Imperfection of microstructural control in MgB₂ superconducting tapes fabricated using an in-situ powder-in-tube process: toward practical applications

MgB₂ is a promising superconductor for future applications to superconduct wires and tapes used at the liquid hydrogen temperature (20 K). Because the maximal superconducting current (critical current) in MgB₂ depends on its microstructure, an “in-situ” process to fabricate MgB₂ based on a reaction between Mg and B is effective in controlling the microstructure. However, the critical current in the fabricated MgB₂ wires and tapes is not sufficiently high for practical use. This may be attributed to the imperfectness of the microstructural control in MgB₂ wires and tapes. In this paper, we will discuss the microstructural features of MgB₂ tapes fabricated using a typical in-situ powder-in-tube process. By observing the early stage of microstructural evolution in detail, we can gain insights into the next strategy for improving the microstructure of MgB₂ tapes with respect to their applications.