Research of half-Heusler alloys gives insight into development of thermoelectric materials for high-temperature applications

The joint Russian-American paper makes advances in studying energy conversion efficiency, which is important for applications in ‘green’ tech.

Associate Professor Farit Vagizov (Kazan Federal University) contributed to the research with colleagues from Texas A&M University.

He comments, “Half-Heusler alloys are considered promising thermoelectric for applications above 1000 K.  The efficiency of a thermoelectric material depends on the thermoelectric figure of merit. The higher it is, the better the material. The figure of merit, in turn, depends on electrical and thermal conductivity. The higher the electrical conductivity and the lower the thermal conductivity, the better and more efficient the material is. Unfortunately, these two parameters are interrelated (if the electrical conductivity increases, so does the thermal conductivity), and it is not easy to achieve the optimal balance.”

To make that balance work, the team tried to test Nb_1−xTi_xFeSb by substituting niobium atoms with titanium atoms.

“We have obtained interesting data on the physics of thermoelectric properties in these new compounds. It turned out that these properties significantly depend on the nature of defects, the localization of resonance levels, and the electronic configuration of the constituent atoms. NMR and Mössbauer measurements on ⁹³Nb, ¹²¹Sb and ⁵⁷Fe nuclei allowed us to establish the features of the electronic configuration of the elements that make up the alloy, to reveal their contributions to the transport properties of the material. This knowledge can be used for a targeted search for thermoelectric materials with high values ​​of thermoelectric figure of merit in alloys such as a Heusler alloy,” explains Vagizov.

Such materials can be used to construct effective solar panels and thermoelectric generators. Thermoelectricity means not only transforming heat into electricity but also electricity into cooling.

 

Defect charging and resonant levels in half-Heusler Nb_1−xTi_xFeSb

https://www.sciencedirect.com/science/article/pii/S2542529320301024

 

Source text: Larisa Busil

Translation: Yury Nurmeev