Preparation of Guest Free Type II Si–Ge Clathrate Using Ionic Liquid Method

Guest free Type II Si–Ge alloy clathrate exhibits tunable band gap energy depending upon the composition ratio of Si and Ge. In an attempt to synthesize guest free type II Si–Ge alloy clathrates in various Si–Ge compositions, Na4(Si1−yGey)4 precursors were prepared with the variation of y from 0 to 1 and then annealed in a sealed glass tube together with ionic liquid. The obtained samples were characterized by powder XRD experiments and EDX measurements. The synthesis of Si–Ge clathrates were recognized as Si or Ge rich compositions. EDX data and Rietveld analyses of XRD data allowed us to verify the Si–Ge alloy clathrate with low Na content.