Mechanochemically assisted low temperature synthesis route of the 1144 Ca-K Iron Based Superconductor

Among the Iron Based Superconductors, the so-called 1144 family attracts significant interest due to its high critical fields and critical current densities and to the stoichiometric nature of the compounds, disentangling the superconducting properties from the compositional homogeneity. Their practical application is partly hindered by the severe and strict synthesis conditions, complicated by high temperature (T > 900 °C) treatments of volatile and toxic elements. In this work, a milder synthetic approach to produce 1144 materials is proposed. A simple one-step High Energy Ball Milling treatment of the pure elements is coupled to a low temperature (i.e. 600 °C) thermal treatment to produce the superconducting Ca/K-1144 material, characterized by a good degree of homogeneity and critical temperatures higher than 30 K. The results here reported demonstrate the previously excluded feasibility of a simple and easily scalable lower temperature synthesis route for a Ca/K-1144 compound. We suggest that the intimate mixing and dispersion of the starting elements promoted by the mechanochemical treatment constitutes a key factor for the successful lowering of the synthesis temperature.