Manufacture of Bi-cuprate thin films on MgO single crystal substrates by chemical solution deposition

Bi2Sr2CaCu2O8 thin films have been deposited on MgO single crystal substrates by spin-coating a solution based on 2-ethylhexanoate precursors dissolved in xylene. Pyrolysis takes place between 200 degrees C and 450 degrees C and is accompanied by the release of 2-ethylhexanoic acid, CO2 and H2O vapour. Highly c-axis oriented Bi2Sr2CaCu2O8 as well as Er-or Ho-doped Bi2Sr2(Ca, Ln)Cu2O8 (Ln = Er, Ho) films were obtained after heat treatment at 840 degrees C in air

Novel approach for manufacture of single-grain EuBCO/Ag bulk superconductors via modified single-direction melt growth

AbstractDespite the success of top‐seeded melt growth (TSMG) and TSIG, some key aspects of their manufacture need to be addressed including the presence of microstructural defects, inhomogeneities in trapped field and the difficulty of growing large‐diameter bulk monoliths. Recently, a promising new method single‐direction melt growth (SDMG) appears to address the majority of the shortcomings of TSMG and TSIG. Single‐grain EuBCO/Ag bulk with the highest peritectic temperature to date was grown by modified SDMG. This remarkable achievement was made possible by lowering the peritectic temperature of the precursor composition by the addition of silver and by using single‐grain EuBCO fabricated by TSMG as a seed. The EuBCO/Ag bulk grown by SDMG has demonstrated significant improvements in comparison to a reference TSMG sample. A reduction of approximately 30% in defect area (associated primarily with porosity), as well as a significantly enhanced homogeneity of trapped field and critical temperature, was observed. Furthermore, the critical current density curves exhibit a considerable improvement, particularly in the 2–5 T field range. The SDMG technique has considerable potential for scale‐up for the fabrication of large‐diameter bulk single grains, with only growth along the c‐axis involved during the thermal process.</jats:p

Enhanced mechanical properties of single-domain YBCO bulk superconductors processed with artificial holes

Single domain YBCO bulk superconductors were prepared using a conventional top-seeded melt growth (TSMG) technique. Artificial holes were introduced to the green sample prior to thermal processing using a bespoke “spiked” mould. Me- chanical properties such as elastic modulus, Vickers hardness, compressive strength and tensile strength were measured and compared to the properties of a standard bulk. The presence of the holes the bulk microstructure was observed to limit porosity and lower the concentration of macro-cracks in the bulk microstruc- ture, resulting in significantly enhanced mechanical properties of the bulk single grains. The elastic modulus of the perforated bulks was observed to exhibit an increase of more than 45% compared to the standard samples. Compressive and tensile strengths were also improved significantly in the samples containing artificial holes. Observed differences in Vickers hardness, on the other hand, were negligible. This could be due by the fact that the hard- ness is measured on a small surface area of the single grain sample, where the effect of lower porosity and lower concentration of macro-cracks is less relevant. The introduction of artificial holes to the bulk, single grain microstructure appears to be a very prom- ising technology for the production of melt-textured bulk super- conductors with enhanced mechanical properties

Cost-effective isothermal top-seeded melt-growth of single-domain YBCO superconducting ceramics

In this work, a series of melt processed Y–Ba–Cu–O (YBCO) single-grains have been fabricated by the top-seeded melt growth (TSMG) technique. The melt processing is accepted widely as an effective way to grow bulk, single grain YBCO superconductors; however, this process is extremely complex and every step can affect the final properties of prepared bulk. Therefore, the impact of precursor powder preparation and growth conditions was studied for the first time. Cost-effective in-house made powder and commercially available precursor powders were employed and samples were grown employing top seeded melt growth, following the isothermal and the under-cooling growth techniques. The bulk microstructure including Y 2 BaCuO 5 (Y-211) particle size and distribution, superconducting properties (T c , J c ) and field trapping potential were investigated. The cost-effective high performance batch processing methodology was optimized. The fabricated YBCO bulks (diameter of 28 mm) exhibited average trapped field of 0.85 T at 77 K. Furthermore, other possibilities to achieve advancement in processing (RE)BCO bulks, are proposed

Cost-effective isothermal top-seeded melt-growth of single-domain YBCO superconducting ceramics

