Hot isostatic pressing of bulk magnesium diboride: Mechanical and superconducting properties

Hot isostatic pressing with glass encapsulation (pressure, 200MPa; temperature, 1000C over 200min; cooling under pressure) was used to synthesize bulk MgB 2 with diameters up to 20mm and thicknesses up to 10mm from MgB 2 powder. A sharp superconducting transition was measured at 38.5K. This method can be scaled to larger sample sizes and complex shapes. The data for density, microhardness, fracture toughness and sound speed for bulk magnesium diboride are presented. Ball milling the powder results in a more homogeneous final microstructure with a higher resistivity and with a similar superconducting transition.