Team makes crystals that generate electricity from heat

To convert heat into electricity, easily accessible materials from harmless raw materials open up new perspectives in the development of safe and cheap so-called “thermoelectric materials”. A synthetic copper mineral acquires a complex structure and microstructure through simple changes in its composition, thereby laying the foundation for its desired properties, according to a study published in the journal applied chemistry.

The new synthetic material is composed of copper, manganese, germanium and sulfur and is produced in a fairly simple process, explains materials scientist Emmanuel Guilmeau, CNRS researcher at 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 densified to 600 degrees Celsius. This process can be easily scaled up,” he says.

Thermoelectric materials convert heat into electricity. This is especially useful for industrial processes Where waste heat is reused as valuable electrical energy. The reverse approach is the cooling of electronic components, for example in smartphones or cars. Materials used in these types of applications must not only be efficient, but also cheap and above all safe for health.

However, thermoelectric devices hitherto use expensive and toxic elements such as lead and tellurium, which provide the best conversion efficiency. To find safer alternatives, Emmanuel Guilmeau and his team turned to derivatives of natural copper-based 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 managed a series thermoelectric materials shows two crystal structures in the same material. “We were very surprised by the result. Usually a small change in 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 portion 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 new material produced is stable up to 400 degrees Celsius, a range well within the waste heat temperature range of most industries. He is convinced that based on this discovery, cheaper, new and non-toxic thermoelectric materials can be designed to replace more problematic materials.