Bi₂Te₃-based thermoelectric materials are widely used in solid-state refrigeration near room temperature. However, the room temperature figure of merit (zT) of n-type Bi₂Te₃-based polycrystals produced by once sintering is always lower than 0.8. Herein, low-angle grain boundaries (LAGBs) are introduced in n-type Bi₂Te_2.7+xSe_0.3 by a simple step-hot-pressing procedure (once sintering) and well characterized by scanning transmission electron microscopy. LAGBs consist of dislocation arrays that can effectively scatter the medium-frequency phonons and thus suppress the lattice thermal conductivity. Although LAGBs also serve as scattering centers of low-energy electrons and deteriorate the carrier mobility, they could contribute to the enhanced Seebeck coefficient owing to the increased scattering factor. Overall, the samples with LAGBs own lower electronic thermal conductivity at the same power factor level. Finally, a high room temperature zT of 0.94 is obtained in n-type Bi₂Te_2.7Se_0.3, which is comparable to those produced by multiple-time sintering. Moreover, step-hot-pressing is also found to be effective in promoting the room temperature zT of p-type Bi₂Te₃-based polycrystals. This work puts forward a new and simple method to construct LAGBs in Bi₂Te₃-based alloys that enhances their zTs, and sheds light on the underlying mechanisms about how the LAGB affects the electrical and thermal transport properties.

Bi ₂ Te ₃基热电材料广泛应用于室温附近的固态制冷。然而，一次烧结制备的n型Bi ₂ Te ₃基多晶的室温品质因数( zT )始终低于0.8。在此，在n型 Bi ₂ Te _{2.7+ x} Se _0.3中引入了低角度晶界 (LAGB)通过简单的逐步热压程序（一次烧结）并通过扫描透射电子显微镜进行充分表征。LAGB 由位错阵列组成，可以有效地散射中频声子，从而抑制晶格热导率。尽管 LAGB 也可作为低能电子的散射中心并降低载流子迁移率，但由于散射因子增加，它们可能有助于提高塞贝克系数。总体而言，具有 LAGB 的样品在相同功率因数水平下具有较低的电子热导率。最后，在n型 Bi ₂ Te _2.7 Se _{0.3 中}获得了 0.94的高室温zT，这与多次烧结生产的产品相当。此外，步骤-热压也发现是有效地促进了室温的zT的p型的Bi ₂特₃系多晶。这项工作提出了一种在 Bi ₂ Te ₃基合金中构建 LAGB 的新方法，该方法可增强其zT，并阐明了有关 LAGB 如何影响电和热传输性能的潜在机制。