Preparation and characterization of MgB₂ polycrystalline with different milling method

In this study, we focus on the synthesis of MgB₂ polycrystalline by using three different methods. MgB₂ polycrystalline was prepared by conventional and mechanical alloying method. Three variations of milling method were used, which are agate mortar for a half hour; High energy ball milling (HEBM) under air atmosphere for 2 hours; and HEBM under argon for 2 hours. MgB2 polycrystalline was prepared using magnesium and boron powder with a ratio of Mg:B =1:2. After milling, the mixed powders were poured into a stainless steel SS304 tube, compacted by the press machine and sintered at 800°C for an hour in an air atmosphere. After sintering, the sample was removed from the tubes and analyzed the phase formation, microstructure, resistivity and critical temperature (Tc) of the samples. Hexagonal phase MgB₂ can be seen as a dominant phase for all samples based on a qualitative analysis of X-Ray Diffraction (XRD), but there was a small amount of Mg and MgO phase as impurities. We obtained the qualitative and quantitative analysis of sample mixed with the agate mortar was the optimal sample with less impurity phase compared to other samples. Sample by using HEBM under air has the highest T_Conset of 42.3 K and T_Czero of 41.9 K.