A synthetic sulfide mineral with thermoelectric properties.
In the effort to efficiently convert heat into electricity, easily accessible materials from harmless raw materials open new perspectives in the development of safe and cheap so-called thermoelectric materials. A synthetic copper mineral acquires complex structure and microstructure through simple changes in its composition, thus laying the foundation for desired properties, according to a study recently published in the journal Angewandte Chemie. The new synthetic material consists of copper, manganese, germanium and sulfur and is produced by a rather simple process, explains material scientist Emmanuel Guilmeau, a CNRS researcher at the CRISMAT laboratory, Caen, France, who is the corresponding author of the study. . “The powders are simply mechanically alloyed by ball milling to form a pre-crystallized phase, which is then condensed at 600 degrees Celsius. This process can easily be scaled up,” he says. Thermoelectric materials convert heat into electricity. This is particularly useful in industrial processes where waste heat is reused as valuable electricity. The reverse approach is to cool electronic components, for example, in smartphones or cars. The materials used in such applications must be not only effective, but also cheap and, above all, safe for health. However, the thermoelectric devices used to date use 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 copper-based derivatives of natural sulfide minerals. These mineral derivatives are mainly composed of non-toxic and abundant elements, and some of them have thermoelectric properties. Now, the team has succeeded in producing a series of thermoelectric materials that show two crystal structures within the same material. “We were very surprised by the result. Usually, slightly changing the composition has little effect on the structure of this class of materials,” says Emmanuel Guilmeau describing their discovery. The team found that replacing a small fraction of manganese with copper produced complex microstructures with interconnected nanodomains, defects and cohesive interfaces, which affected the material’s electron and heat transport properties. Emmanuel Guilmeau says the new material produced is stable up to 400 degrees Celsius (750 degrees Fahrenheit), a range that is within the waste heat temperature range of most industries. He is convinced that, based on this discovery, new cheaper and non-toxic thermoelectric materials could be designed to replace more problematic materials. Citation: “Mechanical Transport Properties in Interlinked Enargite-Stannite Type Cu2+XMn1−XGeS4 Nanocomposites” by Dr. V. Pavan Kumar, S. Passuti, Dr. B. Zhang, Dr. S. Fujii, K. Yoshizawa, and Drs. P. Boulllay, Dr. S. Le Tonquesse, Dr. C. Prestipino, Prof. B. Raveau, Prof. P. Lemoine, Dr. A. Paecklar, Dr. N. Barrier, Prof. X. Zhou, Prof. M. Josiah, Dr. K. Suekuni, Dr. E. Guilmeau, Applied Chemistry International Edition.DOI: 10.1002/anie.202210600 Funding: Agence Nationale de la Recherche, Horizon 2020 Framework Programme, Japan Society for the Promotion of Science
