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

YBa_2Cu_3O_x（YBCO）一直被认为是下一代77 K超导体的理想候选材料。为了利用YBCO材料的高性能，通过在金属衬底上使用高度织构化的氧化物缓冲层，广泛地进行了YBCO带材制造的试验。由于YBCO的晶体各向异性大，相干长度短，晶界效应显著。由于多晶材料常用于制作长带，晶界处的J_c的抑制成为一个大问题。为了最大限度地发挥YBCO薄膜的高性能，必须发展双轴取向技术，使YBCO薄膜的晶界角在10 °或更小的范围内，为了解决这一问题，我们制备了双轴织构Ni和Ni-Cr带材，并研究了在其上用脉冲激光沉积CeO_2薄膜的晶体取向和微观结构。 ...更多信息 门控重结晶后的Ni-Cr带材具有立方织构，{100}<001>取向，带材表面为（100）择优取向和较强的面内取向。虽然再结晶Ni带具有{100}<001>织构，随后在其上沉积的CeO_2薄膜也具有（100）取向，但CeO_2薄膜的择优取向受脉冲激光沉积过程中氧分压的影响，随着薄膜厚度的增加，CeO_2薄膜的（100）取向程度提高。此外，我们还测量了YBCO薄膜的J_c随磁场角度的变化，并研究了YBCO薄膜的磁通钉扎特性。我们证实了衬底材料和沉积温度对YBCO薄膜中晶体缺陷的引入有影响，导致了不同的J_c随场角的变化关系。结果表明，垂直于衬底的位错对J_c的影响很大。这为在金属衬底上的YBCO薄膜中引入高密度位错来控制J_c提供了可能。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