Microstructures of high-Tc superconducting films having artificial pinning centers

REBa₂Cu₃O_y (REBCO) is expected to be used in numerous applications, such as power transmission cables, high-field magnets and generators, due to the possibility of a high critical current density at 77 K under a high magnetic field. Biaxially textured REBCO superconducting tapes are developed to obtain high-J_c. However, the J_c-B characteristics of REBa₂Cu₃O_y films have a magnetic field angle dependency. When the magnetic field is applied parallel to the film surface, the reduction in J_c is not larger under a high magnetic field of 10 T. When the magnetic field is applied perpendicular to the film surface, the reduction in J_c is significantly large under a magnetic field of more than around 5 T at 77 K. From the viewpoint of realizing wide applications of high-T_c superconductors, it is important to improve the J_c-B characteristics of REBCO films under magnetic fields higher than 5 T applied perpendicular to the film surface. Our group focuses on artificial pinning centers (APCs) introduced into REBCO films. The J_c-B characteristics of certain films are improved by the introduction of APCs. The microstructures of these films are investigated using transmission electron microscopy (TEM). We report on the microstructures of REBCO films with APCs.