Methodology for synthesis of 12442 family iron-based stoichiometric superconductors: KCa2Fe4As4F2, RbCa2Fe4As4F2, CsCa2Fe4As4F2

The paper describes a method of synthesis of polycrystalline samples of iron-based stoichiometric high-temperature superconductors of the 12442 family: KCa2Fe4As4F2, RbCa2Fe4As4F2 and CsCa2Fe4As4F2, by mechanical alloying using a cryomill. The described technique allows to obtain polycrystalline samples with impurities content not more than 1 wt.% due to optimization of milling time and temperature profile, and the use of mechanical alloying allows to reduce the synthesis time significantly.