A novel preform compaction method for fabricating high-performance Y–Ba–Cu–O single-grain bulk superconductor

A novel preform compaction method based on one new type of divisible mould was employed for fabricating single-grain YBCO bulk superconductor, which can complete the preform demoulding process through opening of the mould, rather than pushing the preform out in the regular mould. Thus it has natural superiority on eliminating macro-cracks, which has been proved by the sample surface morphology and the trapped field characterization. In addition, the divisible mould pressed sample exhibits higher levitation force and trapped field properties than the regular mould pressed samples, verifying the potentials of the divisible mould on improving the bulk performance. The optical micrograph results prove the superiority of the divisible mould on eliminating tiny cracks on sample surface. The processing facility and sample reliability brought by the divisible mould should also be emphasized, because the crushing and re-pressing of preform when it presents visible cracks can be omitted and the failed samples with surface cracks will no longer appear. Consequently, the experimental efficiency and stability are both enhanced.

Analysis of Electromagnetic Properties of Bulk Superconductors

In the present study, a YBa2Cu3O7−y bulk superconductor added with 5~10 wt% Ag was fabricated employing Sm123 as a seed to produce a superconductive single crystal. Metallic silver was added to the single crystal of YBa2Cu3O7−y to remove defects such as cracks and pores. Electromagnetic properties of the bulk superconductor at 77 K were analyzed based on relationships of magnetic levitation, trapped magnetic force, and critical current density. The critical current density of the superconductor at 77 K and 0 T was 3.53 × 104 A/cm2. Discontinuous points in the distribution of magnetic field lines were not observed, implying that these two specimens grew well as a single crystal without specific weak links. For the growth of a superconductive nano crystal employing slow cooling at temperature of formation of 123 phase, superconductive nano crystals were aligned in a-b direction, the direction of peak current flow. The peak value of the trapped magnetic force of the YBa2Cu3O7−y superconductor specimen was 3.23 kG. Using the FC method, peak forces of attraction and repulsion were 21.696 N and 70.168 N, respectively.

Influence of Artificially Macroscopical Drilling on the Crystal Growth Orientation of Single Domain SmBCO Bulk Superconductor

A large drilled single domain SmBa2Cu3O7−δ (SmBCO) bulk superconductor with a diameter of 32 mm and different hole sizes was successfully fabricated using the modified top-seeded infiltration and growth (TSIG) process. The morphology, superconducting properties, and grain boundary orientation growth of the drilled SmBCO samples were investigated. It was found that not only are the properties of the drilled sample equivalent to those of normal SmBCO bulk superconductors, but also the NdBCO seed crystal can be well controlled because of the increase in the specific surface area in the solid phase pellet. In addition, the growth orientation along the tangent direction of the holes was first noticed in the drilled single domain SmBCO bulk superconductor. This conclusion is highly important for the accurate control of the growth temperature of high temperature bulk superconductors.