Speaker
Description
The TFA-MOD method is a powerful way to fabricate $\it{RE}$Ba$_2$Cu$_3$O$_{7-\delta}$ coated conductors ($\it{RE}$BCO-CCs) with high critical current properties with a low fabrication cost. In this study, we focused on the case of BaHfO$_3$ nanoparticles (BHO-NPs, which have a diameter of < 10 nm) in $\it{RE}$BCO-CCs fabricated by the TFA-MOD method with an ultra-thin-once-coating (UTOC) process [1] and carried out critical current density ($J_\rm{c}$) measurements under wide temperature (4.2 K < $T$ < $T_\rm{c}$) and magnetic field ($B$ < 24 T) conditions with various magnetic-field orientations including the longitudinal-magnetic-field (LMF, $B\parallel J$) configuration and the transverse-magnetic-field (TMF, $B\perp J$) configurations.
In the TMF configurations, $\it{RE}$BCO with BHO-NPs possessed larger $J_{\rm c}(\theta)$ ($\theta$: angle between $B\perp J,\parallel c$ and $B\perp J,\parallel ab$) compared with those in $\it{RE}$BCO without BHO-NPs under most of $T$ and $B$ conditions, indicating that introduction of BHO-NPs is useful way to improve $J_\rm{c}$. As a characteristic behavior, $\it{RE}$BCO with BHO-NPs showed a broad depression of $J_\rm{c}(\theta)$ around $B\parallel ab$ at higher $T$ and lower $B$. We calculated the elementary pinning force based on the model beyond the widely-used model and succeeded in reproducing the depression naturally.
As for the LMF configuration, $\it{RE}$BCO with BHO-NPs showed larger $J_{\rm c}(B\parallel J)$ than those in $\it{RE}$BCO without BHO-NP, suggesting that the flux pinning by BHO-NPs is effective to enhance $J_\rm{c}$ in the LMF configuration as well as the TMF configurations.
At the conference, we would like to report the more-detailed data described above and to discuss about them.
This work was supported by a matching foundation between AIST and Tohoku Univ., by a research grant from the Japan Power Academy (Specially Promoted research), and by JSPS KAKENHI (18K13783 and 18H05248).
[1] T. Izumi $\it{et\ al}$., IEEE Trans. Appl. Supercond., $\bf{27}$ (2017) 6601604., K. Nakaoka $\it{et\ al}$., Supercond. Sci. Technol., $\bf{30}$ (2017) 055008., M. Miura $\it{et\ al}$., NPG Asia Materials, $\bf{9}$ (2017) e447.
[2] T. Okada $\it{et\ al}$., IEEE Trans. Appl. Supercond., $\it{in\ press}$.
