Preparation And Stress Mechanism Of Y_1-xGd_xBCO Thin Film With Gd Doping Prepared By F-free Metal Organic Deposition Method

In recent years,high temperature superconducting coated conductors have been widely used in the fields of power,information,transportation and so on,and have attracted much attention.Among them,the first generation of high temperature superconducting tape BSCCO coated conductor and the second generation high temperature superconducting tape YBCO coated conductor are the most outstanding superconducting series with industrialization prospect at present.Compared with BSCCO coated conductor,YBCO coated conductor has lower potential material cost and higher superconductivity.Therefore,YBCO high temperature superconducting material has attracted wide attention,become the focus of current research,and has high application value.However,the traditional preparation process has limited its rapid development due to factors such as production cost,environmental pollution and performance limit.And the‘thickness effect'caused by the increase of coating thickness leads to serious degradation of its superconductivity.Therefore,the MOD method is used to prepare YBCO coated conductors efficiently,and the stress regulation mechanism of YBCO coated conductors is studied by Gd doping to explore effective means to overcome the‘thickness effect'.The methods can prepare YBCO coated conductors by diversity.This paper take the fluorine free MOD method without high vacuum conditions,control components easily,prepare YBCO coated conductors on the substrate LAO.We optimized the preparation process parameters by adjusting the pulling speed,the times of coated layers and heat treatment temperature on the coated conductor to compare the influence of YBCO coated conductors,to get the better performance of YBCO coated conductors under the present experimental conditions.In order to overcome the‘thickness effect',a series of Y_1-xGd_xBCO thin films with different substitution ratios are prepared by fluorine-free MOD method deposited on a lanthanum aluminate?LAO?substrate.The growth orientation,microstructure and lattice vibration characteristics of the films are analyzed by X-ray diffraction?XRD?,scanning electron microscopy?SEM?and Raman spectroscopy.The results show that the lattice constant of the film and the orientation of the c-axis increases with the increasing Gd substitution ratio for x less than 0.5,and the increasing of tensile stress at the same time.However,with the further increase of Gd content,the structure of coated conductor will deteriorate and the performance will decrease.Our results indicate that the stress mechanism can be manipulated by controlling the content of various ionic radius in Y_1-xGd_xBCO films.The free standing film with optimal c-axis orientation can be obtained through proper substitution ratio,i.e.the ration of Y:Gd equaling to 1:1.These results suggest that manipulation of the stress mechanism is a promising method to overcome the‘thickness effect'effectively.