Magnesium diboride was synthesized and its structure confirmed in 1953. The simplest synthesis involves high temperature reaction between boron and magnesium powders. Formation begins at 650 °C; however, since magnesium metal melts at 652 °C, the reaction may involve diffusion of magnesium vapor across boron grain boundaries. At conventional reaction temperatures, sintering is minimal, although grain recrystallization is sufficient for Josephson quantum tunnelling between grains.
Superconducting magnesium diboride wire can be produced through the powder-in-tube (PIT) ex situ and in situ processes. In the in situ variant, a mixture of boron and magnesium is reduced in diameter by conventional wire drawing. The wire is then heated to the reaction temperature to form MgB. In the ex situ variant, the tube is filled with MgB powder, reduced in diameter, and sintered at 800 to 1000 °C. In both cases, later hot isostatic pressing at approximately 950 °C further improves the properties.
An alternative technique, disclosed in 2003, employs reactive liquid infiltration of magnesium inside a granular preform of boron powders and was called Mg-RLI technique. The method allowed the manufacture of both high density (more than 90% of the theoretical density for MgB) bulk materials and special hollow fibers. This method is equivalent to similar melt growth based methods such as the Infiltration and Growth Processing method used to fabricate bulk YBCO superconductors where the non-superconducting YBaCuO is used as granular preform inside which YBCO based liquid phases are infiltrated to make superconductive YBCO bulk. This method has been copied and adapted for MgB and rebranded as Reactive Mg Liquid Infiltration. The process of Reactive Mg Liquid Infiltration in a boron preform to obtain MgB has been a subject of patent applications by the Italian company Edison S.p.A.
Hybrid physical–chemical vapor deposition (HPCVD) has been the most effective technique for depositing magnesium diboride (MgB) thin films. The surfaces of MgB films deposited by other technologies are usually rough and non-stoichiometric. In contrast, the HPCVD system can grow high-quality in situ pure MgB films with smooth surfaces, which are required to make reproducible uniform Josephson junctions, the fundamental element of superconducting circuits.