Lower-cost thermoelectrics: Thermoelectric materials convert heat to electricity, making them attractive for heat harvesting or cooling applications. However, many high-performance thermoelectrics are made of expensive or toxic materials. He et al. found that a material composed of primarily tin and sulfur could be optimized to have relatively good thermoelectric properties. Introducing about 10% selenium to tin sulfide helped tune these properties by electronic band manipulation. This material is a step toward more earth-abundant, less toxic, and lower-cost thermoelectrics than the telluride-based materials currently in use. Science , this issue p. 1418

In this work, we demonstrate the use of high performance nanostructured PbTe-based materials in high conversion efficiency thermoelectric modules. We fabricated the samples of PbTe–2% MgTe doped with 4% Na and PbTe doped with 0.2% PbI₂ with high thermoelectric figure of merit (ZT) and sintered them with Co–Fe diffusion barriers for use as p- and n-type thermoelectric legs, respectively. Transmission electron microscopy of the PbTe legs reveals two shapes of nanostructures, disk-like and spherical. The reduction in lattice thermal conductivity through nanostructuring gives a ZT of ∼1.8 at 810 K for p-type PbTe and ∼1.4 at 750 K for n-type PbTe. Nanostructured PbTe-based module and segmented-leg module using Bi₂Te₃ and nanostructured PbTe were fabricated and tested with hot-side temperatures up to 873 K in a vacuum. The maximum conversion efficiency of ∼8.8% for a temperature difference (ΔT) of 570 K and ∼11% for a ΔT of 590 K have been demonstrated in the nanostructured PbTe-based module and segmented Bi₂Te₃/nanostructured PbTe module, respectively. Three-dimensional finite-element simulations predict that the maximum conversion efficiency of the nanostructured PbTe-based module and segmented Bi₂Te₃/nanostructured PbTe module reaches 12.2% for a ΔT of 570 K and 15.6% for a ΔT of 590 K respectively, which could be achieved if the electrical and thermal contact between the nanostructured PbTe legs and Cu interconnecting electrodes is further improved.

X-ray structural analysis and high-temperature thermoelectric properties measurements are performed on polycrystalline samples of artificial mineral Cu_12−xNi_xSb₄S₁₃ tetrahedrite. Analysis of the atomic displacement parameter manifests low-energy vibration of Cu(2) out of CuS₃ triangle plane. The vibration results in low lattice thermal conductivity of less than 0.5 W K⁻¹ m⁻¹. By tuning of the Ni composition x and decrease of electronic thermal conductivity, dimensionless thermoelectric figure of merit for x = 1.5 achieves 0.7 at 665 K, which is a considerably high value among p-type Pb-free sulfides. Because the tetrahedrite is an environmentally friendly material, it constitutes a good thermoelectric material for use in support of a sustainable society.

Thermoelectric technology offers the opportunity of direct conversion between heat and electricity, and new and exciting materials that can enable this technology to deliver higher efficiencies have been developed in recent years. This mini-review covers the most promising advances in thermoelectric materials as they pertain to their potential in being implemented in devices and modules with an emphasis on thermoelectric power generation. Classified into three groups in terms of their operating temperature, the thermoelectric materials that are most likely to be used in future devices are briefly discussed. We summarize the state-of-the-art thermoelectric modules/devices, among which nanostructured PbTe modules are particularly highlighted. At the end, key issues and the possible strategies that can help thermoelectric power generation technology move forward are considered. This article is part of a discussion meeting issue ‘Energy materials for a low carbon future’.