Abstract In this work, a series of melt processed YBaCuO (YBCO) single-grains have been fabricated by the top-seeded melt growth (TSMG) technique. The melt processing is accepted widely as an effective way to grow bulk, single grain YBCO superconductors; however, this process is extremely complex and every step can affect the final properties of prepared bulk. Therefore, the impact of precursor powder preparation and growth conditions was studied for the first time. Cost-effective in-house made powder and commercially available precursor powders were employed and samples were grown employing top seeded melt growth, following the isothermal and the under-cooling growth techniques. The bulk microstructure including Y2BaCuO5 (Y-211) particle size and distribution, superconducting properties (Tc, Jc) and field trapping potential were investigated. The cost-effective high performance batch processing methodology was optimized. The fabricated YBCO bulks (diameter of 28 mm) exhibited average trapped field of 0.85 T at 77 K. Furthermore, other possibilities to achieve advancement in processing (RE)BCO bulks, are proposed.Czech Ministry of Industry and Trade, project TIP (FR-TI4/184)

Dataset for 'Improved trapped field performance of single grain Y-Ba-Cu-O bulk superconductors containing artificial holes'

Dataset accompanying the paper entitled ‘Improved trapped field performance of single grain Y-Ba-Cu-O bulk superconductors containing artificial holes’, which measured the tensile strength of standard and thin-wall (i.e., with artificial holes) YBCO samples then subsequently confirmed the effect of the strength improvement on the trapped field capability of the different sample types. The dataset contains results obtained using the following techniques: (i) the Brazilian test to measure tensile strength of cylindrical samples, (ii) optical microscopy to measure sample porosity and (iii) a 12-tesla high-field magnet to magnetise and break the samples when they were superconducting. Explanations of figures containing experimental results: Fig. 3b shows the ramp rates used to magnetize the samples. The rates were fixed for each field range. Fig. 4 shows the strength of various sample types (i.e. standard, thin-wall) measured using the Brazilian test. Fig. 5a shows the optical images taken at half height across each sample, and Fig. 5b shows the porosity analysis on these images using ImageJ software. Fig. 6a and 6b show the performance of the two sample types, i.e. field trapped by the sample as a function of the applied field, showing where the sample failed. The samples were magnetized using the 12-tesla magnet. Fig. 7b shows the 2D field profile measured on the surface of the thin-wall sample using an array of hall sensors. Fig. 8 shows the field measured along the diameter of the thin-wall sample when magnetised using 11 T at 30 K

Improved trapped field performance of single grain Y-Ba-Cu-O bulk superconductors containing artificial holes

The intrinsic mechanical properties of single-grain RE-Ba-Cu-O bulk high temperature superconductors can be improved by employing a thin-wall geometry. This is where the samples are melt-processed with a pre-defined network of artificial holes to decrease the effective wall thickness. In this study, the tensile strengths of thin-wall YBCO discs were determined using the Brazilian test at room temperature. Compared with conventional single grain YBCO discs, the thin-wall YBCO discs displayed an average tensile strength that is 93 % higher when the holes were filled with Stycast epoxy resin. This implies a thin-wall sample should, in theory, be able to sustain a trapped field that is 39 % higher without exceeding the mechanical limit of the sample. High-field magnetisation experiments were performed by applying magnetisation fields of up to 11.5 T, specifically to break the samples in order to verify the effect of increased mechanical strength (and improved cooling) on the ability of bulk (RE)BCO to trap field successfully. The standard YBCO sample failed when it was magnetised with a field of 10 T at 35 K, suffering permanent damage. As a result, the standard sample could only trap a maximum surface field of 7.6 T without failure. On the other hand, the thin-wall YBCO sample survived all magnetisation cycles, including a maximum magnetisation field of 11.5 T at 35 K, demonstrating a greater intrinsic ability to withstand significantly higher electromagnetic stresses. By subsequently field-cooling the thin-wall sample with 11 T at 30 K, a surface field of 8.8 T was trapped successfully without requiring any external ring reinforcement

Preparation and characterization of Bi₂Sr₂CaCu₂O_8+δ thin films on MgO single crystal substrates by chemical solution deposition

Bi2Sr2CaCu2O8 thin films have been deposited on MgO single crystal substrates by spin-coating a solution based on 2-ethylhexanoate precursors. Pyrolysis takes place between 200 degrees C and 450 degrees C and is accompanied by the release of 2-ethylhexanoic acid, CO2 and H2O vapour. Highly c-axis oriented Bi2Sr2CaCu2O8 films were obtained after heat treatment at 840 degrees C in air. The highest T-c of 81 K was measured in a 10-layer film. Subsequent post-annealing in Ar and pure O-2 did not improve the superconducting properties of the films and resulted in the appearance of Bi2CaCuO5 or Bi-2(Sr, Ca)(2)CuO6 impurities. (C) 2013 Elsevier B.V. All rights reserved