The Clathrate Ba 8– x Si 46 Revisited: Preparation Routes, Electrical and Thermal Transport Properties

The clathrate‐I Ba 8– x Si 46 was manufactured from BaSi 2 and α‐Si by high‐pressure high‐temperature synthesis at 5 GPa and 900 °C and by redox reaction from Ba 4 Li 2 Si 6 . The transport properties were measured on specimens from the high‐pressure high‐temperature synthesis. The composition of the Ba 8– x Si 46 phase [space group Pm $\bar{3}$ n , a = 10.3051(1) Å] corresponds to x = 0.8(2) according to the refined lattice parameter, the value determined from full‐profile refinement of powder X‐ray diffraction data amounts to x = 0.73(1), and the chemical analysis results in x = 1.0(1), yielding the average composition Ba 7.2(2) Si 46 . The electrical transport properties of the phase with x = 0.8 were determined in the temperature range 2–300 K using a polycrystalline bulk specimen. The material is a metallic conductor with ρ (300 K) = 3.3 μΩ m and S (300 K) = –6.8 μV K –1 . The thermal conductivity shows a relatively large – for an intermetallic clathrate – value of about 8 W · K –1 m –1 .