New Non-Toxic and Inexpensive Synthetic Crystals can Convert Heat into Electricity

To effectively convert heat into electricity, scientists have created synthetic crystals made of sulfide minerals.

This novel substance, which is readily available from risk-free, non-toxic raw materials, opens up fresh possibilities for the creation of secure and reasonably priced so-called thermoelectric materials.

By making small changes to its composition, a synthetic copper mineral can develop a complex structure as well as a microstructure, setting the stage for the desired properties.

Novel Synthetic Crystals

Emmanuel Guilmeau, a materials scientist and CNRS researcher from the CRISMAT laboratory in Caen, France, explained that the novel synthetic material is made in a relatively straightforward process from copper, germanium, manganese, and sulfur.

Guilmeau is the corresponding author of the study.

He continued to say that to create a precrystallized phase, the powders are mechanically alloyed by ball milling, which is then densified at 600 degrees Celsius.

He pointed out that this procedure is simple to scale up.

Heat is converted into electricity by thermoelectric materials. This is particularly helpful in industrial processes where leftover heat is converted back into valuable electric power.

The opposite strategy is the cooling of electronic components, for instance in smartphones or automobiles.

These applications require materials that are not only effective but also affordable and, most importantly, health-safe.

Non-Toxic, Inexpensive Sources

The best conversion efficiency is provided by tellurium and lead, which are costly and hazardous materials used in thermoelectric devices.

Guilmeau and his team have looked to natural copper-based sulfide minerals as a source of safer substitutes.

Most of the elements in these mineral derivatives are nontoxic and abundant, and some of the materials have thermoelectric properties.

The team has now been successful in creating several thermoelectric materials that contain two crystal structures.

In describing their discovery, Guilmeau said that they were astonished by the outcome because, in this class of materials, a small change in composition typically has little impact on the structure.

The researchers discovered intricate microstructures with networked nanodomains, some defects, and coherent interfaces were produced when a small amount of the manganese was substituted with copper.

These microstructures had an impact on the material's heat and electron transport properties.

Thermoelectric Materials

According to the Smithells Metal Reference Book, the majority of thermoelectric materials are either solid solutions or compounds, and they are simple to synthesize using conventional solid-state methods.

The Bridgman method and liquid phase epitaxy are typical examples of common melt techniques, that include both stoichiometric and non-stoichiometric melts.

A compact powder is sintered at a high temperature in powder metallurgy, which is also frequently used.

PIES, or the pulverized and intermixed sintering method, and mechanical alloying are two additional synthetic methods that have been developed.

Molecular beam epitaxy, electrochemical deposition, and liquid phase epitaxy can all be used to create thin film structures.

Guilmeau says that the newly created material is stable up to 750 degrees Fahrenheit, which is well within the temperature range of waste heat for most industries.

Based on this discovery, he is confident that new, less expensive, and non-toxic thermoelectric materials could be developed to take the place of more problematic ones, Sci Tech Daily reported.

The findings of Guilmeau's study, which was funded by the Agence Nationale de la Recherche, the Japan Society for the Promotion of Science, and the Horizon 2020 Framework Programme, were published recently in the journal Angewandte Chemie.