【作者】 张欣；

【导师】 赵勇；

【作者基本信息】 西南交通大学 ， 材料学， 2013， 博士

【摘要】 涂层导体的制备技术和大规模工业应用是当前超导材料研究的热点。本论文基于涂层导体实用化进程中的织构优良,致密度高,载流能力强的要求,以涂层导体缓冲层和超导层的化学制备技术为研究对象,开发出了一系列低成本、高效率的制备高性能涂层导体的技术。通过对具有自主知识产权的REBiO3缓冲层材料的RE位进行掺杂获得了一系列新型的缓冲层材料,并得到了表面具有不同形状的纳米颗粒析出相的Sm0.5Ca0.5BiO3和Eu0.6Sr0.4BiO3缓冲层材料,取得了一些有意义的结果。论文第1章阐述了涂层导体研究开发的科学意义和实用价值,重点归纳与介绍了当前主流的缓冲层材料与制备技术。第2章系统地阐述了第二代高温超导带材(即涂层导体)的基本实验原理与方法。重点介绍了化学溶液沉积技术和外延生长机理。对该技术的分类、前驱物、制胶的工艺流程等进行了阐述。第3章对本论文涉及的实验方法和表征手段进行了阐述。实验方法方面,介绍了高分子辅助化学溶液沉积(PA-CSD)法制备涂层导体缓冲层与超导层的一般流程与相关技术参数。表征手段方面,对本论文涉及的相结构、微结构、电磁性能表征的手段进行了介绍。第4章重点介绍了SmBiO3缓冲层在单晶基底LaA1O3以及在NiO缓冲层上的PA-CSD法的制备技术。并且初步成功地完成了NiW/NiO (SOE)/SmBiO3(PA-CSD)/YBCO(PA-CSD)这种新颖与低成本的涂层导体结构的制备工作。随后介绍了一系列PA-CSD法制备传统缓冲层BaZrO3、SrZrO3、La2Zr207、以及导电缓冲层La0.7Sr0.3MnO3的技术,研究了各自的最佳热处理工艺路线。结合高分子添加剂的化学性质和热力学特性提出了一种解释单次涂敷临界厚度提高的机制。结果表明,高分子辅助沉积制备技术是一种成本低廉、易于推广的缓冲层制备技术。最后,在REBiO3缓冲层基础上,介绍了REBiO3中的RE位用Ca或Pb替代的研究工作。并据此在LaA1O3(100)单晶基底上制得织构良好、表面平整致密的Sm1-xCaxBiO3Eu1-xCaxBiO3、Gd1-xCaxBiO3、Gd1-xPbxBiO3外延薄膜,这为调节REBiO3的晶格和导电性提供了新的途径,并得到了一系列新型的缓冲层材料。此外,在本章中特别介绍了缓冲层材料Sm0.5Ca0.5BiO3和Eu0.6Sr0.4BiO3.在其表面可以制备出纳米级的不同形状的析出相,进而可能作为钉扎中心来研究其对YBCO涂层导体在磁场下的临界电流密度的影响。第5章讨论了EuBa2Cu3O7-x (EuBCO)薄膜在单晶基底LaA1O3(100)上的PA-CSD法的制备技术。利用自主开发的基于金属乙酸盐的高分子辅助无氟化学溶液沉积技术,在氮气气氛中LaAIOa (100)单晶基底上生长了EuBCO薄膜。通过对热处理过程进行优化,制得了厚度为290nm、双轴织构良好、表面致密平整和无微裂纹的EuBCO薄膜,且临界超导转变温度为91K,77K自场下的临界电流密度约为2.4MA/cm2。最后,对用PA-CSD法的制备超导薄膜的面内面外取向生长机理作了详细的讨论与解释。更多还原

【Abstract】 The fabrication techniques and the large-scale applications of coated conductors (CCs) are now attracting much attention. Based on the need of preparation of highly textured, dense CCs which can carry high electric current in practical applications, this dissertation aims at the chemical preparation approaches of the buffer layers and superconducting layer of CCs and develops a series of low-cost and high-efficient technology of fabricating high-quality CCs. Through Ca2+、Pb2+substitution of RE site with REBiO3buffer layer materials of self intellectual properties, a new series of buffer layers have been fabricated. In addition, the Smo.sCao.sBiO3and Euo.6Sro.4Bi03films with surface precipitated nano-particles of different shapes are fabricated and several meaningful results have thus been obtained.Chapter One elaborates the tremendous scientific and practical significance of the research and development of CCs and the currently prevailing buffer layers as well as their preparation approaches have been reviewed in detail.In Chapter Two, the fundamental research principle and methods of preparation approaches of the second generation superconducting tapes, i.e. coated conductors have been elaborated systematically, and the epitaxy mechanism of the buffer layers and superconducting layer of CCs has been introduced, and much attention has been focused on the chemical solution deposition (CSD) approaches of CCs. The classification, the flowing chart as well as the precursors have then been discussed.Chapter Three discusses the experimental details as well as the characterization approaches concerned in this project. As for the experimental method, the research for superconducting layer and buffer layer materials have been introduced, the polymer-assisted preparation approaches as well as the relating parameters for the preparation of superconducting layer, buffer layer have been discussed. As for the characterization, means of the characterization of the phase structure, microstructure as well as electromagnetic properties have been provided.In Chapter Four, the preparation of SmBiO3thin films on single crystal substrate LaA1O3as well as NiO buffer layer via polymer-assisted deposition route has been investigated and a new and low-cost fabrication of coated conductor NiW/NiO (SOE)/SmBiO3(PA-CSD)/YBCO(PA-CSD) is accomplished. And then a series of techniques of fabricating traditional buffer layers BaZrO3、SrZrO3、 La2Zr2O7and conductible buffer layer Lao.7Sro.3Mn03via PA-CSD route as well as their respective optimized thermal process route are introduced. To solve the problem of single coating critical thickness, a mechanism is put forward to explain the increase of the single coating critical thickness, combing the chemical and thermodynamic properties of polymeric additive and that all kinds of PA-CSD route help to increase the critical thickness of buffer layers is thus proved. The results show that the polymer-assisted chemical solution deposition technique of obtaining single buffer layer is easy to apply with low cost.Moreover, it is feasible to substitute RE position of REBiO3by Ca2+、Pb2+, and such as Sm1-xCaxBi03、Eu1-xCaxBiO3、Gd1-xCaxBiO3and Gd1-xPbxBiO3films with biaxially textured and fine microstructure have been obtained on LaA1O3(100) single crystal substrate, providing a new approach to modify the lattice parameters and conductivity of REBiO3.At last, Smo sCao.sBiO3and Euo.6Sro.4BiO3are introduced in particular, on whose surface the nanoscale precipitated phases of different shapes have been obtained and they can also be used as the potential pinning centers to research their impact on current density of YBCO coated conductors in magnetic field.In Chapter Five, the preparation of EuBa2Cu3O7-x(EuBCO) thin films on LaA1O3(100) single crystal substrate via PA-CSD technique is introduced. By applying homegrown polymer-assisted fluorine-free chemical solution deposition technology based on metal acetate, EuBCO thin films on LaA103(100) single crystal substrate is prepared in nitrogen. And the thermal process is optimized, an over290nm thick EBCO film with excellent biaxial texture as well as smooth and dense surface has been obtained by this method with Tc=92K, Jc=2.4MA/cm2at77K and self-field. Finally, the out-of-plane orientation and in-plane orientation growth mechanism of superconductive films by way of PA-CSD method is discussed in detail.更多还原