Band and scattering tuning for high performance thermoelectric Sn1−xMnxTe alloys

The thermoelectric figure of merit zT of SnTe, an analogue to PbTe, has long been known to be about 0.6, mainly due to its single band transport behavior. Similar to what has been found in PbTe, alloying with group II monotellurides such as CdTe, HgTe, MgTe enables a reduced energy separation between the two valence bands of SnTe, leading to converged bands for a significantly increased zT to ∼1.1 with demonstrated further improvements by other independent strategies such as nanostructuring. Here we show alloying with highly soluble MnTe not only tunes the band structure but also reduces the lattice thermal conductivity, leading to a record zT of ∼1.3 at 900 K in the alloy form that does not rely on additional mechanisms for lattice thermal conductivity reduction. This work demonstrates Sn1−xMnxTe as a potential alternative for PbTe with toxic Pb.

According to our previous experiences on successful manipulation of band structure by alloying, this work is motivated by a heavily alloying strategy for aligning the bands from the well-separated ones in pristine SnTe. The resulting well-aligned conducting channels (bands) for charge carriers and high-concentration blocking centers for heat carriers (phonons) propagation, lead to a record thermoelectric figure of merit, zT = 1.3 in SnTe alloys. Most importantly, the obtained high performance does not rely on any other independent strategies than alloying for even lower thermal conductivity, enabling a bright future for a further improvement.Figure optionsDownload as PowerPoint slide