The Study Of The Uniformity Of Long-length Coated Conductor's Buffer

Due to its high critical current density and high irreversible field,the second generation of high temperature superconducting tapes YBa₂Cu₃O_7-x?YBCO?has wide range of applications in many field,such as transmission cables,motors,current limiters,magnetic resonance imaging and magnetic levitation facilities.However,its commercial application is still limited by many conditions,such as high cost of fabrication,insufficient length of the tapes and insufficient uniformity of the the film.Therefore,this paper aims to fabricate MgO buffer layers for YBCO coated conductors with low cost,good uniformity and sufficient length on metal substrates.The main research contents are as follows:1.We fabricated Y₂O₃ amorphous thin film substrate,which is suitable for IBAD-MgO growth on the Hastelloy C276 substrate,using a solution deposition planarization?SDP?method.The effects of moving speed and heating temperature on the surface morphology and crystallinity of the amorphous films were studied.The original solution deposition platform system was improved.By adding the water cooling system and the dripping system,the time for the continuous preparation of the thin film was greatly shortened,thereby increasing the length of the tapes prepared.An amorphous thin film with a length of 440 m and a surface root mean square roughness?RMS?of 0.46nm-0.66 nm in a 5?m×5?m range was successfully prepared.For the preparation of the subsequent buffer layer,a substrate with a sufficient length and a smooth surface is provided.It has also been attempted to grow amorphous Y₂O₃ thin film on a lower cost X12CrNi177 stainless steel base tape having a width of 5 cm,reducing its RMS from 29 nm to 0.33 nm.2.The IBAD-MgO layer was prepared on the surface of the above-mentioned amorphous thin film by ion beam assisted deposition?IBAD?technology to provide a biaxial texture for the later YBCO thin film preparation.The effects of the plate voltage,tape speed,deposition rate,and ion beam flux on the film structure were studied.The matching of ion beam current and deposition rate was also discussed.A new multi-pass automatic flipping system was designed to fabricate double-sided IBAD-MgO with a single ion source single evaporation source,and the double-sided consistency was greatly improved.Epi-MgO film is epitaxially grown.The effects of epitaxial deposition rate and deposition thickness on the texture and mophology of the film were investigated.An epi-MgO/IBAD-MgO transition layer with a good texture uniformity of 30 m in length was successfully prepared.The out-of-plane full width at half maximum?FWHM?values is between 3.1 and 3.4°,and the in-plane FWHM values is between 5.0°and 5.8°.There is no significant difference between the two sides,which means the two-sided uniformity is good.