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No abstract

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. Mechanical 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 microstructure, 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 hardness 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 promising technology for the production of melt-textured bulk superconductors with enhanced mechanical properties.