  The study of high pressure (2 GPa) synthesized MgB2-based materials allows us
to conclude that higher borides (with near MgB12 stoichiometry) and
oxygen-enriched Mg-B-O inclusions can be pinning centers in nanostructural
magnesium diboride matrix (with average grain sizes of 15-37 nm). It has been
established that additions of Ti or SiC as well as manufacturing temperature
can affect the size, amount and distribution of these inclusions in the
material structure and thus, influence critical current density. The
superconducting behavior of materials with near MgB12 stoichiometry of matrix
is discussed.
