Zhou Chongjian, Lee Yong Kyu, Cha Joonil, Yoo Byeongjun, Cho Sung-Pyo, Hyeon Taeghwan, Chung In
Center for Nanoparticle Research , Institute for Basic Science (IBS) , Seoul 08826 , Republic of Korea.
J Am Chem Soc. 2018 Jul 25;140(29):9282-9290. doi: 10.1021/jacs.8b05741. Epub 2018 Jul 11.
Introducing structural defects such as vacancies, nanoprecipitates, and dislocations is a proven means of reducing lattice thermal conductivity. However, these defects tend to be detrimental to carrier mobility. Consequently, the overall effects for enhancing ZT are often compromised. Indeed, developing strategies allowing for strong phonon scattering and high carrier mobility at the same time is a prime task in thermoelectrics. Here we present a high-performance thermoelectric system of Pb(Sb□)SeTe (□ = vacancy; y = 0-0.4) embedded with unique defect architecture. Given the mean free paths of phonons and electrons, we rationally integrate multiple defects that involve point defects, vacancy-driven dense dislocations, and Te-induced nanoprecipitates with different sizes and mass fluctuations. They collectively scatter thermal phonons in a wide range of frequencies to give lattice thermal conductivity of ∼0.4 W m K, which approaches to the amorphous limit. Remarkably, Te alloying increases a density of nanoprecipitates that affect mobility negligibly and impede phonons significantly, and it also decreases a density of dislocations that scatter both electrons and phonons heavily. As y is increased to 0.4, electron mobility is enhanced and lattice thermal conductivity is decreased simultaneously. As a result, Pb(Sb□)SeTe exhibits the highest ZT ∼ 1.5 at 823 K, which is attributed to the markedly enhanced power factor and reduced lattice thermal conductivity, in comparison with a ZT ∼ 0.9 for Pb(Sb□)Se that contains heavy dislocations only. These results highlight the potential of defect engineering to modulate electrical and thermal transport properties independently. We also reveal the defect formation mechanisms for dislocations and nanoprecipitates embedded in Pb(Sb□)SeTe by atomic resolution spherical aberration-corrected scanning transmission electron microscopy.
引入诸如空位、纳米沉淀和位错等结构缺陷是降低晶格热导率的一种行之有效的方法。然而，这些缺陷往往对载流子迁移率有害。因此，增强ZT的总体效果常常受到影响。实际上，开发同时实现强声子散射和高载流子迁移率的策略是热电学中的首要任务。在此，我们展示了一种嵌入独特缺陷结构的高性能Pb(Sb□)SeTe（□ = 空位；y = 0 - 0.4）热电系统。考虑到声子和电子的平均自由程，我们合理地整合了多种缺陷，包括点缺陷、空位驱动的密集位错以及由Te诱导的具有不同尺寸和质量涨落的纳米沉淀。它们共同在很宽的频率范围内散射热声子，使晶格热导率达到约0.4 W m⁻¹ K⁻¹，接近非晶态极限。值得注意的是，Te合金化增加了纳米沉淀的密度，其对迁移率的影响可忽略不计，但能显著阻碍声子，同时它还降低了严重散射电子和声子的位错密度。随着y增加到0.4，电子迁移率增强，同时晶格热导率降低。结果，Pb(Sb□)SeTe在823 K时表现出最高的ZT约为1.5，这归因于功率因子的显著增强和晶格热导率的降低，相比之下，仅含有重位错的Pb(Sb□)Se的ZT约为0.9。这些结果突出了缺陷工程独立调节电输运和热输运性质的潜力。我们还通过原子分辨率球差校正扫描透射电子显微镜揭示了嵌入Pb(Sb□)SeTe中的位错和纳米沉淀的缺陷形成机制。
