Non-monotonic reinforcement on the normal delamination strength of YBCO CCs at 20–293 K

Abstract YBa 2 Cu 3 O 7− δ (YBCO) coated conductors (CCs), with their multi-layered architecture and low interfacial adhesion, are vulnerable to delamination under thermal and electromagnetic stresses. This delamination failure precipitates a catastrophic degradation of the current-carrying capability, compromising the reliability and safe operation of superconducting systems. However, existing studies on this delamination behavior of YBCO CCs have been restricted to room temperature and 77 K, inadequately covering the crucial 20–77 K operating range required for superconducting applications. In this study, we designed a dedicated horizontal delamination test fixture to measure the delamination strength of YBCO CCs across the wide temperature range of 20–293 K. Finite element analysis was employed to obtain the thermal mismatch stress, thereby validating the reliability of the test method. The delamination strength of YBCO CCs exhibits a non-monotonic dependence on temperature. It initially decreases as the temperature drops to 60 K, then increases sharply below this temperature. Notably, the delamination strength was measured to be 37.41 MPa at 20 K, representing the maximum value compared to the data obtained at higher temperatures. These findings indicate that the delamination strength measured at 77 K is applicable to 20–50 K temperature conditions and still maintains a considerable safety margin.