MOCVD Process Investigation Of Superconductive Layer Of Zr-doped YBCO Coated Conductors

In recent years,high performance YBCO superconducting tapes,as the representative of the second generation high temperature superconducting tapes,have been widely studied,which have important application value in the high field magnet,large current transport and so on.Due to the characteristics of high deposition rate and good crystal quality,MOCVD technology has been widely used in the growth of semiconductor devices.It is a very challenging field to grow high temperature superconductiviting layer and has a very important significance for YBCO strip commercialization.In this paper,LaMnO3/homo-epi MgO/IBAD-MgO/SDPY2O3/Hastelloy alloy was used as the substrate base of YBCO superconducting layer,and the MOCVD technology was used to study the superconducting thin film process.The main contents of the study include the following aspects:1 MOCVD processing technology of YBCO Superconducting layer is carried out from the ratio of three metal organic source,substrate temperature and film thickness of these aspects.The research indicates the increase of Y(tmhd)3 content in a certain range has little effect on the oriented growth of YBCO film,but it can improve the flatness of the surface of YBCO film effectively.The increase of Ba content could increase the growth of the a-axis crystalline grain in the film and decrease the critical current density.Increasing the proportion of Cu in organic sources will not only reduce the pores on the film surface and improve the film density,but also lead to the increase of a-axis grains and the reduction of Jc value.The result of temperature experiment is obtained by analyzing the structure and morphology of the films prepared under different heating currents.When the heating current is low,the a-axis grains exist in the film.The increase of temperature can make the film orientation be better,but when the temperature is too high YBCO will decompose to producing heterogeneous phase,also the density and orientation of the film structure will be deteriorated.When the heating current is 26.0A,Jc is the highest,reaching 4.0MA/cm2.With the increase of film thickness,the texture of the film becomes worse and the defects increase,in the meantime,the a-axis and caxis crystalline grains mixed growth,and the compactness is also poor.These factors can lead to the decrease of the critical current density.2 The study of flux pinning effect includes the effects of Gd and Zr doping on YBCO film.It was found that the diffraction peak of GdYBCO shift to low angle,and in-plane texture become worse with the increase of the Gd doping content,the a-axis peak emerges.When the Y/Gd molar ratio is 1: 1,the critical current density without the field reaches the maximum,Jc = 3.8MA/cm2,which is higher than the Jc value of the pure YBCO under the same process conditions.In addition,the YBCO thin film with 15% Zr doping content is better than 10% thin film about the flux pinning effect,and the decay is slower with the increase of magnetic field.