J. Phys. IV France 123 (2005) 29-34
DOI: 10.1051/jp4:2005123004

Preparation and characterization of the silicon clathrate Na_xSi₁₃₆ (x -> 0)

A. Ammar¹, C. Cros², M. Pouchard², N. Jaussaud², J.-M. Bassat², G. Villeneuve³ and E. Reny<sup>2

1</sup>  Laboratoire du Solide Minéral, Faculté des Sciences Semlalia, Université Cadi-Ayyad, BP. 2390, Avenue Prince Moulay Abdellah, Marrakech, Morocco
²  Institut de Chimie de la Matière Condensée, UPR CNRS 9048, Université de Bordeaux 1, 87 avenue du Docteur Albert Schweitzer, 33608 Pessac Cedex, France
³  UMR 5060 IRAMAT, Université Michel de Montaigne Bordeaux 3 - CNRS, Esplanade des Antilles, 33607 Pessac Cedex, France

Abstract
The type-II silicon clathrate, NaSi₁₃₆, having a residual sodium content as low as 37 ppm (x = 0.0062) has been prepared by thermal decomposition of NaSi under high vacuum in the temperature range 340-420 C followed by subsequent treatments under high vacuum, and completed by several treaments with iodine at 300-350 C. The final sample was characterized by XRD, chemical analysis and EPR spectroscopy. This latter technique proved to be particularly suitable to the characterization of highly diluted sodium atoms in the open host lattice of a type II clathrate of silicon and the quantitaive determination of the residual sodium content

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