Improved Thermoelectric Properties of BiSbTe-AgBiSe₂ Alloys by Suppressing Bipolar Excitation

Bismuth telluride alloys are the only commercialized thermoelectric materials, which have successfully realized the practical applications of active cooling and waste heat harvesting near room temperature. However, the drawbacks of intermediate ZT values and brittle nature of zone-melted materials have limited their future development. Herein, we show that AgBiSe2 alloying is an effective approach to improve both the thermoelectric and mechanical performance of sintered Bi0.48Sb1.52Te3 materials. The addition of AgBiSe2 can not only suppress the bipolar effect by increasing the hole concentration but also decrease the lattice thermal conductivity by introducing various phonon scattering centers. These effects enable a peak ZT value of 1.1 at 375 K and an average value of 0.94 between 300 and 500 K in the composite of Bi0.48Sb1.52Te3-0.3 wt % AgBiSe2. Moreover, the addition of AgBiSe2 can also enhance the Vickers hardness, which reaches 0.75 GPa, 42% times higher than that of pristine zone-melted BiSbTe.