Study Of The Flux Pinning Properties Of Bi-2212 Superconducting Films

High-temperature superconducting thin films have promising applications.But in practical applications,the critical current density of high-temperature superconducting films decreases due to the influence of ambient magnetic fields.It is important to improve the critical current density in the presence of magnetic field disturbances.Bi₂Sr₂CaCu₂O_8+δ（Bi-2212）high-temperature superconducting films contain no rare-earth elements,have an intrinsic Josephson effect and can be made into wires,making them the most promising for large-scale applications.However,the critical current density of Bi-2212 films decreases rapidly with increasing magnetic field,and this can be improved by improving flux pinning performance through elemental doping or particle irradiation.However,the experimental conditions for particle irradiation are harsh and have a large impact on the superconductivity,while elemental doping has a smaller impact on the films.In this paper,therefore,Bi-2212 thin films were prepared by sol-gel method with an excess of Bi elements.Lanthanum Zirconate（LZO）dot arrays of different sizes were prepared to further prepare LZO/Bi-2212 thin films.Investigate the effect of elemental doping and well-arranged arrays on the flux pinning performance of Bi-2212 thin films.The main studies and results are as follows:Bi-2212 films with excess Bi element added were prepared by sol-gel method（the excess Bi content was 1%,5%,10%and 15%respectively）.The XRD results showed that the biaxial texture of the films deteriorated with increasing Bi content and the R-T curves showed that the Tc values of the films decreased with increasing Bi content,successively at 81.4 K,80.8 K,79.8 K,77.6 K and 76.4 K.The variation of the critical current density with magnetic field was obtained by measuring the I-V characteristic curves of the samples at 50 K.It was found that the flux pinning performance of Bi-2212 films increased and then decreased as the doping amount increased,and the best flux pinning performance was obtained at 5%excess Bi element content.In order to further investigate the flux-pinning properties,LZO dot arrays of 50 mm and 25 mm in size were prepared by the photolysis-gel method,and Bi-2212 films embedded in the LZO dot arrays were further prepared.The XRD results show that the Bi-2212 films can be grown on LZO dot arrays with good c-axis orientation and biaxial texture.The R-T curves show that the Tc value of the films decreases as the size of the LZO dot arrays increases.The I-V curves of the samples at 50 K show that the LZO dot arrays can slow down the decay rate of Jc values with magnetic field.The M-H curve indicates that the broadening of the LZO/Bi-2212 composite film is significantly expanded,indicating that the flux pinning performance of the Bi-2212 film embedded in the LZO dot matrix is significantly enhanced.