Previous thermoelectric devices use expensive and toxic elements. Now scientists have created inexpensive crystals composed of copper, manganese, germanium, and sulfur that can efficiently convert heat to electricity.
A synthetic sulfide mineral with thermoelectric properties.
In the effort to efficiently convert heat into electricity, easily accessible materials from harmless raw materials open up new perspectives in the development of safe and inexpensive 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 the desired properties, according to a study published recently in the journal Angewandte Chemie.
The novel synthetic material is composed of copper, manganese, germanium, and sulfur, and it is produced in a rather 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 precrystallized phase, which is then densified by 600 degrees CelsiusThe Celsius scale, also known as the centigrade scale, is a temperature scale named after the Swedish astronomer Anders Celsius. In the Celsius scale, 0 °C is the freezing point of water and 100 °C is the boiling point of water at 1 atm pressure.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>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 FahrenheitThe Fahrenheit scale is a temperature scale, named after the German physicist Daniel Gabriel Fahrenheit and based on one he proposed in 1724. In the Fahrenheit temperature scale, the freezing point of water freezes is 32 °F and water boils at 212 °F, a 180 °F separation, as defined at sea level and standard atmospheric pressure. ” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>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 Cu2+xMn1−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
Source: SciTechDaily
