Effect of carbon doping on the formation and stability of MgB₂ phase

We have investigated the phase evolution and microstructure of carbon doped MgB₂ by using differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscope (SEM). The analysis of DSC and XRD indicate that both the reaction temperature between Mg and B and the MgB₂ phase stability increase for the carbon doped samples. The reaction rate between Mg and B decreases with the carbon content increase in the Mg-B system. SEM observation has shown that the carbon doping degenerates the grain connectivity of MgB₂. In order to improve denseness of MgB₂ sample, the two-step reaction method is proposed.