Phase Formation of Iron-Based Superconductors during Mechanical Alloying.

We successfully synthesized bulk Ba_0.6Na_0.4Fe₂As₂ and Sr_0.5Na_0.5Fe₂As₂ compounds by high-energy mechanical alloying (MA) technique. The MA process results in homogeneous amorphous phases of BaFe₂As₂ and SrFe₂As₂. It was found that the optimum time for high-energy milling in all cases is about 1.5–2 h, and the maximum amount of amorphous phase could be obtained when energy of 50–100 MJ/kg was absorbed by the powder. After a short-term heat treatment, we obtained nearly optimum sodium-doped Ba_1−xNa_xFe₂As₂ and Sr_1−xNa_xFe₂As₂ superconducting bulk samples. Therefore, MA is a potential scalable method to produce bulk superconducting material for industrial needs. [ABSTRACT FROM AUTHOR]