n- and p-Type behaviour of the gold-substituted type-I clathrate, Ba8AuxSi46–x (x = 5.4 and 5.9)

Abstract Two samples of the gold-substituted silicon clathrate, Ba 8 Au x Si 46– x , have been synthesized from the elements at high temperature, one without subsequent treatment (so-called AG for as-grown) and the other after annealing in a silica tube (so-called A for annealed). A structure analysis on single crystal of both samples shows that the x Au content for the AG and A sample is 5.4 and 5.9, respectively. Both samples have been characterized by Seebeck coefficient and electrical conductivity measurements, as well as by 29 Si MAS NMR spectroscopy. The AG sample is an n-type semi conductor close to a metal, whereas the A one exhibits a p-type metallic behaviour. The NMR spectra are consistent with a high contribution to the conductivity of the Si(3s) orbitals at the Fermi level. To cite this article: N. Jaussaud et al., C. R. Chimie 8 (2005) .