Mechanical alloying as a new synthesis route for metastable silicon clathrates

Stability studies by ab-initio calculations for the best-known binary Ba-Si clathrates reveal that Ba24Si100 is the most stable composition and that the latter can be stabilized in a relatively small energy range, of the order of a few kJ/mol.at. This suggested alternative synthesis routes, easier and cheaper to the commonly used high pressure-high temperature processes. Here, for the first time, we confirmed the theoretical prediction and were successful in the synthesis of the phase Ba24Si100 by mechanical alloying. The influence of the milling parameters is discussed in order to get a crystalline phase with 90% purity.