【作者】 孙瑞萍；

【导师】 蒲明华；

【作者基本信息】 西南交通大学 ， 材料学， 2008， 硕士

【摘要】 第二代高温超导带材材料REBa₂Cu₃O_x（简写成REBCO,RE为钇或镧系元素）,由于其优良的本征电磁特性,尤其是其在高磁场下优良的载流能力,在电力系统中拥有广阔的应用前景,成为近年来研究的热点和超导技术发展的重点。而制备过程中直接在柔性金属NiW基带上制备YBCO涂层导体存在严重的晶格失配和互扩散问题。目前的高温超导涂层导体都具有衬底、缓冲层（至少一层）和REBCO超导涂层三层结构。在NiW基带衬底和REBCO超导薄膜之间的缓冲层材料,既要充当从NiW基带到REBCO外延生长的中间模板,又要阻挡两种材料的相互扩散主要是Ni和REBCO中的Cu的相互扩散。本论文基于涂层导体实用化的要求,主要研究涂层导体用新型缓冲层稀土铋氧（REBiO₃）的化学制备方法。为了研究此新型缓冲层的外延工艺,首先以外延性能良好、表面平整且性能相对稳定的LaAlO₃/SrTiO₃单晶片为衬底,进行研究,对材料的生长工艺、结构、性能进行了较为深入的研究和探讨,并开发了快速低成本的制备技术;之后在NiW基带上外延了此新型缓冲层。主要内容如下:1、涂层导体概述和制备方法,着重介绍了化学溶液沉积和外延生长机理;2、介绍了新缓冲层材料REBiO₃的晶体结构、电性质、磁性质和抗腐蚀性,证明此材料可以充当涂层导体的缓冲层;3、采用两种化学溶液沉积的制备技术在单晶片LaAlO₃/SrTiO₃上外延新型缓冲层稀土铋氧（REBiO₃）,研究了其制备工艺,并讨论了样品性质:（1）利用含水高分子辅助化学溶液沉积（PACSD）方法沉积REBiO₃薄膜,对薄膜的织构、微结构进行表征,并在其上利用自行开发的基于金属乙酸盐的高分子辅助无氟金属有机物沉积（MOD）技术制备了YBCO超导层;（2）利用无水高分子辅助化学溶液沉积方法（PACSD）沉积REBiO₃薄膜,通过对比可以看出,无水方法制备的REBiO₃薄膜在织构性、致密度和平整程度方面都比含水方法的好,另外对后续的YBCO超导层的生长诱导作用也比较强。（3）以DyBiO₃为例,分别在空气中和普通氩气（99.99%）中研究了REBiO₃的成相工艺,通过一系列的实验比较了样品的织构和微观形貌,判断出两种环境下样品的最佳成相温区。4、利用无水的PACSD法制备了传统缓冲层CeO₂,并通过稀土元素的掺杂提高了其临界厚度。5、采用无水PACSD法在Ni-5%W合金基带上外延了REBiO₃缓冲层:（1）改善和细化了原始的镍基带自氧化外延生长织构NiO薄层的工艺;（2）利用高分子辅助沉积技术在表面自氧化的Ni-5%W合金基带上沉积REBiO₃缓冲层,得到了双轴织构、表面致密平整的REBiO₃,为YBCO（MOD）/REBiO₃（MOD）/NiO（SOE）/NiW结构中后续的YBCO超导层的生长做了有利的铺垫。更多还原

【Abstract】 Due to the excellent intrinsic electromagnetic characteristics, especially can carry high electric currents in high field magnets, the second generation HTS’s REBa₂Cu₃O_x （REBCO） are now attracting much attention in recent years which have widely application prospect. The most significant problems to grow YBCO-coated conductor on NiW tapes are the lattice misfit and the Ni diffusion. A buffer layer is necessary to prevent Ni diffusing and provide a template for the subsequent growth of the YBCO superconducting layer.In this thesis, we deposition the new series of buffer layers REBiO₃ for the coated conductor by chemical preparation approach which offers a large-scale way for the practical applications of coated conductors. To study on the technique of the heat-treatment, we firstly choose single crystal flakes like LaAlO₃/SrTiO₃ as the substrates, then deposit buffer layers on the Ni-alloys tapes. The single crystal substrates with smooth surface and good epitaxy may provide relatively stable template.The major contents are as follows:1. Significant scientific as well as practical interests of the coated conductor research have been introduced, and the fabrications of buffer layer have been studied, especially the chemical solution deposition and the epitaxial growth mechanism.2. The crystal structure, electrical and megnetic properties, and the stability of new buffer layers REBiO₃ have been clarified.3. We studied the fabrication technology of REBiO₃ deposited on single crystal substrate LaAlO₃/SrTiO₃ using different chemical solution deposition.（1） REBiO₃ buffer layers have been deposited on single crystal substrate LaAlO₃/ SrTiO₃ by aqueous polymer-assisted chemical solution deposition （PACSD）. YBCO layer has been deposited on YBiO₃/LaAlO₃ by our newly developed fluorite-free MOD and a critical current density J_c （77K, OT） over 3MA/cm² has been obtained with a transition temperature at 90K.（2） A comparison between aqueous polymer-assisted chemical solution deposition （PACSD） and non- aqueous PACSD approaches have been performed, indicating that REBiO₃ thin films with better quality have been obtained via the non-aqueous PACSD approach and the non-aqueous approach itself is of better stability.（3） The epitaxial growth of DyBiO₃ on single crystal substrate has been studied. The influence of the thermodynamic parameters on the phase structure, texture as well as microstructure has been investigated.4. Fabricate REBiO₃ on Ni-5%W alloy tapes by non- aqueous PACSD approach:（1） The process of surface-oxidation epitaxy has been improved;（2） Textured, dense, and smooth REBiO₃ buffer layers have been deposited on Ni-5%W tapes by the non-aqueous PACSD, it is favorable for the subsequent deposition of YBCO in the new structure of coated conductors i.e. YBCO （MOD）/REBiO₃ （MOD）/NiO （SOE）/ NiW.5. Deposit CeO₂ on NiW tapes using the non-aqueous PACSD approach as well as improve the critical thickness of CeO₂ by doping RE elements.更多还原