Effect of Off-Stoichiometry and Point Defects on Thermoelectric Properties of a W-Substituted Fe₂VAl Heusler Compound

Fe2VAl-based Heusler thermoelectric materialsare attractivefor power supplies used in practical applications to drive Internetof things (IoT) devices using low-temperature waste heat at temperaturesof less than 500 K. In this paper, we present a simple method to introducepoint defects and disorder at Fe/V sites via W substitutionto enhance the thermoelectric performance of Fe2-x W x VAl (x = 0, 0.05, 0.1, and 0.15) samples. We obtained a relatively highdimensionless figure of merit zT of 0.28 at 423 Kfor the samples with x = 0.05 and 0.1. Although bothsamples had the same maximum zT value, the samplewith x = 0.05 showed a power factor of 4.7 mW m(-1) K-2 at 423 K, which was higherthan that (3.7 mW m(-1) K-2 at 423K) of the sample with x = 0.1. In addition, the thermalconductivity of 7.1 W m(-1) K-1 at423 K of the sample with x = 0.05 was higher thanthat (5.7 W m(-1) K-1 at 423 K)of the sample with x = 0.1. We confirmed that thesynthesized sample with x = 0.05 showed excellentthermal durability that allowed it to maintain almost constant electricalresistivity and Seebeck coefficient for 10,000 min; this was confirmedby exposure tests performed at 423 and 573 K. The current simple fabricationprocess, which uses a combination of melting and sintering methods,will be attractive for mass production of the W-substitutedFe(2)VAl-based Heusler compound with the relatively high zT of 0.28.