YBCO超导带材缓冲层的生长控制研究

发布时间：2018-07-02 10:05

本文选题：YBCO超导带材 + CeO_2/YSZ/Y_2O_3缓冲层　；参考：《电子科技大学》2014年博士论文

【摘要】：以YBa2Cu3O7-δ(YBCO)为代表的第二代高温超导带材具有优异的电学性能,在电力传输、电能存储、强磁场等领域有着非常广阔的应用前景。为获得高性能的YBCO超导带材,必须制备出高质量的缓冲层来传递双轴织构以及阻挡基带和超导材料间的互扩散。目前在制备过程中仍然存在大量的瓶颈问题需要解决:如晶粒间夹角的控制、新型缓冲层结构的选取和制备、成本的降低等。本论文基于轧制辅助双轴织构(RABiTS)路线,从薄膜的生长工艺入手,对薄膜织构、表面形貌的调控机制以及缓冲层对超导薄膜载流能力影响的机理开展了系统的研究工作。主要内容如下:1、采用直流磁控反应溅射法在双轴织构的Ni-5at.%W(NiW)基带上制备双面CeO2/YSZ/Y2O3薄膜,通过调整水分压、溅射气压和沉积温度等工艺条件,进行了三层缓冲层结构的生长控制研究。在最优工艺条件下制备的Y2O3薄膜面外织构为1.5o,面内织构为4.8o,表面均方根粗糙度Rrms为2 nm。并通过对Y2O3薄膜应力变化与薄膜生长机理的分析,建立两种生长模型阐述Y2O3薄膜面外织构大幅度改善的原因。采用溅射原子扩散、成核的理论模型对CeO2薄膜表面形貌及晶粒变化进行了理论分析,并结合工艺实验实现了平整致密模板层的制备,表面均方根粗糙度Rrms小于3 nm。为制备高质量的YBCO带材提高了保证。2、利用超导电流在YBCO中传输模型计算了晶界夹角对YBCO薄膜载流能力的影响,并通过对比在具有不同织构缓冲层样品制备YBCO薄膜的临界电流密度,从实验上对计算结果进行验证。进行了对缓冲层表面形貌对YBCO载流能力影响的规律进行研究,选取不同表面形貌的CeO2/YSZ/Y2O3缓冲层,在其上采用相同的工艺制备YBCO薄膜,利用高分辨X射线衍射谱计算不同样品的螺型位错与刃型位错密度,理论分析了不同表面粗糙度对YBCO位错密度的影响,对比不同样品YBCO薄膜的临界电流密度,解释了缓冲层表面粗糙度对YBCO薄膜临界电流密度影响的原因。最后在最优双面多层缓冲层上制备的YBCO薄膜双面临界电流密度Jc一致,双面临界电流Ic值为500 A/cm-width。3、为了解决直流溅射中靶材中毒导致沉积速率下降的难题以实现缓冲层的快速高质量制备,采用交流中频磁控反应溅射制备Y2O3种子层,研究中频电压、溅射气压对Y2O3薄膜取向和表面形貌的影响规律。Y2O3种子层制备效率提高到直流溅射的3倍,从5 m/h的制备效率提升到15 m/h,甚至最高可达到50 m/h,这对于YBCO超导带材的工业化具有非常重要的意义。在中频溅射制备的Y2O3薄膜上成功制备了良好的面内外织构的YSZ阻挡层和CeO2模板层,进一步证明了中频磁控反应溅射技术能够快速制备高质量缓冲层的优点。4、简化缓冲层制备工艺以降低工艺成本,并提高带材的工程实用性,提出了全导电TiN/SrRuO3(SRO)缓冲层新结构,并采用脉冲激光沉积技术进行了验证。研究不同制备工艺下TiN种子层的生长规律,XRD测试结果表明TiN和SRO具有良好的面内外织构,SRO表面粗糙度Rrms小于5 nm。I-V曲线测试全导电缓冲层SRO/TiN在常温具有良好的导电特性。在其上采用直流溅射法制备YBCO薄膜,R-T曲线表明采用全导电缓冲层的超导带材在转变温度附近电阻率仅约为2×10-5Ω?cm。全导电缓冲层结构为YBCO超导带材缓冲层技术提出了新的途径。
[Abstract]:The second generation high temperature superconducting strip, represented by YBa2Cu3O7- Delta (YBCO), has excellent electrical properties. It has a very broad application prospect in the fields of power transmission, electric energy storage and strong magnetic field. In order to obtain high performance YBCO superconducting strip, high quality buffer layer must be prepared to transfer biaxial texture and block the base band and superconducting material. A large number of bottlenecks still exist in the process of preparation, such as the control of the angle between grains, the selection and preparation of the new structure of the buffer layer, and the reduction of the cost. This paper is based on the rolling assisted dual axis texture (RABiTS) route, starting with the growth process of the film, and regulating the texture and surface morphology of the film. The mechanism of the effect of the system and the buffer layer on the current carrying capacity of the superconducting thin film is systematically studied. The main contents are as follows: 1, the two-sided CeO2/YSZ/Y2O3 film is prepared on the Ni-5at.%W (NiW) base band of the dual axis texture by DC magnetron sputtering, and the three layers are carried out by adjusting the water pressure, the splash pressure and the deposition temperature. The growth control of the buffer layer structure. The surface texture of Y2O3 thin film prepared under the optimal process conditions is 1.5o, the texture in the surface is 4.8o, the surface RMS roughness is 2 nm., and the two growth models are set up to explain the reason for the large improvement of the texture of the Y2O3 film through the analysis of the stress change of the Y2O3 film and the growth mechanism of the thin film. The theoretical model of the surface morphology and grain change of CeO2 thin film by sputtering atom diffusion and nucleation is theoretically analyzed, and the preparation