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

Nanostructural superconducting MgB 2 -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 (j c =10 6 A/cm 2 in 1 T at 20 K), upper critical magnetic fields (B c2 (0 K)= 42 T, B c2 (22 K)= 15 T) and the fields of irreversibility (B ρ (0 K)= 32.5 T, B ρ (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.