| Coated conductor is hot in current study on international high-temperature superconducting materials, but there is a bottleneck in its industrialization and large-scale application, i.e. the lack of a preparation process with high efficiency and low cost, particularly the lack of a buffer layer preparation process which is a key problem requiring urgent settlement.Aiming at a preparation process with low cost, continuity and easy industrialization, this paper provides two available schemes for coated conductor framework:one is to prepare NiO(200)/SmBiO3double buffer layers at about800℃with low cost. Such preparation process of NiO(200) buffer layer in argon atmosphere is our innovation for which patent protection has been applied for and SmBiO3buffer layer with independent intellectual property right is also independently developed by this research team, so SmBiO3/NiO(200)/NiW double buffer layer technique offers a unique and low-cost framework approach for the preparation of coated conductor. The other is to firstly optimize process parameters of short samples of RE:CeO2buffer layer prepared by using the Polymer Assisted Chemical Solution Deposition (PACSD) method combined with spin coating technique, then on such basis, to study Sm0.2Ce0.8O1.9preparation process with combination of PACSD method with dip coating technique, and finally to study the coating preparation technique of SCO polycrystalline wet film by combining PACSD method with slot-die coating. Based on the static heat treatment process, a dynamic continuous preparation system of high-temperature superconducting coated conductor tape is independently developed, designed and manufactured. On the basis of this system, a dynamic continuous preparation process of SCO/NiW buffer layer long tape is developed. Considerable progress has been made in the technique of preparing buffer layers by the PACSD method, i.e. from static preparation of short samples to dynamic preparation of long tapes. With the first preparation of high-quality buffer layer tape using chemical solution deposition method, it provides good technical reserves for future large-scale coated conductor industrialization.This paper mainly includes the following outcomes:I. A technique of preparing NiO(200) buffer layer by oxidization and epitaxy method.NiO(200) buffer layer with a thickness of5μm has been successfully prepared at800℃in ordinary argon atmosphere.The NiO(200) buffer layer film has bi-axial texture with compact and smooth surface, without micro-crack, featuring better adherence and more uniform thickness compared with those of the reported film prepared at high temperature of more than1000℃. SmBiO3buffer layer has been also successfully deposited on the NiO(200) buffer layer with the use of Polymer Assisted Chemical Solution Deposition (PACSD) method. The SmBiO3buffer layer film has bi-axial texture with compact and smooth surface, without micro-crack. The newly developed SmBiO3/NiO(200)/NiW combined double buffer layers offer a unique and low-cost structure approach for the preparation of coated conductor.Ⅱ. Optimal preparation process of Smo.2Ce0.8O1.9(SCO) and Gd0.3Ce0.7O1.8(GCO) single buffer layers by spin coating method and the PACSD methodSCO single buffer layer having a thickness of180nm and good texture with flat and compact surface is successfully prepared on Ni-5%W alloy tape, and optimal YBCO superconducting layer is prepared with the use of epitaxially deposited YBCO film above it, the superconducting transition temperature is Tc=87K and the critical current density may reach1.0MA/cm2at77K self-field. GCO buffer layer,180nm thick, has also been prepared. GBCO superconducting layer of sound performance is prepared with succeeded epitaxially deposition unto it, presenting a flat and compact film surface without micro-crack. The critical thickness of the CeO2buffer layer is increased by PACSD and mixing of rare earth ions, providing a new method for preparation of high-temperature superconducting coated conductors of single buffer layer.Ⅲ. A preparation process of SCO buffer layer by dip coating technique and the PACSD methodThe dip coating technique is more applicable to large-scale continuous preparation of long tapes of coated conductors compared with the spin coating method. Optimal preparation process parameters are obtained based on intensive analysis of such impact factors as sol concentration and withdrawal speed, including PAA10%; withdrawal speed:10mm/min; heat treatment in H2/Ar atmosphere at1100℃for0.5h. Such process is employed to obtain SCO sample, the film thickness may be up to250nm, and the film have good bi-axial texture with compact and smooth surface without micro-crack. YBCO superconducting layer has been prepared onto SCO by the fluorine-free MOD method and the dip coating technique, distinct (001) series peaks appear, and the YBCO film has completeness, compactness and no micro-crack surface.Ⅳ. A technique of preparing SCO buffer layer long tape by slot die technique and the PACSD methodA continuous preparation system of high-temperature coated conductor tape is researched, developed, designed and manufactured, which has independent intellectual property. On the basis of this system, a dynamic continuous preparation process of RE:CeO2buffer layer long tape is developed. Through intensive analysis on impact factors such as solution viscosity, tape moving speed, solution release speed, etc, optimal preparation process parameters are obtained, including polymer assisted solution PAA15wt.%, tape moving speed0.20m/h, solution release speed0.5ml/h. The die spacing shall be constant to enable a bead to be just full of a tape width. With respect to the SCO sample prepared with the use of this technique, it is150nm thick and has bi-lateral texture with more than90%integrity as well as impact and smooth surface without micro-crack, initiating the ability in preparation of high-quality buffer layer long tape with the use of fluorine-free chemical solution deposition method. |
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