Practical applications, such as MRI, generators and motors, require high critical current (Ic) in a magnetic field. For this reason, increasing the film thickness d and enhancing flux pinning are extremely important. So far, we have succeeded in obtaining high in-field Ic by controlling the crystal growth rate and introducing BaZrO3 nanoparticles (BZO NPs) into trifluoroacetate metal organic deposition (TFA-MOD) grown (Y0.77Gd0.23)Ba2Cu3Oy ((Y,Gd)BCO) coated conductors (CCs) [1]. Recently, we have reported more improvement of the in-field critical current density (Jc) by introducing BaHfO3 (BHO) NPs instead of BZO NPs [2-4]. However, the influence of the film thickness dependence of the in-field Jc and of the microstructure of (Y,Gd)BCO +BHO CCs is not clear.
In this work, to investigate the film thickness dependence of Jc at various temperatures (85, 77 and 65 K), we prepared standard (Y,Gd)BCO and 12 vol.% BHO-doped (Y,Gd)BCO CCs with various thicknesses. For all thicknesses, films and temperatures, (Y,Gd)BCO+BHO CCs show a higher Jc compared to that of YGdBCO CCs. Despite the fact that for thinner films Jc decays rapidly with increasing thickness (), for thicker films the Jc value is almost constant. This thickness dependence of Jc may be caused by the change of depensation of pinning (2-dimensional pinning in thinner films and 3-dimensional pinning in thicker films). Detailed experimental results for nanocomposite (Y,Gd)BCO CCs will be presented.
Acknowledgements:
This work was supported by JST-FOREST (Grant Number JPMJFR202G). A part of this work at Seikei University was supported by JSPS KAKENHI (20H02184).
1. M. Miura, Springer 2015 (ISBN:978-3-319-14477-1), chapter 1, pp.3-26.
2. M. Miura et. al., NPG Asia Materials 9 (2017) e447.
3. S.C. Jones, M. Miura et. al., APL Materials 9 (2021) 091105.
4. M. Miura et. al., NPG Asia Materials (accepted on Sep. 6th, 2022)