Structure and Properties of Magnesium Diboride and the Effect of Additions

Our investigations show that the addition of Ti, polyvalent titanium oxides or TiC powders (0.1-40 mm, amount: 10 wt%) can affect the formation of MgBx (x³4) inclusions and a redistribution of admixed oxygen resulting in the appearance of dispersed inclusions with near MgBO stoichiometry in the MgB2 matrix and thus influencing the critical current density and the critical magnetic fields of the materials. The highest Bc2 and Birr were obtained when powdered polyvalent titanium oxides (synthesized by electroerosion dispersion) or powdered titanium were added, but the critical magnetic fields were somewhat lower in the case of Ti additions. We show that Mg diffuses during the synthesis inside the grains of polyvalent titanium oxide, titanium carbide or titanium, which can affect the redistribution of boron and oxygen in the superconducting matrices and thus influence pinning and the superconducting properties.