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

Hot isostatic pressing with glass encapsulation (pressure, 200 MPa; tempera ture, 1000 degreesC over 200 min; cooling under pressure) was used to synth esize bulk MgB2 with diameters up to 20 mm and thicknesses up to 10 mm from MgB2 powder. A sharp superconducting transition was measured at 38.5 K. Th is method can be scaled to larger sample sizes and complex shapes. The data for density, microhardness, fracture toughness and sound speed for bulk ma gnesium diboride are presented. Ball milling the powder results in a more h omogeneous final microstructure with a higher resistivity and with a simila r superconducting transition.