MgB2 reactive sintering from the elements

High density MgB₂ compacts have been obtained without the need of high pressure apparatus. The key features of the sintering technique are based on the Mg liquid infiltration on powdered B preforms. Critical parameters, other than the thermal cycles, are the B powder granularity, the density of the preform and the type of the container. Centimeter-sized samples of different shapes have been obtained and the best transport critical current density, measured so far, is about 3 kA/cm² at T = 4.2 K and B = 9 Tesla for a sample having an overall density of 2.40 g/cm³. Possible applications of the MgB₂ compacts are foreseeable in bulk superconducting magnets, magnetic screens and superconducting bars of variable resistance.