Co-addition of nano-carbon and nano-silica: An effective method for improving the in-field properties of magnesium diboride superconductor

Abstract

MgB₂ superconductor sample co-doped with nano-carbon (n-C) and nano-silica (n-SiO₂) is prepared and its structural and superconducting properties are compared with pure and n-C and nano SiC (n-SiC) mono-doped samples. Shrinkage of a-lattice parameter is observed for all doped samples, among which the co-doped sample exhibits the maximum shrinkage, an evidence of effective carbon substitution at boron sites. All doped samples show significantly enhanced in-field critical current density JC(H), where the co-doped sample dominates others throughout the whole range of field studied. Lattice strains induced by carbon substitution and flux pinning caused by uniformly distributed nano sized Mg₂Si particles formed by the reaction between Mg and n-SiO₂, are the main reasons for the highly enhanced JC(H) behavior of the co-doped superconductor.