Melt-processed Gd–Ba–Cu–O superconductor with trapped field of 3 T at 77 K

Abstract

We fabricated a single-domain Gd–Ba–Cu–O bulk superconductor 65 mm in diameter and studied the microstructure, superconducting and field-trapping properties. Melt-processing was performed under a controlled oxygen partial pressure of 1.0% using a precursor containing Gd123 and Gd211 powders in a molar ratio of 2:1, with 0.5 wt% of Pt and 20 wt% of Ag2O added. The distribution of Ag and Gd211 particles was almost homogeneous. The addition of Ag was very effective in reducing the amount of cracking in the sample. The maximum trapped magnetic field recorded was 3.05 T at 77 K. We also measured the trapped field between two Gd–Ba–Cu–O bulk samples in order to minimize the demagnetizing effect and found that the trapped field reached 4.3 T at 77 K.

Study of buoyancy driven heat transport in silicone oils and in liquid nitrogen in view of cooling applications

“…The governing equations (1)(2)(3)(4)(5) are solved by a finite-volume method using a general purpose computational fluid dynamics (CFD) software [23]. The pressure-velocity coupling between the incompressible Navier-Stokes and the continuity equations are solved using the SIMPLE algorithm [24].…”

“…High-temperature superconducting materials in the form of single grains of a few cm 3 are capable of trapping magnetic flux densities exceeding those of conventional permanent magnets. Magnetic flux densities in excess of 17 T were trapped in bulk superconductors at temperatures below 30 K [1,2], and densities up to 3 T were trapped at 77 K [3].…”

“…Magnetic flux densities in excess of 17 T were trapped in bulk superconductors at temperatures below 30 K [1,2], and densities up to 3 T were trapped at 77 K [3]. Bulk superconductors are thus very promising materials to be used in electrical systems such as motors, generators, magnetic bearings, and magnetic resonance devices [1,2].…”

Improvement of Critical Current Density and Flux Trapping in Bulk High-Tc Superconductors

“…It was difficult to oxygenate the bulk sample with a big diameter and in this case the oxygen should diffuse into the core of the bulk. Generally, the big samples are annealed under oxygen at 400-450 °C between 150 to 600 hours [42,46,53,54]. These annealing dwell times are so long in order to allow for oxygen diffusion until the core of the monolith bulk materials.…”

“…11 where 25 hours is sufficient to obtain the full oxygenated sample; in the other word, maximum weight gain is quickly achieved. In addition, thin-wall geometry was introduced to reduce the diffusion paths and to enable a progressive oxygenation strategy [54]. As a consequence, cracks are drastically reduced.…”