Structure and Properties of MgB2: Effect of Ti-O and TiC Additions

The effects of the additions of powdered titanium carbide (TiC) and polyvalent titanium oxides (Ti-O) to MgB2 (synthesized under high pressure (2 GPa)-high temperature (800 and 1050 °C) conditions) on the critical current density, jc, critical magnetic fields, B C2 and Birr, and the related transformations in the materials structures are reported in this paper. The superconducting characteristics are compared with that of MgB2 with titanium (Ti) additions synthesized under the same conditions. The synthesis temperature, the ability of Ti-containing compounds to act as a getter, and the different diffusion rates of Mg and B into grains of these additions influence the distribution of the elements (boron, magnesium, and impurity oxygen) in the structures of MgB2-based materials. This in turn affects the formation of pinning centers, the resulting flux pinning and eventually the superconducting properties (jc, BC2, B irr).