Boron powder purification and its effects on the microstructure and superconducting properties of MgB$_{2}$.

MgB$_{2}$ wires can be easily fabricated by reacting Mg powder with amorphous boron powder. But commercial boron powder normally contains impurities such as B$_{2}$O$_{3}$. The presence of B$_{2}$O$_{3}$ could lead to the formation of oxides in MgB$_{2}$ wire, which may reduce the connectivity. In this work, B$_{2}$O$_{3}$ in amorphous boron powder was removed. MgB$_{2}$ samples were made both from purified and unpurified boron powders. X-ray diffraction showed that removing B$_{2}$O$_{3}$ in the boron powder resulted in a significant decrease in the content of MgO in the sample. The effects of boron powder purification on microstructure, critical temperature, critical field and connectivity will be presented.