Enhanced thermoelectric performance of Mg3Sb2-based materials by codoping with B and Te

Abstract

n-Type Mg₃Sb₂ has been extensively studied in recent years as a potential near-room-temperature thermoelectric candidate to substitute commercial Bi₂Te₃. Among these studies, introducing external atoms through doping to improve thermoelectric performance is the mainstream method. This work focuses on the thermoelectric improvement of Mg_3.2SbBi by codoping with Te and B elements. As an effective n-type dopant, single doping with Te atoms increased the carrier concentration and conductivity, and Mg_3.2SbBi_0.97Te_0.03 achieved the highest power factor of ∼22.4 μW cm⁻¹ K⁻² at 623 K. The sum of the lattice and bipolar diffusion thermal conductivities (κ − κ_E) was as low as ∼0.53 W m⁻¹ K⁻¹ at 773 K due to the additional phonon scattering from the Te-substitutional defects. The x = 0.03 sample achieved the highest zT ∼ 1.52. Further, the addition of B element on Mg_3.2SbBi_0.97Te_0.03 led to a slightly inferior electronic performance, and the κ − κ_E of Mg_3.2B_0.03SbBi_0.97Te_0.03 decreased to 0.49 W m⁻¹ K⁻¹. As a result, the thermoelectric properties of Mg_3.2B_0.03SbBi_0.97Te_0.03 were slightly improved, and a peak zT of ∼1.54 at 623 K was achieved. Moreover, the Mg_3.2B_ySbBi_1−xTe_x prepared in this work by the ball-milling process exhibited excellent mechanical performance.