Speaker
Description
REBCO coated conductor (CC) has been applied to high field magnets due to its high critical current density ($Jc$) and high tensile strength. In order to further improve in-field $Jc$, we have developed EuBCO CCs doped BaHfO$_3$ (BHO) as artificial pinning centers (APCs)$^{[1]}$. Since the EuBCO nanocomposite films with the BHO secondary phase is similar to the structure for improving the strength and fracture toughness in bulk ceramics$^{[2]}$, there is a possibility that the strength of the BHO-doped EuBCO CCs is also improved. However, it was difficult to directly measure the strength and fracture toughness of the superconducting layer in the CCs. As a new approach, we introduced the microcantilever beam method$^{[3]}$ to evaluate the micromechanical properties of the superconducting layer. Microcantilever beam specimens (~ $\mu$m) were formed in the superconducting layer by focused ion beam (FIB) processing. Their strengths were measured by bending tests using a nanoindenter. We will report on details of the test method and a comparison of the strength of the CCs.
Acknowledgments
A part of this work is based on results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO).
[1] S. Fujita et al., IEEE TAS., 28, 4 6600604 (2018).
[2] K. Niihara et al., J. Ceram. Soc. Jpn., 99, 974 (1991).
[3] J. Tatami et al., J. Am. Ceram. Soc., 98 3 965–971 (2015).
