Study On The Preformance Of Nano Particle Doped YBCO Film By Low-fluorine MOD Method

Since the discovery of high temperature superconducting material YBa₂Cu₃O_7-x?YBCO?,it has become a hotspot in the area,due to its advantages in superconducting performances compared to Bi superconductors.The critical current of the YBCO coated conductor is determined by the following two aspects:the critical current density of the coated conductor and the thickness of the YBCO film.The larger the critical current density and the thickness of the YBCO film,the greater the critical current of the superconducting tape.In order to improve the current carrying capacity of YBCO film,this paper studied the relationship between the film thickness and the properties of YBCO films prepared with high-pinning Zr-doped YBCO films.Then,YBCO films doped with 6%LAO were preliminarily studied,and the superconducting properties of La AlO₃?LAO?and BaZrO₃?BZO?co-doped YBCO films were studied on the basis of these results.The results obtained are as follows:Firstly,using the improved heat treatment process?multiple low temperature heat treatment+one time of heat treatment?,BZO/YBCO composite films with thickness of 200nm?monolayer?,400nm?double membrane?,600nm?three film?and 800nm?four film?were prepared on LaAlO₃ substrate,respectively,by a single,two times,three times and four times of coating,and a detailed study of the BZO/YBCO composite films under different film thickness,surface morphology and microstructure of the superconducting properties has been carried out.By studying the relationship between the thickness of YBCO composite film and the critical current,the following results were obtained:the improved heat treatment process effectively eliminated the interface.When the thickness of the composite film is not more than600nm,the critical current keeps increasing with the increase of the thickness of the composite film.Among them,the J_c value of monolayer film was the largest,reaching3.34MA/cm².The J_c value of three layer film was reached to 1.91 MA/cm²,and its I_c value was the largest,reaching a bandwidth of 114.6A.Secondly,through investigation to the superconducting properties of LAO doped YBCO thin films,we found that the critical current density of 6%LAO/YBCO composite film reached 4.1MA/cm²,which showed that the 6%LAO/YBCO thin films had got good superconducting properties.Finally,the influence of the doping amount of LAO nanoparticles on the properties of double doped?LAO+BZO?/YBCO composite films were investigated.It was found that the?2%LAO+6%BZO?/YBCO,?4%LAO+6%BZO?/YBCO,?6%LAO+6%BZO?/YBCO,?8%LAO+6%BZO?/YBCO composite films have higher micro stress than that of pure YBCO films.In self field,the critical current density of this four composite films reached 3.39MA/cm²,3.48MA/cm²,3.30MA/cm² and 2.44MA/cm²,respectively.The critical current density of?4%LAO+6%BZO?/YBCO composite film is the largest,and at 77K,1T,performance of this double doped film is better than that of the single doped composite film.In summary,through the research on the effect of thickness on the critical current of BZO/YBCO composite film,and the influence of doped LaAlO₃ and BaZrO₃nanoparticles on the field properties of?LAO+BZO?/YBCO thin films,we found that BZO/YBCO composite film with 600nm thickness got the maximum critical current.?LAO+BZO?/YBCO composite film with 4%LAO and 6%BZO doping content got the maximum critical current density,and at 77K,1T,performance of this double doped film is better than that of single doped composite film,indicating that the critical current of YBCO thin films can be effectively increased by increasing the film thickness and double doping of nanoparticles,so as to meet the needs of practical applications.