Structure of MgB2 ceramics obtained by spark plasma sintering and hot pressing methods

Spark plasma sintering (SPS) and traditional hot-pressing (HP) sintering were used to produce bulk MgB 2 ceramics from commercial powder. The structure of ceramics was studied using SEM, TEM, and X-ray diffraction analysis. The density of the SPS ceramics obtained at 1100°C was 2.35 g/cm 3 , which corresponds to 91% of the theoretical density of MgB 2 but with increasing temperature the MgB 2 phase decomposes to form magnesium tetraboride. It was shown that in the SPS method, MgB 2 decomposition begins already at a temperature of 700°C, and increasing the sintering temperature to 1100°C leads to a significant increase in the volume fraction of the MgB 4 phase from 8% to 44%. Partial sintering by the HP method resulted in a porous structure representing a continuous ceramic framework of the superconducting phase with a critical current density J C = 1.15 × 10 6 A/cm 2 (at a temperature of 30 K in zero field) . This shows that the formation of MgB 2 with high superconducting properties is possible at moderate temperatures and pressures.