Ternary PbBi₂S₄ compound with crustal S-rich element and low lattice thermal conductivity is considered as a potential thermoelectric candidate. However, its inferior thermoelectric properties are rooted in the low electrical transport performance. Generally, enhancing electrical transport performance (power factor, PF) primarily entails optimizing the interdependent relationship between carrier mobility μ (linked to electrical conductivity σ) and effective mass m* (related to Seebeck coefficient S). In this work, we introduce the strategy of alloy scattering to independently enhance S without weakening μ and simultaneously reduce thermal conductivity, leading to a synergetic optimization of electron and phonon in PbBi₂S₄ thermoelectric. Heavy Sn alloying in PbBi₂S₄ presents uniform and orderly distribution on Pb sites as unclosed by the atomic-scale crystal structure observation. These massive Sn atom serves as scattering centers and turns the electron scattering mechanism to be dominated by alloy scattering, thus resulting in a ∼ 33% increment of S in Pb_0.6Sn_0.4Bi₂S₄. Meanwhile, Sn alloying aggravates phonon scattering further lowering lattice thermal conductivity and reaching an extremely low value of 0.34 W·m^–1·K^–1 at 773 K. Finally, a maximum zT of 0.68 at 773 K is obtained in Pb_0.6Sn_0.4Bi₂S₄, which is ∼ 45% higher than the pristine matrix. This study proves that the strategy of alloy scattering is effective in improving overall electrical transport properties as well as reducing lattice thermal conductivity, which paves a new way to develop high-performance thermoelectric materials.

中文翻译：

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合金散射以优化 PbBi2S4 热电中的载流子和声子传输性能


具有地壳富 S 元素和低晶格热导率的三元 PbBi₂S₄ 化合物被认为是潜在的热电候选者。然而，其较差的热电性能源于低电传输性能。通常，提高电传输性能（功率因数，PF）主要需要优化载流子迁移率 μ（与电导率 σ 有关）和有效质量 m*（与塞贝克系数 S 有关）之间的相互依存关系。在这项工作中，我们引入了合金散射策略，在不削弱 S 的情况下独立增强 S μ同时降低热导率，从而在 PbBi₂S₄ 热电中实现电子和声子的协同优化。PbBi₂S₄ 中的重 Sn 合金在 Pb 位点上呈现均匀有序的分布，而原子尺度晶体结构观察未闭合。这些大质量 Sn 原子充当散射中心，使电子散射机制以合金散射为主，从而导致 Pb_0.6Sn_0.4Bi₂S₄ 中的 S 增加 ∼ 33%。同时，Sn 合金化加剧了声子散射，进一步降低了晶格热导率，并达到了 0.34 W·m^–1·^K-1 在 773 K 时。最后，在 Pb_{0.6 Sn 0.4}Bi₂S₄ 中获得 773 K 时的最大 zT 为_0.68，比原始基质高 ∼ 45%。 本研究证明，合金散射策略可有效改善整体电传输性能以及降低晶格热导率，为开发高性能热电材料铺平了一条新路。