Bulk samples of MgB 2 have been formed by hot isostatic pressing (HIPping) of commercial powder at 100MPa and 950°C. The resulting material is 100% dense with a sharp superconducting transition at 37.5K. Microstructural studies have indicated the presence of small amounts of second phases within the material, namely MgO and B rich compositions, probably MgB 4 . Magnetisation measurements performed at 20K have revealed values of J c =1.3 x 10 6 A/cm 2 at zero field, and 9.3 x 10 5 A/cm 2 at 1T. Magneto optical (MO) studies have shown direct evidence for the superconducting homogeneity and strong intergranular current flow in the material. IntroductionSince the discovery of superconductivity in MgB 2 at 39K [1] numerous attempts have been made to produce high density compacts. This has proved relatively difficult, mainly due to the high volatility of Mg at elevated temperatures. Despite this, MgB 2 compacts have been successfully prepared by various methods. These have included uniaxial pressing of mixtures of Mg and B [2][3][4][5], and sintering at high pressures, ≥ 3GPa, of MgB 2 powder [6][7][8]. The latter method has been the most successful in producing fully dense samples. HIPping has also been used to produce compacts. Nagamatsu et al [1] in their original studies pressed Mg and B powder at 700°C and 196MPa. Commercial MgB 2 powder has also been HIPped at 1000°C and 200MPa [9,10] to produce high density compacts. This paper reports the successful fabrication of MgB 2 compacts with high density and good superconducting properties by a HIPping process at 100Mpa and 950°C.

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