Wissenschaftler stellen Kristalle her, die aus Wärme Strom erzeugen

Ein synthetisches Sulfidmineral mit thermoelektrischen Eigenschaften.

Im Bestreben, Wärme effizient in Strom umzuwandeln, eröffnen leicht zugängliche Materialien aus unbedenklichen Rohstoffen neue Perspektiven bei der Entwicklung von sicheren und kostengünstigen sogenannten thermoelektrischen Materialien. Laut einer kürzlich in der Zeitschrift veröffentlichten Studie erhält ein synthetisches Kupfermineral durch einfache Änderungen seiner Zusammensetzung eine komplexe Struktur und Mikrostruktur, die den Grundstein für die gewünschten Eigenschaften legt Angewandte Chemie.

Das neue synthetische Material besteht aus Kupfer, Mangan, Germanium und Schwefel und wird durch einen ziemlich einfachen Prozess hergestellt, erklärt der Materialwissenschaftler Emmanuel Guilmeau, CNRS-Forscher am CRISMAT-Labor in Caen, Frankreich, der der korrespondierende Autor der Studie ist . . „Die Pulver werden einfach durch Kugelmahlen mechanisch legiert, um eine vorkristallisierte Phase zu bilden, die dann bei 600 Grad verdichtet wird.[{“ attribute=““>Celsius. This process can be easily scaled up,” he says.

Thermoelectric materials convert heat to electricity. This is especially useful in industrial processes where waste heat is reused as valuable electric power. The converse approach is the cooling of electronic parts, for example, in smartphones or cars. Materials used in these kinds of applications have to be not only efficient, but also inexpensive and, above all, safe for health.

However, thermoelectric devices used to date make use of expensive and toxic elements such as lead and tellurium, which offer the best conversion efficiency. To find safer alternatives, Emmanuel Guilmeau and his team have turned to derivatives of natural copper-based sulfide minerals. These mineral derivatives are mainly composed of nontoxic and abundant elements, and some of them have thermoelectric properties.

Now, the team has succeeded in producing a series of thermoelectric materials showing two crystal structures within the same material. “We were very surprised at the result. Usually, slightly changing the composition has little effect on the structure in this class of materials,” says Emmanuel Guilmeau describing their discovery.

The team found that replacing a small fraction of the manganese with copper produced complex microstructures with interconnected nanodomains, defects, and coherent interfaces, which affected the material’s transport properties for electrons and heat.

Emmanuel Guilmeau says that the novel material produced is stable up to 400 degrees Celsius (750 degrees Fahrenheit), a range well within the waste heat temperature range of most industries. He is convinced that, based on this discovery, novel cheaper, and nontoxic thermoelectric materials could be designed to replace more problematic materials.

Reference: “Engineering Transport Properties in Interconnected Enargite-Stannite Type Cu_2+xMn_1−xGeS₄ Nanocomposites” by Dr. V. Pavan Kumar, S. Passuti, Dr. B. Zhang, Dr. S. Fujii, K. Yoshizawa, Dr. P. Boullay, Dr. S. Le Tonquesse, Dr. C. Prestipino, Prof. B. Raveau, Prof. P. Lemoine, Dr. A. Paecklar, Dr. N. Barrier, Prof. X. Zhou, Prof. M. Yoshiya, Dr. K. Suekuni, Dr. E. Guilmeau, 13 September 2022, Angewandte Chemie International Edition.
DOI: 10.1002/anie.202210600

Funding: Agence Nationale de la Recherche, Horizon 2020 Framework Programme, Japan Society for the Promotion of Science