A silicon wafer coated with a thin film of the high-entropy alloy in the ETH researchers’ laboratory. (Photo: Fabio Bergamin / ETH Zurich)

The ETH researchers’ material is remarkable not only for its extremely intricate pillar structure but also for its internal crystal structure. Like most crystalline bodies, this material also consists of a large number of small individual crystals. The special feature of the alloy is that these individual crystals are tiny – in scientific terms, this is referred to as a nanocrystalline material. “Although nanocrystalline materials have many desirable properties, they often also bring disadvantages,” explains Yu Zou, a doctoral student in Spolenak’s group and first author of the study, which has now been published in the journal Nature Communications. “For example, these materials are usually not temperature-resistant, as heating causes the individual crystals to expand and therefore changes the properties of the material.”

According to the scientists, the high-entropy alloy’s ability to withstand extreme temperatures may be related to the relatively disordered atomic distribution of the elements inside the material. In particular, the researchers suspect that the disorder at the internal boundary surfaces of individual crystals in high-entropy alloys means the crystals tend to grow less than in other materials when heated. Whether this theory is accurate is something the scientists wish to investigate in another research project, in which they will scrutinise the atomic distribution of elements within the material.

Zou says the new material will be of interest above all in high-pressure and high-temperature applications, for example for building sensors that are required to operate in extreme conditions of this kind.