Dense MgB₂ Ceramics by Ultrahigh Pressure Field-Assisted Sintering

Magnesium diboride (MgB₂) ceramics, due to their impressive transition temperature of 39 K for superconductivity, have been widely investigated. The possibility to obtain highly dense MgB₂ ceramics with fine microstructure and grain boundaries acting as pinning sites by novel high-pressure-assisted spark plasma sintering (HP-SPS) is reported in this article. HP-SPS was employed to reach 100% density in MgB₂ ceramics, and high pressure was utilized in the consolidation of MgB₂. An increase in pressure helped in stabilizing the MgB₂ phase above thermal decomposition, thus avoiding the formation of non-superconducting phases such as MgO and MgB₄. Pressure allowed strengthening of the covalent bond (condensation effect) to increase the thermal stability of MgB₂. HP-SPS yielded high mechanical hardness in MgB₂ (1488 HV). For better electrical connectivity, which leads to large magnetic moments in high density samples were obtained with the beneficial effect of high applied pressure (1.7–5 GPa) at high temperature (>1000 °C). The combination of the SPS process and high pressure ensured retention of the homogeneous fine microstructure required to obtain high current density and high hardness. View Full-Text