Large improvement in thermoelectric performance of pressure-tuned Mg(3)Sb(2)

The Mg(3)Sb(2)-based Zintl compound is a promising candidate for a high-performance thermoelectric material with the advantage of the component elements being low cost, non-toxic and earth-abundant. Here, we investigate the influence of pressure on the electronic structure and p-type and n-type thermoelectric transport properties of Mg(3)Sb(2) by using density functional theory and Boltzmann transport theory. The energy gaps first increase and then decrease with the increasing of pressure, and a peak value of the valley degeneracy of conduction band occurs at 4 GPa. Based on the calculated band structures, the zT (figure of merit) values of p-type Mg(3)Sb(2) under pressure are significantly enhanced, which predominantly originates from the boosted PF (power factor) contributed by the increased carrier's relaxation time. When the carrier concentration reaches 1 × 10(20) cm(−3), the PF of p-type Mg(3)Sb(2) at 4 GPa is increased by 35% relative to that of the compound at 0 GPa, thus leading to a considerably improved zT of ∼0.62 at 725 K. Under the same conditions, due to the increased density of states effective mass, the n-type Mg(3)Sb(2) exhibits a highest PF of ∼19 μW cm(−1) K(−2) and a peak zT of 1.7. Therefore, pressure tuning is an effective method to improve the p-type and n-type thermoelectric transport performance of Mg(3)Sb(2)-based Zintl compounds. This work on Mg(3)Sb(2) under pressure may provide a new mechanism for the experimenters towards the enhancement of the thermoelectric performance of materials.