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We report a complete procedure to achieve multilayer YBa2Cu3O7−δ (YBCO) thick films by electrophoretic deposition on silver tubes using a suspension of YBCO powder in butanol. With the aim to optimize the magnetic shielding performances of the coatings, we have carried out an extensive investigation of the influence of the deposition parameters, the multilayer deposition sequence and the intermediate/final heat treatments on the coating microstructure. Using the optimized conditions, a 24-layer YBCO coating has been successfully prepared on an 80 mm long Ag tube: the melt growth processed multilayered YBCO thick film thus obtained can shield an applied magnetic field of 1.9 mT at 77 K, the highest value per thickness unit reported so far in the literature for these materials.

Bulk YBa2Cu3O7 − δ (YBCO)/Ag composites with a homogeneous distribution of fine and spherical particles of metallic silver and Y2BaCuO5 (Y-211) have been fabricated using a preform optimized infiltration growth process (POIGP). The effect of two different methods of introducing silver, one directly into the Y-211 preform and the other into the liquid phase source placed above the Y-211 preform, on the microstructures and current densities is investigated. Our results show that the latter method is far superior to the former. The samples obtained by introducing silver through liquid phases are nearly free from defects like voids, pores, macro-cracks and platelet gaps. Current densities in excess of 103 A cm − 2 up to fields of 2.7 T have been recorded in these samples at 77 K. The problems reported in literature with respect to inhomogeneity in the distribution of both Y-211 and Ag particles in the Y-123 matrix and the associated spatial non-uniformity in the current density are successfully resolved in the present work.

We report record high current densities of 230 kA cm − 2 at zero field, and in excess of 10 kA cm − 2 up to 7 T at 77 K, in YBa2Cu3O7 − δ (Y-123) superconductors fabricated by a modified infiltration growth (IG) process. This was accomplished by optimizing the Y2BaCuO5 (Y-211) preform, into which liquid phases were infiltrated, through a combination of high pressure compaction and limiting the sintering temperature. The optimized sample yielded a Y-123 superconductor with a uniform distribution of fine-grained Y-211. Strong and almost invariant flux pinning observed to high fields up to 7 T, suggest a temperature independent flux pinning mechanism originating from defects in the size range 15–50 nm. Since the present sample has no added grain refiners, nano-sized dopants or mixed rare earths leading to low Tc solid solutions, a unique opportunity presents itself to investigate the cause of the enhanced flux pinning to high fields. We have therefore investigated our samples by transmission electron microscopy, and the studies revealed the presence of domains in the sample with nano-sized defects starting from the domain boundaries, as a possible source of enhanced flux pinning.