Examination of oxidation resistance of Mg2Si thermoelectric modules at practical operating temperature

Magnesium silicide (Mg2Si) is as known a thermoelectric material with low environmental load and high power factor around 400 °C. It should be performed to solve the problems. i.e., its low oxidation resistance and high chemical activity. In the current decades, oxidation resistance of Mg2Si has been researched because it is essential to thermoelectric power generation. The oxidation factor of Mg2Si still remains unexplained. In this paper, forming process of oxidation resistant layer of Mg2Si powder is examined by thermal analysis and X-ray diffraction. It was revealed that Mg2Si induced to compound with elements of the atmosphere. The oxidation process of Mg2Si was related to humidity without oxide, since oxidation layer absorbs humidity and forms a magnesium hydroxide (Mg(OH)2) layer. The Mg(OH)2 layer was decomposed at 400 °C, which is the temperature required for practical use of thermoelectric generation. It is found that a humidity resistant layer should be formed on the surface of Mg2Si.