Effects on phase transition and thermoelectric properties in the Pb-doped GeTe-Bi2Te3 alloys with thermal annealing

Abstract

The phase-transition behavior in GeTe-based alloys has been intensively studied recently for enhancing their thermoelectric performance. In this study, thermal annealing induced phase transition and corresponding effects on the thermoelectric properties of Pb-doped GeTe-Bi2Te3 alloys were systematically studied. By Pb doping, the lattice thermal conductivity of (GexPb1-xTe)0.93(Bi2Te3)0.07 alloys were significantly reduced due to the strong phonon scattering from point defects and stacking faults, resulting in a peak thermoelectric figure of merit ZT of ∼1.47 at 673 K for the (Ge0.84Pb0.16Te)0.93(Bi2Te3)0.07. By thermal annealing, the structure of GeTe-Bi2Te3 alloys can be shifted from pseudo-cubic to rhombohedral phase, and corresponding induced lattice distortion and microstructures can further reduce the lattice thermal conductivity. The thermal annealing can also lead to the increase of hole concentration and carrier mobility of the GeTe-based alloys. Our results proved the significance of thermal annealing treatment for tuning the microstructures and thermoelectric properties in the GeTe based alloys with phase-transition behavior.