Garmroudi’s research stay

The Lions Scholarship enabled Fabian Garmroudi to finance a one-month research stay at the National Institute for Materials Science, one of the largest research facilities in Japan, which is located in Tsukuba, Ibaraki prefecture. The awardee visited the laboratory of Prof. Mori, one of the worldwide leading experts in the field of thermoelectrics, who has already worked closely with the researchers from TU Wien before.

During his research stay Garmroudi investigated the thermoelectric properties of so-called Heusler alloys based on the elements Iron, Vanadium and Aluminum (Fe₂VAl). Here, the goal was to increase the thermoelectric performance, more specifically the so-called zT value, which determines the conversion efficiency of thermoelectric devices. Heusler alloys might be attractive for various technological applications such as waste heat harvesting or cooling in the temperature range from room temperature to around 100 °C. To achieve this, however, it is crucial to increase the zT value. In order to achieve high zT values, a large Seebeck coefficient, a large electrical conductivity, but a small thermal conductivity have to be realized within the same material. This is no easy task as all these physical properties are tightly coupled and interrelated. “Trying to optimize one parameter almost always deteriorates the others”, explains Fabian Garmroudi the multidimensional optimization problem in thermoelectric materials.

The state-of-the-art material bismuth telluride (Bi₂Te₃) had been discovered already back in the 1950s and is nowadays commercially available. While Bi₂Te₃-based systems are still substantially more efficient featuring zT values three times larger than those of Fe₂VAl-based Heusler alloys, the latter have certain advantages such as the low abundance and cost efficiency of their constituents as well as excellent mechanical properties. During his research stay Garmroudi aimed to tailor the micro- and nanostructure of Fe₂VAl-based Heusler alloys in order to reduce their comparably large lattice thermal conductivity without deteriorating the electronic transport. “Owing to excellent equipment and collaboration with members of the Mori group, we were able to achieve promising achievements with respect to the thermoelectric performance. Moreover, I was able to meet many new people and make some friends along the way”, says Garmroudi.

The young scientist plans on publishing his results, that have been obtained with the financial help of the Lions Scholarship, in high-impact journals in the near future.