Thermoelectric properties of Heusler-type Ru2VAl1−xGax alloys.

Electrical and thermal transport properties of the Heusler-type alloys, Ru 2 VAl 1− x Ga x ( x = 0.0–1.0) were studied by means of the electrical resistivity, Seebeck coefficient, and thermal conductivity measurements. All studied compounds show weak metallic characteristics with a low residual resistivity ratio. In addition, the Ru 2 VAl 1− x Ga x alloys with x ≤ 0.75 show an n -type thermoelectric conduction from 10 to 300 K, while Ru 2 VGa displays p -type conduction. The estimated Fermi energy of these materials is higher than 0.5 eV, endorsing their metallic character. From the thermal conductivity study, we noticed that low-temperature thermal conductivity decreases with increasing Ga content for x ≤ 0.5 and then increases with further Ga substitution. This observation is essentially due to the change in the phonon scattering processes as a result of the substitution of heavier Ga atoms into the Al sites of Ru 2 VAl. It is important that an enhanced thermoelectric figure of merit ZT was found in Ru 2 VAl 0.25 Ga 0.75 , about seven times higher than that in Ru 2 VAl. [ABSTRACT FROM AUTHOR]