Fabrications and characterizations of electrical and mechanical properties of high $T_C$ superconducting tapes on textured metallic substrates

Abstract

Ni tapes were textured by taking advantage of their secondary recrystallization. The tapes were single crystalline with their [001] axes tilted with respect to the surface and their [100] axes parallel to the rolling direction. The reproducibility of this method, the application to NiCr tapes to improve stiffness, and the possibility of c-axis normal $YBa_2Cu_3O_{7-δ}$ film growth on those tapes were studied. %We took statistics on the crystal orientations of 24 Ni tapes. We obtained a NiCr (13 atomic%) tape by diffusion of Cr atoms, and fabricated coated conductors on this substrates. $CeO_2$/YSZ/$CeO_2$ buffer layers were deposited by e-beam evaporation and YBCO overlayer was deposited by coevaporation. Resistivity and critical transport current density were anisotropic in the surface. Transition temperature was 86 K, and critical current density was $3×10^5~A/㎠$ at 77 K in the rolling direction. And we also grew c-axis normal YBCO films on tilted textured Ni tapes by sputtering method. Tensile stress dependent critical current densities ($J_C$) of two types of coated conductors, which were fabricated on a pure Ni, a NiCr (13 atomic %) RABiTS tape and NiCr RATiS, respectively, were measured at 77 K. Until the stress reached a certain values ($K_C$), $J_C$ of each sample was constant, and then it began to decrease as the stress was increased more. $K_C$``s for those of Ni and NiCr were ~100 MPa and ~270 MPa, respectively, which means $K_C$ was almost three times enhanced for the sample fabricated on the NiCr. The $K_C$ for the coated conductors on NiCr RATiS were ~100 MPa, and degradation processes are somewhat different from coated conductors on RATiS. According to the detailed changes of voltage signals for applied currents under various stresses, the degradation process of each sample could be divided into four different regimes, and the process is disdussed in accordance with the crack formation. Magneto-resistances of the coated conductors fabricat...