；

【导师】 张鹰；

【作者基本信息】 电子科技大学 ， 电子科学与技术， 2010， 硕士

【摘要】 YBCO高温超导带材具有优异的电学性能,它具有在外场下临界电流高,交流损耗低以及成本较低等优点,在工业应用中有非常大的潜力,所以各国都投入了巨大的人力物力进行研究。直流溅射具有方法简单、易于控制以及工艺重复性好等特点,本文基于直流溅射法研究了Y2O3种子层薄膜的制备工艺,并且在制备有Y2O3/YSZ/CeO2 (YYC)缓冲层的镍钨合金(Ni-5at.%W)基带上制备YBCO涂层导体进行了研究,还对YBCO薄膜的磁通钉扎特性也做了初步探讨。主要内容如下:1、根据c轴择优度和温度的关系以及反应溅射特有的迟滞效应,得出当温度为720℃,溅射电流为0.2A,水分压为0.016Pa,反应溅射处于平衡状态,制备出Y2O3种子层薄膜纯c轴取向,且面内面外半高宽为3.9°和4.9°。2、在Y2O3/YSZ/CeO2(YYC)缓冲层上制备YBCO涂层导体,发现缓冲层表面粗糙度对YBCO薄膜的性能有很大的影响,分别在反应溅射法和射频溅射法制备YYC缓冲层上以相同的工艺制备YBCO薄膜,两种缓冲层都是纯c轴取向,面内面外取向一致性相当,但反应溅射法制备的缓冲层粗糙度明显大于射频溅射制备的,在前者上制备的YBCO薄膜临界电流密度Jc为1.2 MA/cm2,而在后者基础上制备的YBCO薄膜的临界电流密度Jc达到2.8 MA/cm2。3、探讨了用卷绕法在平面靶直流溅射装置上连续制备YBCO带材的工艺,780℃为卷绕法制备YBCO薄膜的适宜温度,由于平面靶的负离子反溅射效应较为明显,综合考虑靶基距和气体总压,并且通过改变卷绕速度,补偿由于负离子反溅射效应导致的成分偏差,在靶基距为20mm,气体总压为70Pa,卷绕速度为0.55m/h时,临界电流密度达到0.6MA/cm2。4、研究了YBCO超导薄膜在磁场下的性能变化,首先在65K和77K的温度下,外加0-2T的磁场下对未掺杂的YBCO薄膜的性能进行测试,磁场方向垂直于基片表面,温度越低,YBCO薄膜的性能随磁场强度的增大下降的趋势越弱,然后我们还用Y过量的靶制备了富Y的YBCO薄膜,由于Y2O3在YBCO薄膜中形成钉扎中心,其在磁场下的性能明显优于未掺杂的YBCO薄膜。更多还原

【Abstract】 YBa2Cu3O7-δ(YBCO) superconducting tapes have promising electronic and electric applications ,because of its the high critical current density (Jc) in external magnetic fields, lower ac loses and processing costs. YBCO HTS tapes (also called coated conductors) attract the attention of the researchers worldwide. In this thesis, YBCO coated conductors were deposited on Y2O3/YSZ/CeO2(YYC) buffered Ni-5at.%W substrate with sputtering because it is easy to control and high reliability. The main content of this thesis including:1. According to the relationship between temperature and c-axis textured orientation of Y2O3 seed layer, the optimal temperature was obtained. And then we studied the optimal water partial pressure according to the hysteresis characteristic of the reactive sputtering. The Y2O3 seed layer film with pure c-axis orientation was deposited under the condition of the temperature being 720℃, sputtering current being 0.2A and water partial pressure being0.016Pa.The full width at half maximum(FWHM) of in-plane and out-of-plane scan are 3.9°and 4.9°.2. The surface roughness of the Y2O3/YSZ/CeO2 (YYC) buffered layer has a great influence to the quality of the YBCO coated conductors. The YYC buffer layers which were prepared by reactive sputtering and the RF sputtering were pure c-axis orientation , and the FWHM of in-plane and out-of-plane scan were similar, but the root mean square (RMS) roughness of the YYC that prepared by reactive sputtering is significantly greater than that of YYC prepared by RF sputtered, As a result, the critical current density of YBCO thin film that deposited on the former buffer layer was 1.2 MA/cm2, but that of YBCO thin film on the latter reached 2.8 MA/cm2.3.The fabrication of YBCO by reel-to-reel technology has been studied, the optimal temperature is 780℃. Because the negative ions bombardment effect of the plane target was obvious, we changed the speed of the reel-to-reel to compensate the component deviation. The critical current density of YBCO thin film reached 0.6 MA/cm2 under the condition that the distance between target and substrate was 20 mm, the total gas pressure was 70Pa and the speed of the reel-to-reel was 0.55m/h. 4.The performance of the YBCO coated conductors in magnetic field had been studied,we applied magnetic field of 0-2T that is perpendicular to the substrate surface at the 65K and 77K, found that the YBCO films with Y2O3 particles, pinning centers have showed substantial improvement in comparison with pure YBCO films in magnetic field.更多还原