High Magnetic Flux Trapping by Melt-Grown YBaCuO Superconductors

Abstract

Trapped magnetic flux density of melt-grown YBaCuO bulk superconductors was evaluated. A single-grained disc-shaped bulk sample with a size of 45 mmφ×15 mm trapped very high magnetic flux density after field cooling. One disc trapped a maximum surface flux density of 0.72 T, while the maximum of double-piled discs was 1.35 T after 100 seconds. A polygrained sample showed a much lower maximum. The pinning potential of this single-grained disc was 0.17 eV, and the overall critical current density estimated from the trapped flux density was about 7×103 A/cm2. Since these values are lower than those of a small-sized sample, weak links are still expected to exist even in the single-grained sample. Domain structure within a grain is a strong candidate for this weak link.

Superconductivity, High‐Temperature

“…A "top-seeding technique" (Sawano et al, 1991) can control the crystal nucleation and growth during melt texturing: It is essential for obtaining large quasi single-grain HTSrs. The technique involves introducing a small single-grain HTSr as a seed to the top of the HTSr precursor, with or without a temperature gradient, before melt texturing.…”

Magnetic Alignment in $\hbox{REBa}_{2}\hbox{Cu}_{3-{\rm x}}\hbox{Co}_{\rm x}\hbox{O}_{\rm y}$ Compounds

“…The formation of a bi-axial or tri-axial grain-oriented microstructure is indispensable for the development of HTSC materials with higher J c . In practice, in the case of RE123 superconductors, epitaxial growth techniques, such as melt-solidification using a seed crystal [3] and thin film growth using a highly oriented substrate [4], have been utilized for the achievement of bi-axial orientation of RE123. Recent improvements in magnetic alignment techniques are remarkable.…”

Analysis of Electromagnetic Phenomena in HTc Superconductors

“…Exceptional electromagnetic phenomena appearing in these materials should be taken into account for this aim. One of them is connected with fabrication of large single grains Y-123 superconducting monoliths, trapping magnetic induction significantly exceeding the values achievable using other permanent magnets [1,2]. This effect allows to treat HTc superconductors not only as resistivity-less perfectly conducting materials but also as very promising permanent magnets.…”