Oxidation and sublimation suppression of PbTe thermoelectric legs by plasma coated ceramic layers

Abstract

Plasma sprayed ceramic coating layers were investigated for use in suppressing the oxidation and sublimation of intermediate temperature PbTe thermoelectric legs (usually operated in the temperature range of 300-700 degrees C). The authors used two different oxides for the comparison of their antioxidation characteristics. One is yttria (Y2O3) and the other is 8mol. % yttria-stabilized zirconia [(Y2O3)(0.08)(ZrO2)(0.92), YSZ]. Both oxides were coated by plasma spray method on the surfaces of the PbTe thermoelectric legs, respectively. As a result, the Y2O3 coating layers could not prevent the progression of oxidation in the thermoelectric PbTe surfaces at 500 degrees C, but the YSZ coating layers showed a relatively high resistance enough to prevent the progression of oxidation, which is promising for intermediate-temperature thermoelectric modules. The x-ray diffraction and x-ray photoelectron spectroscopy investigations revealed that the YSZ-coating of PbTe thermoelectric legs led to the formation of the secondary oxide phase layers that help to prevent the oxidation during the heat treatment. Overall, the reliability and electrical properties of the YSZ-coated PbTe thermoelectric legs were investigated. Finally, the authors expect that this work will be useful for the future intermediate-temperature thermoelectric modules in the future. (C) 2016 American Vacuum Society.