2021/01/06 by Yavuz Oz, Jianyi Jiang, Maxime Matras +7
Engineering · Materials Science · Physics and Astronomy · #Anisotropy #Condensed matter physics #Coupling (piping) #Critical current #Cuprate #Grain boundary #Iron-based superconductors research #Josephson effect #Materials science #Metallurgy #Microstructure #Misorientation #Optics #Physics #Physics of Superconductivity and Magnetism #Superconducting Materials and Applications #Superconductivity #Supercurrent #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevmaterials.5.074803
published as Phys. Rev. Materials 5, 074803 (2021) · 10 pages, 4 figures
arxiv created 2021/01/06 · openalex publication_date 2021/07/27 · arxiv updated 2021/08/04 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
Bi2Sr2Ca1Cu2Ox (Bi-2212) is the only high-temperature superconductor (HTS) available as a round wire with high critical current density Jc, which makes it a very compelling candidate for ultrahigh-field magnet applications. By contrast, other copper oxide HTS conductors like RBa2Cu3O_7\ensuremath-\ensuremathδ (where R stands for rare earth) and (Bi,Pb)2Sr2Ca2Cu3Ox (Bi-2223) must be made in tape form to minimize the density of current blocking high-angle grain boundaries. Understanding the mechanism enabling high Jc in round wire Bi-2212 is important intellectually because it breaks the paradigm that forces HTS conductors into tape geometries that reproduce their strong crystalline anisotropy. The biaxial growth texture of Bi-2212 developed during a partial melt heat treatment should favor high Jc, even though its \ensuremath∼15^\ensuremath∘ full width at half maximum (FWHM) grain-to-grain misorientation is well beyond the commonly accepted strong-coupling range of \ensuremath≤5^\ensuremath∘ misorientation. Its ability to be strongly overdoped should be valuable too since underdoped cuprate grain boundaries are widely believed to be weakly linked. Accordingly, we here study property changes after oxygen underdoping the optimized, overdoped wire. While Jc and vortex pinning diminish significantly in underdoped wires, we were not able to develop the prominent weak-link signature [a hysteretic Jc(H) characteristic] evident in even the very best Bi-2223 tapes with an \ensuremath∼15^\ensuremath∘ FWHM uniaxial texture. We attribute the high Jc and lack of weak-link signature in our Bi-2212 round wires to the high-aspect ratio, large-grain, basal-plane-faced grain morphology produced by partial-melt processing of Bi-2212. These features enable c-axis brick wall current flow when ab-plane transport is blocked. We conclude that the presently optimized biaxial texture of Bi-2212 intrinsically constitutes a strongly coupled current path, regardless of its oxygen doping state.