Microstructures of High-<tex>$rm T_c$</tex>Superconducting Films Having Artificial Pinning Centers

Abstract

REBa/sub 2/Cu/sub 3/O/sub 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/sub c/. However, the J/sub c/-B characteristics of REBa/sub 2/Cu/sub 3/O/sub y/ films have a magnetic field angle dependency. When the magnetic field is applied parallel to the film surface, the reduction in J/sub 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/sub 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/sub c/ superconductors, it is important to improve the J/sub 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/sub 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.