Influence of extra magnesium on the Nb-B interface and superconducting properties of MgB2/Nb tapes

► Excessive Mg in MgB2/Nb tapes could slow down the Nb-B diffusion to some degree. ► The suitable amount of extra Mg in Mg1+xB2/Nb tapes differs between x = 0.03 and 0.05 depending on the sintering temperatures. ► Over sufficient Mg in Mg1+xB2/Nb tapes would accelerate the Nb-B diffusion due to Mg steam pressure.