MAGNESIUM OXIDE UPTAKE IN Mg2Si THERMOELECTRIC PELLETS AND THEIR PROTECTION BY THIN COATING AT MIDDLE-HIGH TEMPERATURES

The magnesium silicide (Mg2Si) based alloys are promising candidates for thermoelectric (TE) energy conversion in the middle-high temperature range. These materials are a candidate to replace lead-based TE materials due to the abundance of their constituent elements in the earth's crust, their nontoxicity and their low density [1]. The drawback of such kind of materials is their oxygen sensitivity at high temperature [2, 3] that entails their use under vacuum or inert atmosphere. In this work, the influence of pellet features on the MgO uptake and the protection of the silicide pellets, coated via magnetron sputtering, are discussed. X-Ray Diffraction, Energy Dispersive Spectroscopy, Field Emission Scanning Electron microscope (FE-SEM), themorgravimetric analysis, and electrical measurement at high temperature were carried out in order to obtain, respectively, the structural, compositional, morphological and electrical characterization of the pellets and coatings. The mechanical behavior of the system thin film/Mg2Si-substrate as a function of temperature and the coating barrier properties for oxygen protection were qualitatively evaluated by FE-SEM after thermal treatment in air at high temperature. References [1] T. Sakamoto, T. Iida, N. Fukushima, Y. Honda, M. Tada, Y. Taguchi, Y. Mito, H. Taguchi, Y. Takanashi, Thin Solid Films, 519 (2011) 8528-8531. [2] J. Tani, M. Takahashi, H. Kido, Thermoelectric properties and oxidation behaviour of Magnesium Silicide, in, Osaka, 2011. [3] S. Battiston, S. Boldrini, S. Fiameni, A. Famengo, M. Fabrizio, S. Barison, Thin Solid Films, 526 (2012) 150-154.