Clathrates, i.e. guest-host compounds with cage-like structure, have demonstrated to be promising candidates for the synthesis of new silicon allotropes. Indeed, upon removal of the host element new Si allotropes can be obtained, as in the case of the recently discovered Si₂₄ [1], a new functional material suitable for photovoltaic application obtained from NaSi₆ clathrate [2].

Triggered by the promising results obtained for Na-Si clathrates, different chemical compositions are now explored. For example, the substitution of Na with potassium K offers a higher control on the stoichiometry, improving synthesis efficiency. Control over the flexible stoichiometry and structural variety of Si clathrate would allow us to design new materials with tailored and functional properties.

In this work, we review our recent progresses in the synthesis of K-Si clathrates through in-situ high-pressure synthesis.

[1] Nature Materials 14, 169–173 (2014).

[2] Crystal Growth & Design 13, 303–307 (2013).