Diffusion bonding of the textured Ni tapes for the substrate of YBCO coated conductors

Observation of magnetic fields due to persistent currents in a ring made of a Y1Ba2Cu3O7-δcoated conductor

“…The bonding area was about 10 mm×0.5 mm. Other conditions were the same as in [4]. In order to polish the surface, a Teflon bar, the diameter of which was exactly the same as that of the ring but reduced slightly by cooling in liquid nitrogen for easy insertion, was placed inside the ring.…”

“…The measured critical currents were much smaller than those of the coated conductors [1,2], which implies that the superconducting connection in the bonding region of the ring is not good enough. As described in [4] the range of the mechanical pressure for good bonding is narrow: low pressure causes insufficient bonding and high pressure causes deterioration of textures. The ring is an inconvenient structure for applying uniform pressure, which seems to be the main reason for the weakly linked bonding.…”

“…For example, a ring made of a superconducting tape is a simple structure, where the two ends of the tape are connected so that the superconducting current flows circularly along the closed path. We have already reported a method for bonding two textured Ni tapes [4]. The process of atomic diffusion bonding includes several steps: polishing and shaping the ends of two tapes, overlapping and heating them for atomic diffusion bonding while they are mechanically pressed, and final polishing [4].…”

“…We have already reported a method for bonding two textured Ni tapes [4]. The process of atomic diffusion bonding includes several steps: polishing and shaping the ends of two tapes, overlapping and heating them for atomic diffusion bonding while they are mechanically pressed, and final polishing [4]. We deposited a YBCO film on the bonded tapes using buffer layers, CeO 2 /YSZ/CeO 2 , and achieved ∼10 5 A cm −2 of critical current.…”