Significant reduction in the thermal conductivity of Si-substituted Fe2VAl epilayers

We experimentally find that the substitution of Si for Al in Heusler-type Fe-2 VA1 epilayers contributes to the significant reduction in the thermal conductivity, in which Fe-2 VA1 is one of the next-generation thermoelectric materials without using toxic elements. Because of the low-temperature growth of the epilayers, the Si substitution induces the decrease in the degree of L2(1) ordering, giving rise to the formation of V-Si antisite defects in the epilayers. For Fe-2 VA1(0.57)Si(0.43) epilayers, we can obtain a low thermal conductivity of similar to 3.9 W/(m K), one-third less than Si-substituted Fe-2 VA1 bulk samples [Lue et al., Phys. Rev. B 75, 064204 (2007)]. We discuss that a possible origin of the low thermal conductivity is related to the low lattice thermal conductivity due to the presence of the V-Si antisite defects.