Evaluating the Thermoelectric Properties of BaTiS by Density Functional Theory.

BaTiS is a semiconductor with a small bandgap of ∼0.5 eV and strong transport anisotropy caused primarily by structural anisotropy; it contains well-separated octahedral columns along the [0001] direction and low lattice thermal conductivity, appealing for thermoelectric applications. Here, we evaluate the prospect of BaTiS as a thermoelectric material by using the linearized electron and phonon Boltzmann transport theory based on the first-principles density functional band structure calculations. We find sizable values of the key thermoelectric parameters, such as the maximum power factor PF = 928 μW K and the maximum figure of merit ZT = 0.48 for an electron-doped sample and PF = 74 μW K and ZT = 0.17 for a hole-doped sample at room temperature, and a small doping level of ±0.25e per unit cell. The increase in temperature yields an increase in both the power factor and the figure of merit, reaching large values of PF = 3078 μW K and ZT = 0.77 for the electron-doped sample and PF = 650 μW K and ZT = 0.62 for the hole-doped sample at 800 K. Our results elucidate the promise of BaTiS as a material for the thermoelectric power generator.