Relationship between microstructure and superconducting properties of the MgB₂ bulk fabricated from the gas–solid method

Abstract The gas–solid method, discovered in recent years, has been shown to have the potential to fabricate dense MgB 2 bulks. In this study, we aimed to investigate the dominant regulation mechanism underlying the superconducting properties and microstructures of MgB 2 bulk obtained from the gas–solid method. To this end, we utilized nano computed tomography (nano CT) and transmission electronic microscopy to examine the structure of the MgB 2 bulk at the micrometer and nanometer scales, respectively. Nano-CT results revealed that the application of a mold during the gas–solid process can significantly reduce the amount of holes present in the sample. Furthermore, the reticular hole structure can be almost completely eliminated through this modification. Such a change can account for the remarkable increase in superconducting connectivity ( A f value) observed in the sample with a mold. Additionally, we found that different B powders can lead to vastly different MgO impurity particle sizes and distributions at the nanometer scale. This finding can explain the differing J c (B) values and pinning forces observed in the corresponding samples. Overall, our correlation analysis between the structure and superconducting properties provides valuable insights into the possible regulation mechanism of MgB 2 bulk obtained from the gas–solid method. These findings may assist researchers in further improving the performance of MgB 2 bulks.