Salt Flux Synthetic Catholicon: A Universal Route to Refractory and High-Entropy Alloys and Intermetallics.

Intermetallic compounds and multicomponent refractory alloys exhibit numerous applications in catalysis, magnetism, and energy conversion, yet their synthesis remains challenging due to the refractory nature of their constituent elements and inherently sluggish nature of solid-state diffusion that requires extreme reaction temperatures. Herein, we introduce a general CsCl-mediated molten-salt synthetic method that enables single-step, moderate-temperature (<1050 °C) access to finely dispersed single-phase polycrystalline metallic materials across diverse structural families. Binary alloys with melting temperatures over 2000 °C, Laves-type intermetallics, the incongruently melting complex intermetallics such as μ-phase Fe7Mo6, and multimetallic high-entropy alloys (HEAs) were successfully prepared by this facile method. For Fe7Mo6, the synthesis enabled further characterization of magnetic and electrocatalytic properties. The CsCl flux mediates a dissolution-reprecipitation pathway that yields homogeneous polycrystalline powders with controlled stoichiometry. Such alloys and intermetallics can be further converted to corresponding multimetallic MXides, while preserving metal stoichiometry, as demonstrated for phosphides, carbides, borides, and sulfides. Overall, this work establishes a robust and scalable synthetic platform for the facile synthesis of compositionally and structurally diverse refractory multimetallic systems.