Discovery of triple half-Heusler Mg2VNi3Sb3 with low thermal conductivity

To expand and utilize the potential of intermetallic compounds, the importance of quaternary half-Heusler (HH) compounds has attracted attention in the field of thermoelectrics and other inorganic materials research. In this study, triple half-Heusler (THH) Mg2VNi3Sb3 was successfully synthesized by following an unconventional valence balance strategy. X-ray diffraction (XRD) and scanning electron microscope energy dispersive spectroscopy (SEM-EDS) showed the pure and homogeneous nature of samples. Even though both ternary components of Mg2VNi3Sb3, i.e., MgNiSb and VNiSb are expected to be unstable with the metallic transport properties, Mg2VNi3Sb3 possesses semiconducting behavior with Seebeck coefficient peak larger than 115 mu V K-1 around 500 K with the small bandgap of 0.12 eV. The lattice thermal conductivity (kappa(L) = 2.0 W m(-1) K-1) of Mg2VNi3Sb3 is much smaller than kappa(L) of conventional half-Heusler and double half-Heusler materials. Since high thermal conductivity has been always a problem for HH materials, the synthesis of THH with low lattice thermal conductivity can be a new direction for developing high-performance HH compounds. Through the synthesis of THH Mg2VNi3Sb3, a new strategy to explore the huge compositional space for further improvement of thermoelectric performance and extended tunability of intermetallic compounds was demonstrated.