Thermoelectric properties of Heusler-type Ru2VAl1−xGax alloys

Electrical and thermal transport properties of the Heusler-type alloys, Ru2VAl1−xGax (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 Ru2VAl1−xGax alloys with x ≤ 0.75 show an n-type thermoelectric conduction from 10 to 300 K, while Ru2VGa 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 Ru2VAl. It is important that an enhanced thermoelectric figure of merit ZT was found in Ru2VAl0.25Ga0.75, about seven times higher than that in Ru2VAl.