Synthesizing thermoelectric materials to contribute to sustainable power generation

Semiconducting clathrates are considered to be promising thermoelectric materials because of their low heat conductivity, which is believed to be due to its cage structure. Weakly bonded filler atoms in the cages are expected to disturb the heat transport (phonons) in the crystal by thermal “rattling” in the cages.

Baitinger et al. provide a complete thermoelectric characterization of clathrate Ba_8-dAu_5.33Ge_40.67, which features both a strong bonding of the filler atoms to the cage (Ba-Au bonds) and surprisingly long phonon lifetimes. Its thermoelectric properties suggest its applications to recovering and recycling waste heat.

“The general motivation to study thermoelectric materials is to contribute to sustainable power generation,” said author Michael Baitinger. “Our work wanted to investigate the complete procedure starting from a simple but highly reproducible preparation to the integration of the material in a small thermoelectric module.”

The researchers developed a simple synthesis technique for the thermoelectric material. Despite the large-scale preparation, the physical properties were highly reproducible for samples so similar in composition that they can hardly be distinguished by X-ray diffraction.

They suggested a soldering procedure by introducing inert diffusion barriers, such as carbon. They integrated eight module blocks to a 1-square-inch test generator, delivering a power of 0.2 W for a temperature difference of 380 K.

Preparation was optimized for the material and allows control of the properties on a 100 g scale. The sample itself is a clathrate phase with a different kind of heat conduction than usually expected for intermetallic clathrates.

“We hope that more papers will consider the suitability of thermoelectric materials not only from one selected optimized laboratory sample but also consider other aspects like soldering and module fabrication,” said Baitinger.

Source: “Thermoelectric characterization of the clathrate-I solid solution Ba_8-dAu_xGe_46-x,” by Michael Baitinger, Hong Duong Nguyen, Christophe Candolfi, Iryna Antonyshyn, Katrin Meier-Kirchner, Igor Veremchuk, Valeriy Razinkov, Mykola Havryluk, Raul Cardoso-Gil, Ulrich Burkhardt, Bodo Böhme, Lukyan Anatychuk, and Yuri Grin, Applied Physics Letters (2021). The article can be accessed at https://doi.org/10.1063/5.0059166 .

This paper is part of the Thermoelectric Materials Science and Technology Towards Applications Collection, learn more here .