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A bulk YBa 2 Cu 3 O 7− δ (YBCO)/Ag superconducting composite with a homogenous distribution of fine and spherical particles of metallic Ag and Y 2 BaCuO 5 (Y-211) has been fabricated by employing Directionally Solidified Preform Optimized Infiltration Growth Process (DS-POIGP). The effect of adding Ag into the liquid phase source (YBa 2 Cu 3 O 7− δ ) placed above the Y-211 preform on the microstructures and current densities is investigated. The addition of Ag led to a significant refinement of Y-211 particle size and, hence, enabled the enhancement of current densities at low fields.

The effect of compaction pressure applied to the Y 2 BaCuO 5 (Y-211) preform during its fabrication, on the final microstructures and current densities ( J c ) is investigated. The necessity for optimizing the sintering conditions in order to provide mechanical stability to the preform prior to the infiltration of liquid phases is demonstrated. The sample fabricated under optimized conditions showed J c values better than 10 3 A cm −2 up to applied magnetic fields of 6.5 Tesla at 77 K. The microstructural factors influencing the field dependence of J c ‘ J c ( H )’ at low and high fields are investigated. Extensive nano-twinning with large number of crossing twins observed in the optimized sample and the associated high defect densities are correlated to be the source of flux pinning to high fields. The fact that YBa 2 Cu 3 O 7− δ (YBCO, Y-123) superconductor obtained employing the present Preform Optimized Infiltration and Growth Process (POIGP) yields a homogenous and dense distribution of fine Y-211 particles, that creates suitable twin/defect densities to provide flux pinning at high fields, is of technical importance.

The importance of optimizing the fabrication of the Y 2 BaCuO 5 (Y-211) preform in achieving high current densities to high magnetic fields has recently been established. We report the effect of the choice of infiltration temperature 1040 °C (sample A) and 1100 °C (sample B) on the microstructure, magnetic properties and mechanical strength. Both the samples showed [1 0 3] texture after slow cooling through peritectic temperature. Infiltration at higher temperature is found to yield highly dense composites with minimal macrodefects and higher hardness of 18.73 GPa in sample B. Both the samples show uniform distribution of Y-211and comparable zero-field critical current density. High current densities are retained to a higher field of 7 T in sample B, unlike 2 T in sample A. The occurrence of [1 0 3] texture promoting higher hardness, simultaneous with retention of considerably high current density to high fields in sample B has definite advantages for trapped field applications.

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.