YBCO coated conductor の臨界電流の応力（ひずみ）効果に与えるバッファー層の影響

The stress and strain dependence of the critical current (Ic) was examined for YBCO-coated conductors with IBAD-CeO2/YSZ or ISD-MgO buffer layers. For all samples, Ic increased as the stress was increased and reached a maximum. For larger tensile stress, Ic started to decrease. The reversibility of Ic showed a different behavior depending on the buffer layer. For the tape buffered with IBAD-CeO2/YSZ, Ic recovered to the initial value after the applied strain reached 0.30%. On the other hand, a smaller reversible strain was observed for the ISD-buffered tape. The difference of the reversible strain was discussed based on a microstructure observation. For all samples, quenching occurred at a strain of more than 0.30%. Compared to the stress-strain curve of composite tapes, it was confirmed that quenching strains were determined by the yield strain of the Hastelloy substrate. The strain scaling law for the present YBCO-coated conductors was found to be similar to that for A15-type superconductors.