Recent progress in Fe- and Ru-based full-Heusler bulk thermoelectrics

Full-Heusler compounds represent a rich and diverse class of functional materials, covering a large compositional phase space. Representatives with 24 valence electrons are commonly semimetals or narrow-gap semiconductors as per the Slater-Pauling rule and are thus considered as thermoelectric materials, especially for room-temperature applications. Research on the archetypal thermoelectric full-Heusler compound Fe₂VAl began over two decades ago, and since then, significant progress has been made in enhancing its thermoelectric performance. Advances have been achieved through various intrinsic and extrinsic substitutions, grain boundary engineering and other optimization strategies. Here, recent advancements are reviewed, challenges for the further development of competitive full-Heusler thermoelectrics are identified, and novel routes and concepts are highlighted that could make these materials viable for energy harvesting and cooling applications near room-temperature.