Applications of superconducting oxides in magnetic field include many difficult problems to be solved. Especially, anisotropy both in the upper critical field Bc2 and the critical current density Jc, which originates from the lower symmetry of their crystal structures, will become crucial. Moreover, flux creep problems in relation to transport phenomena in magnetic field are under discussion. Recently, Jc values of the superconducting oxides have been rapidly improved with the progress in fabrication processes, for example, epitaxial and textured growth methods. In the case of Y1Ba2Cu3O7-δ films, the Jc values at 77.3K in magnetic field perpendicular to c-axis have been reported so far to be Jc(27T)=6.5×104A/cm2 for a specimen by CVD process, Jc(7.5T)=5×104A/cm2 by laser ablation, Jc (15T)≈6×105A/cm2 by electron beam evaporation, and Jc(20T)=1×104A/cm2 by sputtering. In this review paper, the problems on critical current densities of superconducting oxides are discussed and the fabrication processes which will attain higher Jc are summarized.
