Científicos crean cristales que generan electricidad a partir del calor

Un mineral de sulfuro sintético con propiedades termoeléctricas.

En un esfuerzo por convertir eficientemente el calor en electricidad, los materiales de fácil acceso a partir de materias primas inocuas abren nuevas perspectivas en el desarrollo de los llamados materiales termoeléctricos seguros y rentables. Un mineral de cobre sintético adquiere una estructura y microestructura complejas a través de simples cambios en su composición, preparando así el escenario para las propiedades deseadas, según un estudio publicado recientemente en la revista Angewandte Chemie.

El nuevo material sintético está compuesto de cobre, manganeso, germanio y azufre y se produce en un proceso bastante simple, explica el científico de materiales Emmanuel Guilmeau, investigador del CNRS en el laboratorio CRISMAT, Caen, Francia, quien es el autor correspondiente del estudio. «Los polvos simplemente se unen mecánicamente mediante molienda de bolas para formar una fase precristalizada, que luego se densifica a 600 grados.[{» 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