Thermoelectric devices require thermoelectric materials with high figure-of-merit (ZT) values in the operating temperature range. In recent years, the Zintl phase compound, n-Mg₃Sb₂, has received much attention owing to its rich chemistry and structural complexity. However, it hardly achieves high ZT values throughout the medium temperature range. Herein, by increasing the sintering temperature as much as possible, we successfully increased the average grain size of the compound by 15 times, and the grain boundary scattering was manipulated to obtain high carrier mobility of up to 180 cm² V⁻¹ s⁻¹. Simultaneously, we optimized the Mg content for ultralow lattice thermal conductivity. We first doped the Mg₃Sb₂-based materials with boron for higher sintering temperature, good thermal stability, and higher hardness. The synergistic optimization of electrical and thermal transport resulted in excellent ZT values (0.62 at 300 K, 1.81 at 773 K) and an average ZT of 1.4 (from 300 to 773 K), which are higher than the state-of-the-art values for n-type thermoelectric materials, demonstrating a high potential in device applications.

热电设备需要在工作温度范围内具有高品质因数（ZT）值的热电材料。近年来，Zintl相化合物n-Mg ₃ Sb ₂由于其丰富的化学性质和结构复杂性而受到广泛关注。但是，在整个中等温度范围内几乎都无法实现高ZT值。在此，通过尽可能提高烧结温度，我们成功地将化合物的平均晶粒尺寸增加了15倍，并且对晶界散射进行了控制，从而获得了高达180 cm ² V ^-1 s ^-1的高载流子迁移率。同时，我们优化了Mg的含量以实现超低晶格热导率。我们首先用硼掺杂Mg ₃ Sb ₂基材料，以获得更高的烧结温度，良好的热稳定性和更高的硬度。电气和热传输的协同优化产生了出色的ZT值（300 K时为0.62，773 K时为1.81），平均ZT为1.4（从300到773 K），这比最新技术要高n型热电材料的阻值，表明在器件应用中具有很高的潜力。