Phase Formation of Iron-Based Superconductors during Mechanical Alloying.

We successfully synthesized bulk Ba 0.6 Na 0.4 Fe 2 As 2 and Sr 0.5 Na 0.5 Fe 2 As 2 compounds by high-energy mechanical alloying (MA) technique. The MA process results in homogeneous amorphous phases of BaFe 2 As 2 and SrFe 2 As 2 . 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-x Na x Fe 2 As 2 and Sr 1-x Na x Fe 2 As 2 superconducting bulk samples. Therefore, MA is a potential scalable method to produce bulk superconducting material for industrial needs.