Employment of NdBCO/YBCO/MgO film seed in the infiltration growth technique for fabricating single-grain YBCO bulk superconductors

Abstract

The quality of the seed is a key factor for growing well c-axis oriented RE–Ba–Cu–O (REBCO) single-grain superconductors. In this study, the commercial NdBCO/YBCO/MgO film (300 nm NdBCO with 20 nm YBCO buffer layer on MgO substrate) is employed as seed in the infiltration growth (IG) method for growing YBCO single grains, including the conventional 211-IG and the novel 011-IG techniques. And an embedded seed mode was used for preventing the movement of the thin film during heat treatment process in the 011-IG technique. The results indicate that, YBCO single grains have been successfully grown via the seeding of NdBCO/YBCO/MgO film in the two IG processes, which proves the feasibility of the film seed in the IG method. Four strictly perpendicular growth sector boundaries on the top surface of the samples and clear (0 0 l) diffraction peaks in the X-ray diffraction (XRD) results both indicate the high c-axis orientation and well growth quality of the samples, which proves the excellent performance of the NdBCO/YBCO/MgO film seed in the IG method. Superconducting property measurement showed that, the 011-IG YBCO sample exhibited enhanced levitation force and Jc properties than the 211-IG sample.