Electronic and thermoelectric properties of ZrSxSe2−x

Abstract

The electronic, phonon, and transport properties of ternary ZrSxSe2−x (x = 0, 1, and 2) have been calculated based on density functional theory (DFT), density functional perturbation theory (DFPT), and Boltzmann transport theory. Two methods for engineering of the electronic and transport properties of ternary ZrSxSe2−x (x = 0, 1, and 2) shall be treated: (i) doping which can be achieved by the help of the rigid band approximation could be valid for the low doping levels of n- and p-type of ZrSxSe2−x (x = 0.1, 2). (ii) The substitution of S by Se in ZrSxSe2−x (x = 0.1, 2). Here, both methods have been applied to engineer the bandgap and power factor. This enables us to look at the optimal power factor and figure of merit for the n- and p-type doped ternary ZrSxSe2−x (x = 0, 1, and 2). It has been found that the p- doped ZrSe2 has the highest power factor and the lowest bandgap between three compounds while the highest Seebeck coefficient is observed in ZrS2. But the highest figure of merit (ZT) is found in ZrSeS which has the lowest lattice thermal conductivity such that at 300 K it is about 0.33 and 0.32 for the n- and p-doped, respectively. The minimum total thermal conductivity has also been obtained in ZrSeS which is 0.61 and 0.18 along the a- and c-directions, respectively at 1000 K. This value of the lattice thermal conductivity along the c-axis is even lower than the reported value for the well-known low lattice thermal conductivity of SnSe [L.D. Zhao, et al. Nature, 508, 373 (2014)].