Influence of oxygen and boron distribution on superconducting characteristics of nanostructural Mg-B-O ceramics

Nanostructural superconducting MgB2-based materials contain a great quantity of O, which gives grounds to assign them to Mg-B-O compounds. The quantity of O in these materials is not an obstacle for attaining high critical current density (jc=10⁶ A/cm² in 1 T at 20 K), upper critical magnetic fields (Bc2(0 K)= 42 T, Bc2(22 K)= 15 T) and the fields of irreversibility (Bρ(0 K)= 32.5 T, Bρ(18.5 K)= 15 T). Our recent studies have shown that by changing manufacturing conditions (temperature, pressure, adding Ti, SiC) is possible to affect oxygen and boron distribution in the structure of Mg-B-O ceramic materials and purposefully change the type of pinning, superconducting properties, thus varying their behavior in magnetic fields.