Du Xiaolong, Hu Ping, Mao Tao, Song Qingfeng, Qiu Pengfei, Shi Xun, Chen Lidong
State Key Laboratory of High Performance Ceramics and Superfine Microstructure , Shanghai Institute of Ceramics, Chinese Academy of Sciences , Shanghai 200050 , China.
Center of Materials Science and Optoelectronics Engineering , University of Chinese Academy of Sciences , Beijing 100049 , China.
ACS Appl Mater Interfaces. 2019 Sep 4;11(35):32151-32158. doi: 10.1021/acsami.9b10648. Epub 2019 Aug 22.
β-FeSi has been considered a promising material for thermoelectric applications, but its thermoelectric performance is greatly limited by the overhigh lattice thermal conductivity. In thermoelectrics, alloying an effective method to reduce the lattice thermal conductivity. In this study, we chose the Co-doped β-FeSi (FeCoSi) as the matrix and then prepared a series of Ru alloyed FeRuCoSi ( = 0, 0.005, 0.01, 0.02, and 0.05). X-ray characterizations show that all samples crystallize in the β-FeSi structure. The elemental mappings detect an inhomogeneous Ru distribution in FeRuCoSi, which is attributed to the different Ru solution contents in ε-FeSi and α-FeSi before the formation of β-FeSi and the slow diffusion behavior of Ru during the annealing process. The Ru-alloying obviously reduces the lattice thermal conductivity via introducing the mass and strain field fluctuations to interrupt the phonon transports, while it has a weak effect on electrical transport properties. Finally, a maximum value of 0.33 at 900 K has been obtained for FeRuCoSi, which is about 27% higher than that for FeCoSi.
β-FeSi一直被认为是热电应用的一种有前景的材料，但其热电性能受到过高晶格热导率的极大限制。在热电学中，合金化是降低晶格热导率的一种有效方法。在本研究中，我们选择Co掺杂的β-FeSi（FeCoSi）作为基体，然后制备了一系列Ru合金化的FeRuCoSi（x = 0、0.005、0.01、0.02和0.05）。X射线表征表明所有样品均结晶为β-FeSi结构。元素映射检测到FeRuCoSi中Ru分布不均匀，这归因于在β-FeSi形成之前ε-FeSi和α-FeSi中不同的Ru固溶体含量以及退火过程中Ru的缓慢扩散行为。Ru合金化通过引入质量和应变场波动来中断声子输运，从而明显降低了晶格热导率，而对电输运性质的影响较弱。最终，FeRuCoSi在900 K时获得了0.33的最大zT值，比FeCoSi高出约27%。
