Preparation Of Buffer And Superconducting Layers For Coated Conductors By Polymer Assisted Chemical Solution Deposition Methods

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.