Lead-free GeTe alloys with high thermoelectric performance for low-grade waste heat energy harvesting

Abstract

<p>Harvesting and utilization of low-grade waste heat dissipated from industries have garnered immense attention in recent years. Thermoelectric materials, which can directly convert heat into electricity, provide an eco-friendly solution for waste heat recovery. Recently, GeTe-based materials have developed as strong competitors to Bi2Te3 near room temperature. Nonetheless, despite exhibiting comparable thermoelectric performance, the majority of these GeTe alloys incorporate toxic Pb, thus limiting the practical application. Herein, a boosted zT was achieved in Ge0.93Bi0.05Te over the entire temperature range by introducing Ge deficiency. Further AgSbTe2 alloying leads to a remarkable increase in density-of-states effective mass and high weighted mobility. Thermally, the addition of AgSbTe2 forms various phonon scattering centers including domain structures, dislocations, and phase boundaries, contributing to the low lattice thermal conductivity. As a result, a high average zT of 1.34 (323–573 K) is obtained in the lead-free (Ge0.93Bi0.05Te)85(AgSbTe2)15 material, and its maximum single-leg conversion efficiency reaches 8.6 % at ΔT = 273 K. The outstanding thermoelectric performance and the lead-free characteristic presented in our study shed light on the potential of GeTe alloys for applications in recovering low-grade waste heat.</p>