Improvement of the thermoelectric properties of GeTe- and SnTe-based semiconductors aided by the engineering based on phase diagram

Abstract

Abstract Group IV–VI semiconductors, such as PbTe, GeTe and SnTe, are promising thermoelectric materials at intermediate temperatures, which have potential application in electrical generation from waste heat. A phase diagram plays an important role for designing a high-performance material. In this mini review, we present the enhancement of the thermoelectric properties of GeTe- and SnTe-based semiconductors based on their phase diagrams. The figure of merit ZT for the p-type GeTe–Ag8GeTe6 composites was enhanced by reducing the thermal conductivity significantly using the eutectic microstructures formed by the Ag8GeTe6 second phase and the GeTe matrix based on the GeTe–Ag8GeTe6 pseudo-binary system. The partial substitution of Te by Se in p-type GeTe extends the solid solubility of Pb in GeTe0.5Se0.5 up to 30 mol.%, which further improves the thermoelectric properties of alloys in the GeTe–PbTe–Se system by modifying the carrier concentration, leading to increasing the Seebeck coefficient and reducing thermal conductivity over a wide composition range. The Sn1−y Mn y Te alloy with 10 at.% excess Mn keeps its composition change along the SnTe–MnTe tie line and receives higher solid solubility of MnTe in SnTe. It shows much higher thermoelectric performance since the excess Mn compensates the Mn lost during the preparation as compared to the Sn1−x Mn x Te alloy without excess Mn.