Thermal stability of n-type zone-melting Bi2(Te, Se)3 alloys for thermoelectric generation

Bi2Te3 based alloys are now starting to be used in thermoelectric power generation (TEG). The thermal stability plays a very important role in long-term high temperature environments. In this work, we investigated the thermal stability of n-type zone-melting Bi2Te2.79Se0.21 alloys under various service temperatures and time. The n-type Bi2Te2.79Se0.21 alloys possessed excellent structural stability below 573 K, but the figure of merit gradually decreased as a result of the increasing electrical resistivity and thermal conductivity. Unfortunately, as the annealing temperature and time increased further, the volatilization of Te (Se) caused more defects and resulted in the decrease of density and a slight volume expansion of n-type Bi2Te2.79Se0.21 alloys. At the same time, its thermoelectric performance had further deteriorated. Moreover, what is particularly noteworthy is that the annealing process can effectively enhance the texture of the zone - melting ingots due to the decreased dislocation density, which was rarely reported in the previous reports for thermoelectric materials.