Growth of large bulk Y–Ba–Cu–O with multi-seeding

Abstract

Large bulk Y-Ba-Cu-O superconductors, 62 mm in diameter and 12 mm in thickness, have been fabricated by a cold seeding method in which four seeds are placed on top of the precursor at room temperature prior to melt processing. The advantage of a cold seeding technique is that the desired seeding location can be arranged at room temperature. However, due to the reaction of the seed with the precursor at high temperatures, controlled single-grain growth has been difficult. In the present study, we carefully investigated the influence of the processing parameters such as the maximum heating temperature, the dwelling time at this temperature, the temperature to start slow cooling and the slow cooling rate on the grain growth behavior. Through the optimization of these processing parameters, we have succeeded in growing large bulk Y-Ba-Cu-O with four large grains. The sample with 1 wt% CeO 2 addition showed almost the same field trapping ability as a single-domain sample.

A buffer bridge process for growing multiple YBa2Cu3O7 −ygrains from one top seed

“…Moreover, the seed/compact interface area in the buffer bridge process, which is the route for impurity diffusion, can be minimized by using of a reduced number of seeds. The reduced number of seeds is comparable to large area seeding [12,13] and the multi-seeding technique [14][15][16][17] which uses several seeds. Another advantage is the growth of multiple Y123 grains from one seed, which makes it possible to fabricate several single-grain Y123 superconductors using one top seed.…”

“…As a result of the samarium diffusion into Y123 compacts, the mixed rare-earth 123 and 211 phases formed in the compact regions, which caused the non-uniform T c and J c distribution of the top surface [7,8,11]. For large seeds [12,13] and multiple seeding [14][15][16][17], which were configured for the purposes of reducing processing time, the impurity contamination becomes more serious due to the large seed/compact interface area, which acts as a diffusion path for the impurities. Two research groups developed a new process in order to prevent impurity contamination from seeds [11,18].…”

Improvement of Superconducting Joint Properties for GdBa2Cu3Ox Bulk Superconductors Joined with ErBa2Cu3Ox Superconductor Using Local Melt-Growth Method

“…This is because the crystal growth rate is slow, and microstructural changes, such as segregation and compositional change, tend to occur during crystal growth, which results in the degradation of the superconducting properties. The multi-seeded melt-growth method has been devised as one of the solutions [14][15][16][17][18]. In this method, multiple seed crystals are placed on a large precursor before the melt-growth process begins, and crystals are grown from each seed crystal to achieve larger dimensions.…”

Influence of layered precursor pellets on the growth and properties of Y-Ba-Cu-O bulk superconductors by top-seeded melt-textured growth

“…In recent years, with the continuous improvement of the fabrication processes of melt-textured bulk high-temperature superconductors, large bulk RE-Ba-Cu-O (RE denotes rare Earth elements) has shown great potential in large-scale engineering applications such as permanent magnets [1]; superconducting magnetic bearings and flywheel energy storage systems [2][3][4][5]; and superconducting noncontact conveyors or torque transfers [6,7], due to its unique properties of auto-stable levitation and a stronger ability to trap magnetic fields than iron-based, permanent magnets. In particular, bulk Y-Ba-Cu-O (YBCO) has become an appealing candidate for industrial application material because the preparation method is simple, reliable and low cost.…”