Thermal stability of p-type polycrystalline Bi2Te3-based bulks for the application on thermoelectric power generation

In the present work, the thermal stabilities of p-type polycrystalline Bi0.44Sb1.56Te3 bulks have been investigated at different temperatures in vacuum environment. The effect of service temperature on the microstructure, thermoelectric and mechanical properties of Bi0.44Sb1.56Te3 bulks were investigated in detail. The results showed that the service temperature below 473 K had no obvious influence on the grain size, the crystal lattice constant, the density and the corresponding thermoelectric properties, and p-type Bi0.44Sb1.56Te3 based bulks could maintain good thermal stability below 473 K. Nevertheless, when the service temperature was over 523 K, the volume expansion began to accelerate, the increasingly obvious mass loss presented due to drastic Te volatilization, and the density of the bulks decreased notably, which resulted in the obvious increase of resistivity and a serious decline in the power factor as service temperature increased, although the Seebeck coefficient presented a slight increase. More seriously, the mechanical properties of the Bi0.44Sb1.56Te3 bulks degraded seriously when the service temperature was above 523 K. All evidences implied that the Bi0.44Sb1.56Te3 bulks could be stabilized at service temperature of 473 K, the thermoelectric and mechanical properties would get worse obviously when the service temperature was over 523 K. Therefore, the highest service temperature of Bi2Te3 based thermoelectric power generation modules could not exceed 473 K. [Display omitted] •The thermal stability of p-type Bi2Te3 based bulks were investigated in detail.•The p-type Bi2Te3 based bulks could maintain good thermal stability below 473 K.•The volume expansion and mass loss rate increased, and density decreased over 523 K.•The thermoelectric and mechanical properties would obviously degrade over 523 K.•For p-type Bi2Te3 based bulks, higher service temperature was, lower hardness was.