Pinning behavior in bulk MgB2 prepared using boron powder refined via high-energy ultra-sonication

We successfully refined a cheap commercial boron powder by means of high-energy ultra-sonication and utilized it in synthesis of bulk MgB2. Rietveld phase analysis of X-ray diffraction pattern revealed completely formed MgB2 with a low amount of MgO. MgB2 bulk prepared of boron ultra-sonicated in ethanol for 15 min showed self-field J(c) of around 300 kA/cm(2) at 20 K without any compromise in T-c (similar to 39 K). Pinning analysis based on Dew-Hughes expression showed major pinning contribution from grain-boundary pinning (similar to 95.5%), along with a slight contribution from point pinning (4.5%). The microstructure study detected a system of large MgB2 grains (hundreds nm large) and 10-20 nm sized particles, possibly Mg-B-O, formed at MgB2 grain boundaries.