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I. Zeiringer, E. Bauer, A. Grytsiv, P. Rogl, H. Effenberger:
"Phase Equilibria, Crystal Chemistry, and Physical Properties of Ag-Ba-Si Clathrates";
Japanese Journal of Applied Physics, 50 (2011), 05AF01; S. 1 - 4.

In the Ag-Ba-Si system the clathrate type I solid solution, Ba8AgxSi46-x, ranges at 800 °C from Ba8Ag4.3Si41.7 [a = 1.04309(3) nm] to Ba8Ag5.4Si40.6 [a = 1.04613(5) nm]. For all clathrate compositions in this homogeneity region (4.3 ≤x ≤5.4) cubic primitive symmetry with space group Pm3n was confirmed by X-ray powder diffraction assisted by X-ray single crystal analyses of Ba8Ag4.9Si41.1. Site preference from X-ray refinement reveals that silver atoms preferably occupy the 6d site in random mixture with Si. Ba2AgSi3 (Ba4Li2Si6 type, Fddd, a = 0.862, b = 1.493, and c = 1.965 nm), reported by Cardoso et al., was confirmed. Studies of transport properties for Ba8Ag5Si41 evidenced electrons as predominant charge carriers and the closeness of the system to a metal-to-insulator transition.

http://dx.doi.org/10.1143/JJAP.50.05FA01