| REBCO bulk superconductors(RE is Y,Gd,Sm,Nd and other rare earth elements)have been widely used in many top technology fields such as the superconducting magnetic levitation,transportation system,energy storage flywheel,magnetic levitation bearing in recent years due to their large magnetic levitation force,magnetic flux capture ability and high critical current density.therefore,in order to satisfy the application needs,preparing high performance REBCO bulk superconductors is particularly important,and the research of growth rule of REBCO bulk superconductors for the preparation of high performance samples becomes more and more important,it has become the focus and hot spot of scientific research all around the world.In this process,there are still many scientific problems needs to be solved,such as the mechanism of YBCO crystal growth induced by NdBCO seed crystal with different grain orientations.This article uses the Y+011 TSIG method,use of the quenching process at 1100?,1008?,1006?,1004?,1002?,1000?,998?,996?,994?,992?,990? the eleven growth temperature isothermal 11 group YBCO bulk superconductors diameter of 20mm,each group of samples are induced by NdBCO seed crystal which ab face and ac face is perpendicular to the surface of the sample.The results show that the growth area of YBCO crystal increases with the decrease of supercooling degree.The specific studies on the growth rate and microstructure of YBCO bulk superconductor in this experiment are as follows:(1)study the change rule of YBCO crystal growth rate with supercooling degree induced by the NdBCO seed crystals which ab and ac surface perpendicular to the solid surface.It was found that the growth rate of YBCO crystal along axis a was always lower than that along axis c at the same supercooling degree.The growth rate along the a axis and the c axis of the sample surface was higher than that along the a axis and the c axis of the sample interior.(2)it was found from the study on the microtopography of samples placed parallel to and perpendicular to the solid surface on the ab surface of seeding crystals at different subcooling degrees.The grain orientation of NdBCO seed crystal determines the lamellar orientation of YBCO crystal.The Y211 particles captured by YBCO samples which is grown in 990? is more obvious than the YBCO samples which are grown in other supercooling degree and the Y211 particles near the growth front is smaller than the those near the leading edge of other samples grown in other supercooling degree.The number of Y211 particles captured by the sample increases with the increase of the supercooling degree.The farther the area from the seed crystal is,the more the number of Y211 particles is.This study is of great value for improving the crystal growth rate and properties of YBCO bulk superconductors.The YBCO bulk superconductors prepared by TSIG method have excellent performances in superconducting properties such as magnetic levitation force and magnetic flux capture.This experiment attempts to improve the production efficiency of YBCO by means of mass production.Firstly,1,3 and 7 YBCO samples were grown in the same batch.After the optimization of technical parameters,9 and 12 YBCO bulk superconductors were successfully grown in the same batch.By testing the magnetic levitation force of five batches of samples,the average magnetic levitation force can reach more than 100N.According to the analysis of the measured captured magnetic flux,the maximum capture magnetic field of the first batch of samples is 0.99t,and the average capture magnetic field distribution of the remaining four batches of samples is around 0.8T.By analyzing the microscopic morphology of the sample,a lot of Y211 particles were captured in the sample,and Y211 particles were dispersed evenly,and Y123 layers had good connectivity and no micro cracks appeared.These data fully illustrate that Y+TSIG method can be used to mass produce YBCO samples with excellent performance,which is of great significance for improving the production efficiency of superconducting blocks and promoting the practical application of YBCO superconducting blocks.YBCO superconducting ring was prepared.by Y+TSIG method.By comparing with YBCO bulk superconductor of equal diameter,the maximum magnetic field of YBCO superconducting ring was 0.56T,and that of the bulk superconductor was 0.98T.The magnetic levitation force of the superconducting ring is 58N,and the magnetic levitation force of the superconducting block is 102N.Therefore,it can be seen that the superconducting performance of YBCO superconducting ring is lower than that of the YBCO bulk superconductors,which is related to the appearance of tiny cracks on the sample surface.In the technical field that needs to be applied to the magnetic shielding properties of superconductors,YBCO superconducting ring has a broader application prospect compared with YBCO bulk superconductor.TSIG method can be used to prepare single-domain YBCO superconducting ring,but the technical parameters need to be improved to prepare high-performance YBCO superconducting ring. |
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