Oxidation suppression characteristics of the YSZ coating on Mg 2 Si thermoelectric legs

Abstract Oxide-based coating layers were investigated to suppress the oxidation of an intermediate temperature thermoelectric module that operates in a temperature range of 300–700 °C. Four different oxides [alumina (Al 2 O 3 ), yttria (Y 2 O 3 ), 8 mol% yttria-stabilized zirconia ((Y 2 O 3 ) 0.08 (ZrO 2 ) 0.92 , YSZ), and 20 mol% samaria-doped ceria (Sm 0.2 Ce 0.8 O 1.9 , SDC)] were coated onto Mg 2 Si thermoelectric leg surfaces and their anti-oxidation characteristics were compared. While Al 2 O 3 , Y 2 O 3 , and SDC layers failed to prevent the progression of oxidation of the thermoelectric Mg 2 Si surface at 700 °C, YSZ showed potential as an anti-oxidation coating layer for intermediate temperature thermoelectric modules. The apparent oxidation suppression characteristics of the YSZ layer on the Mg 2 Si thermoelectric material were studied by a microstructural investigation of the interface between the coated layer and the thermoelectric material. The reliability of the YSZ coating structure was investigated via thermal cycling tests from room temperature to 600 °C. The practical adaptability of the YSZ anti-oxidation coating in terms of use for thermoelectric power-generation modules is discussed in detail with the results of variation in contact resistance.