Multiple-valley effect on modulation of thermoelectric properties of n-type ZrCuSiAs-structure oxyantimonides LnTSbO (Ln= lanthanides and T=Zn, Mn)

Abstract Thermoelectric properties of n-type LnTSbO (Ln = lanthanides and T = Zn, Mn) were firstly investigated by the first-principles method and the semi-classical Boltzmann theory. The results show that a multiple-valley structure appears around the bottom of conduction band. The valley with a high band degeneracy consists of the bands with a weak band dispersion, leading to large magnitudes of the Seebeck coefficient but low electrical conductivity. The valley with a low band degeneracy is made up of the bands with an intense band dispersion, resulting in a high electrical conductivity but small magnitudes of the Seebeck coefficient. The thermoelectric properties are dominated by the energy difference, Δ E , between the valleys. The Δ E value of LnZnSbO linearly increases with the ionic radius of Ln. The thermoelectric properties are thus effectively modulated by varying the lanthanides. As a result, LnZnSbO (Ln = Ce-Nd) with the moderate values of Δ E shows a better thermoelectric performance. The multiple-valley effect is an effective way to modulate the thermoelectric properties of n-type LnTSbO.