On the power factor of bismuth-telluride-based alloys near topological phase transitions at high pressures

The Seebeck coefficient $S$ and electrical conductivity $\sigma$ of bismuth-telluride-based alloys with substituents in the Bi and Te sublattices are studied at pressures up to 12 GPa at room temperature. It is shown that the electrical conductivity increases with pressure and, despite a decrease in the Seebeck coefficient, the power factor $S^2\sigma$ increases in $p$-Bi$_{0.5}$Sb$_{1.5}$Te$_{3}$ and $n$-Bi$_{2}$Te$_{1.65}$Se$_{0.65}$S$_{0.7}$ alloys. A maximum increase in the power factor is observed for $n$-Bi$_{2}$Te$_{1.65}$Se$_{0.65}$S$_{0.7}$ in the pressure range of 3–4 GPa corresponding to the electronic topological phase transition. The studied alloys are used in modeling the thermoelectric module with adjustable mechanical stress applied to thermoelements.