Hygrothermal Stability of Bi2Te3-based Thermoelectric Materials

Bi2Te3-based thermoelectric (TE) materials have already been commercialized, of which the hygrothermal stability has a direct impact on the service reliability of TE devices, but is still confronted many challenges. This work investigated the degradation behavior of commercial n-type Bi2Se0.21Te2.79 and p-type Bi0.4Sb1.6Te3 TE materials during storage in 85., 85% RH hygrothermal environment for 600 h. The surfaces of n-type Bi2Se0.21Te2.79 and p-type Bi0.4Sb1.6Te3 TE materials were oxidized with reaction process of Bi2Te3+O-2.Bi2O3+TeO2 and Bi2Te3+Sb2Te3+O-2 -> Bi2O3+Sb2O3+TeO2, respectively. The oxidation process creates nanoscale holes and even microcracks inside the material, which leads to an overall deterioration of the electrical and thermal properties. At room temperature, the electrical conductivity of the n-type Bi2Se0.21Te2.79 material drops from 9.45x10(4) S center dot m(-1) to 7.79x10(4) S center dot m(-1) after exposure, and ZT decreases from 0.97 to 0.79, while Seebeck coefficient of the p-type Bi0.4Sb1.6Te3 material declines from 243 mu V center dot K-1 to 220 mu V center dot K-1, correspondingly, ZT decreases from 1.24 to 0.97. In conclusion, Bi2Te3-based TE materials have extremely poor hygrothermal stability, and their corresponding micro-TE devices need to be strictly encapsulated in service to prevent complex redox reactions between the TE materials themselves and the environmental water vapor and