Effect of oxygenation on levitation force in seeded melt grown single-domain YBa2Cu3Ox

The homogeneity of levitation force in single domain YBCO bulk

“…7 that there is a peak value in the levitation force curve, and the peak value occurs at the second disk. The same phenomenon is in accordance with Donglu Shi et al's experiments [10]. As the top surface is gradually lapped after oxygenation, the levitation force has been found to increase and peaks at a depth about 1.5 mm [10].…”

“…The same phenomenon is in accordance with Donglu Shi et al's experiments [10]. As the top surface is gradually lapped after oxygenation, the levitation force has been found to increase and peaks at a depth about 1.5 mm [10]. This indicates that the levitation forces are closely related to the superconductor bulk position, but the interpretation about levitation forces decreasing in the bottom is not satisfactory.…”

Electric resistance relaxation and oxygen diffusion in melt-texture grown YBCO bulk post-annealed at high temperature

“…For the same reason, it is possible that there is a larger apparent diffusion coefficient and lower activation energy in the as-grown sample, as implied in figure 2. This may be one of the reasons why large MTG-YBCO bulk can be fully oxygenated in a relatively short period compared with the calculated time from the diffusion coefficient obtained in single crystals [4,5]. Although the oxygen diffusion parameter obtained from the above treatment is quite an approximate one, it clearly shows the important role of grown defects on the electric resistivity relaxation and oxygen diffusion, i.e.…”

“…The mosaic size is from <1 µm up to some tens of micrometres, depending on the amount of Y211 and the growth conditions [23]. Meanwhile, the micro-cracks and voids in MTG-YBCO bulk have also been reported [4,25] and the distance between the microcracks is of the order of 10-20 µm. Obviously those imperfections change the diffusion behaviour, and the value of D estimated above is actually overestimated as an upper limit value for MTG-YBCO with a given microstructure.…”

“…Under normal growing conditions, the MTG-YBCO sample cannot obtain enough oxygen to reach thermodynamic equilibrium at low temperature, particularly for the large size bulk with single domain, which is very important in many practical applications. The oxygen uptake at low temperatures around 400 • C is also necessary for high performance including the macroscopic magnetic levitation force [4,5]. Moreover, compared with usual sintered ceramics and single crystals, MTG-YBCO is obtained through a peritectic reaction between the solid Y 2 BaCuO Z (Y211) (where Z = 5 for stoichiometery) and Ba-Cu liquid.…”