Synthesis of the Clathrate-I Phase Ba8-xSi46 via Redox Reactions

The clathrate-I phase Ba8-xSi46 (space group Pm (3) over barn) was synthesized by oxidation of Ba4Li2Si6 with gaseous HCl. Microcrystalline powders of the clathrate phase were obtained within a few minutes. The reaction temperature and the pressure of HCl were optimized to achieve good-quality crystalline products with a composition range of 1.3 < x < 1.9. The new preparation route presented here provides an alternative to the high-pressure synthesis applied so far.