Enhanced phonon scattering by mass and strain field fluctuations in Nb substituted FeVSb half-Heusler thermoelectric materials

The substitution of V by Nb in FeV1−xNbxSb (x = 0, 0.1, 0.2, 0.3, and 0.4) half-Heusler thermoelectric materials was introduced to lower the lattice thermal conductivity by the alloy scattering. A significantly reduced thermal conductivity of ∼5.5 W m−1 K−1 for the FeV0.6Nb0.4Sb was obtained at room temperature, a decrease of ∼55% compared with that of FeVSb. The disorder scattering parameters of mass fluctuation Γm and strain field fluctuation Γs were calculated to explore the dominant factors for the enhanced phonon scattering. The obtained Γm was comparable to the Γs. Therefore, the reduction of thermal conductivity in Nb substituted FeVSb compounds was attributed to both the mass and the strain field fluctuations.