Complex microstructural analysis of YBCO single-grain bulks with artificial holes: Effect on superconducting properties

Abstract

This work presents an investigation of the microstructural and superconducting properties of standard single-grain bulk superconductor Y–Ba–Cu–O (YBCO) and samples fabricated with artificial holes. It was shown that the presence of artificial holes reduces the absolute porosity of the sample. The presence of artificial holes did not improve the homogeneity of oxygen distribution in the samples after oxygenation. The distribution of Y211 particles in the samples has a negligible effect on the macroscopic superconducting properties. In the process of crystal growth, the ellipticity of the introduced holes and their displacement in the direction of crystal growth in the growth sectors arise. Macroscopic superconducting properties, such as levitation force and trapped magnetic field at 77 K, were supplemented by magnetization measurements of superconducting transition temperature and critical current density. The levitation force and the trapped magnetic field were higher for the sample with holes. For the measured trapped magnetic field, the decrease of the porosity in the a-growth sectors, which have a higher volume fraction of Y2BaCuO5 (Y211) particles, and consequently stronger pinning, is significant.