Orientation control of grain boundaries in high-temperature superconductors and elucidation of the superconductive curret flowing mechanism, The development of high-temperature superconductor tapes by the biaxial texturing using the cube textured Ni subst

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YBa_2Cu_3O_x(YBCO) has long been considered a promising candidate for next superconducting conductors operated at 77K. Trial of YBCO tape manufacture is widely carried out, to utilize high performance of the YBCO material, by using the highly textured oxide buffer layer on the metal substrates. Since the crystal anisotropy is large and the coherence length is short for YBCO, the effect of the grain boundary is remarkable. The polycrystalline substance usually is used for making the long length tape so that the suppression of J_c in the grain boundary becomes big problem. It is indispensable to develop the biaxial orientation technology which levels the grain boundary angle of YBCO films on the metal substrates in 10 degree or less for utilizing the high performance of YBCO maximally.In order to solve this issue, we have fabricated biaxial textured Ni and Ni-Cr tapes, and crystal orientation and microstructure of CeO_2 films deposited on the tapes by pulsed laser deposition were investi … More gated. Recrystallized Ni-Cr tapes had a cube texture, {l00}<001> orientation, and the surface of the tapes was occupied by the (100) preferred orientation and the strong in-plane alignment. Although recrystallized Ni tapes exhibited the {100}<001> texture and the CeO_2 films subsequently deposited on the tapes also have (100) orientation, the preferred orientation of CeO_2 films was affected by the oxygen partial pressure during pulsed laser deposition and the degree of the (100) orientation pf CeO_2 films was improved with increase of the film thickness. Moreover, we measured the magnetic field angular dependence of J_c and studied the flux pinning properties of YBCO films. We confirmed that the substrate materials and deposition temperatures have influences on the introduction of the crystalline defects into YBCO thin films, resulting in the different field angular dependence of J_c. The result shows that the dislocation perpendicularly formed in the substrate gives large effect in J_c. In this way, the possibility of controlling J_c was obtained by introduction of the high density dislocation into YBCO films on the metal substrates. Less