Electronic and thermoelectric properties of the intermetallic compounds MNiSn (M=Ti, Zr, and Hf)

We have performed first-principles calculations for the half-Heusler type ternary compounds MNiSn (M=Ti, Zr, and Hf). To discuss the relationship between the electronic and thermoelectric properties, we evaluate Seebeck coefficients from the calculated band structure within the Boltzmann transport theory. The temperature and carrier concentration dependences of the Seebeck coefficients are discussed in terms of the density of states and Fermi velocity near the band edges. The calculated Seebeck coefficients for all these materials are found to be about -300 mu V/K at a low n-type carrier concentration at room temperature, being in good agreement with experiments.