Na substitution effects on MgB2 synthesized with a microwave-assisted technique

The effect of different Na doping levels on structural and electric transport properties MgB2 of bulk samples was investigated. The samples were synthesized by an assisted microwave method using the microwave radiation to heat the powder precursors (Mg and B, high purity) constrained in a stainless steel box. It was found that Na addition induces a small X-ray diffraction peak broadening. Moreover a slight decreasing of the critical temperature and an improvement of both the irreversibility field and the upper critical field are exhibited. The result is almost independent on the doping level. The pinning energy turns out to be higher for the doped samples even if its dependence on current and temperature is the same for doped and undoped samples. Doping effect, flux pinning, magnesium diboride, microwave synthesis, structural characterization.