Electronic structure and thermoelectric properties of full Heusler compounds Ca(2)YZ (Y = Au, Hg; Z = As, Sb, Bi, Sn and Pb)

We investigate the transport properties of bulk Ca(2)YZ (Y = Au, Hg; Z = As, Sb, Bi, Sn and Pb) by a combination method of first-principles and Boltzmann transport theory. The focus of this article is the systematic study of the thermoelectric properties under the effect of a spin–orbit coupling. The highest dimensionless figure of merit (ZT) of Ca(2)AuAs at optimum carrier concentration are 1.23 at 700 K. Interestingly enough, for n-type Ca(2)HgPb, the maximum ZT are close to each other from 500 K to 900 K and these values are close to 1, which suggests that semimetallic material can also be used as an excellent candidate for thermoelectric materials. From another viewpoint, at room temperature, the maximum PF for Ca(2)YZ are greater than 3 mW m(−1) K(−2), which is very close to that of ∼3 mW m(−1) K(−2) for Bi(2)Te(3) and ∼4 mW m(−1) K(−2) for Fe(2)VAl. However, the room temperature theoretical κ(l) of Ca(2)YZ is only about 0.85–1.6 W m(−1) K(−1), which is comparing to 1.4 W m(−1) K(−1) for Bi(2)Te(3) and remarkably lower than 28 W m(−1) K(−1) for Fe(2)VAl at same temperature. So Ca(2)YZ should be a new type of promising thermoelectric material at room temperature.