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

YBa2Cu3Ox(YBCO)长期以来一直被认为是下一代77K超导导体的候选材料。为了利用YBCO材料的高性能，在金属衬底上使用高度织构的氧化物缓冲层，广泛地进行了YBCO带材的试制。由于YBCO的晶体各向异性大，相干长度短，晶界的影响是显著的。多晶材料通常用于制造长带材，因此晶界J_c的抑制成为一个很大的问题。为了最大限度地利用YBCO的高性能，发展将YBCO薄膜晶界角控制在10度以下的双向取向技术是必要的。为了解决这一问题，我们制备了双轴织构的Ni和Ni-Cr带材，并用…研究了脉冲激光沉积在带材上沉积的CeO_2薄膜的晶体取向和微观结构门禁更严了。再结晶的Ni-Cr带材具有立方织构，具有{100}&lt；001&gt；取向，其表面被(100)择优取向和强烈的面内取向占据。尽管再结晶Ni带具有{100}&lt；001&gt；织构，且后续沉积的CeO2薄膜也具有(100)取向，但在脉冲激光沉积过程中，CeO2薄膜的择优取向受氧分压的影响，且CeO2薄膜的(100)取向程度随薄膜厚度的增加而提高。此外，我们还测量了J_c的磁场角度关系，并研究了YBCO薄膜的磁通钉扎特性。证实了衬底材料和沉积温度对YBCO薄膜中晶体缺陷引入的影响，导致J_c随场的角度变化不同.结果表明，垂直于衬底中形成的位错对J_c有较大的影响.通过在金属衬底上的YBCO薄膜中引入高密度位错，获得了控制J_c的可能性.较少

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