of the smooth and dense template layer is realized with the process experiment. The surface RMS roughness is less than 3 nm. for the high quality YBCO strip to be prepared, and the.2 is improved and the superconducting current in YBCO is used to transfer the model. The influence of the grain boundary angle on the current carrying capacity of the YBCO film was calculated. By comparing the critical current density of the YBCO thin film with different texture buffer layers, the results were verified experimentally. The rules of the influence of the surface morphology of the buffer layer on the YBCO current carrying capacity were studied, and the CeO2/YS of different surface morphology was selected. The Z/Y2O3 buffer layer is used to prepare the YBCO thin film on the same process. The snail dislocation and the edge dislocation density of different samples are calculated by high resolution X ray diffraction. The influence of different surface roughness on the dislocation density of YBCO is theoretically analyzed. The critical current density of different samples of YBCO films is compared, and the surface roughness of the buffer layer is explained. The reason for the influence of the critical current density on the YBCO film. Finally, the two side critical current density (Jc) of the YBCO film prepared on the optimal double-sided multilayer buffer layer is consistent, and the double side critical current is 500 A/cm-width.3. In order to solve the difficult problem of the deposition rate of the target poisoning caused by the direct current sputtering, the rapid and high quality preparation of the buffer layer is achieved. Y2O3 seed layer was prepared by AC medium frequency magnetron sputtering, and the effect of medium frequency voltage and sputtering pressure on the orientation and surface morphology of Y2O3 thin film.Y2O3 seed coating efficiency was increased to 3 times of DC sputtering, the preparation efficiency from 5 m/h to 15 m/h, or even up to 50 m/h, for the industrialization of YBCO superconducting strip. It is very important that a good YSZ barrier layer and CeO2 template layer are successfully prepared on the Y2O3 thin film prepared by medium frequency sputtering, and the advantages of the medium frequency magnetron reactive sputtering technology can be further proved to be able to quickly prepare the high quality buffer layer,.4, to simplify the preparation of the buffer layer to reduce the process cost and to improve the engineering of the strip. Practicality, a new structure of fully conductive TiN/SrRuO3 (SRO) buffer layer was proposed and verified by pulsed laser deposition. The growth law of TiN seed layer under different preparation processes was studied. The results of XRD test showed that TiN and SRO had good texture in and out of face, and the surface roughness Rrms of SRO was less than 5 nm.I-V curve to test all conductive buffer layer SRO/Ti. N has good electrical conductivity at normal temperature. The YBCO thin film is prepared by direct current sputtering on it. The R-T curve shows that the resistivity of the superconducting strip near the transition temperature is only about 2 x 10-5 Omega. The structure of the full conductive buffer layer of the YBCO superconducting strip is a new approach to the buffer layer technology of YBCO superconducting strip.
【学位授予单位】：电子科技大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM26

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