Mechanochemical formation mechanism of alloyed AgBi-elpasolites

Mechanochemical ball mill synthesis is an emerging method for producing complex materials, including alloyed halide elpasolite semiconductors. This solvent-free method offers precise control over chemical composition, enabling fine-tuning of optical and mechanical properties. However, the formation mechanism of alloyed elpasolites remains unclear. In this work, we elucidate the crystallization kinetics of mechanochemical formation of Cs2AgBi0.5M0.5Br6 [M = Sb3+, In3+, or Fe3+] using in situ synchrotron X-Ray diffraction experiments. We identify the reaction intermediates for the parent composition Cs2AgBiBr6, and find that –Bi0.5Sb0.5– forms via a similar reaction pathway. Alloying with In3+ or Fe3+ on the other hand occurs via an additional cation-exchange step. These insights into the mechanochemical formation mechanisms of alloyed AgBi-elpasolites provide guidelines towards rational compositional engineering of complex materials.