Synthesis of MgB(2) at Low Temperature and Autogenous Pressure

High quality, micron-sized interpenetrating grains of MgB(2), with high density, are produced at low temperatures (~420 °C < T < ~500 °C) under autogenous pressure by pre-mixing Mg powder and NaBH(4) and heating in an Inconel 601 alloy reactor for 5–15 h. Optimum production of MgB(2), with yields greater than 75%, occurs for autogenous pressure in the range 1.0 MPa to 2.0 MPa, with the reactor at ~500 °C. Autogenous pressure is induced by the decomposition of NaBH(4) in the presence of Mg and/or other Mg-based compounds. The morphology, transition temperature and magnetic properties of MgB(2) are dependent on the heating regime. Significant improvement in physical properties accrues when the reactor temperature is held at 250 °C for >20 min prior to a hold at 500 °C.