Nanoscale heterogeneity in thermoelectrics: the occurrence of a phase separation in Fe-doped Ca3Co4O9
Nanoscale heterogeneity in thermoelectrics: the occurrence of a phase separation in Fe-doped Ca3Co4O9
复制标题
热电学中的纳米级异质性：Fe 掺杂 Ca3Co4O9 中相分离的发生
DOI：
10.1039/c6cp00819d
复制
发表时间：
2016
期刊：
影响因子：
--
通讯作者：
Ce-Wen Nan
中科院分区：
文献类型：
--
作者：
Wei Xu;Sajid Butt;Yingcai Zhu;Jing Zhou;Yong Liu;Meijuan Yu;Augusto Marcelli;JinLe Lan;Yuan-Hua Lin;Ce-Wen Nan
失配层状钴酸盐热电材料是高温热电应用的良好候选材料。Ca3Co4O9是该家族的典型化合物，由岩盐Ca2CoO3板与沿b轴晶格失配较大的六边形CoO2板交替组成。每块板的厚度为0.3-0.5 nm，在纳米尺度上表现出固有的结构不均匀性。后者是影响这些失配结构热电体中电输运和热流的关键参数。为了阐明铁掺杂Ca3Co4O9热电性能的物理根源，我们将x射线近边吸收光谱（XANES）和密度泛函理论的量子建模相结合。与单位点掺杂相比，低掺杂时，铁掺杂首先发生在岩盐板的Co1位点，而高掺杂时，铁掺杂更倾向于岩盐板的Ca1位点。Ca1位点的掺杂改变了电子结构，调整了纳米级结构的非均质性。该机理为优化失配层状热电材料的热电性能开辟了一条新的途径。
The misfit layered cobaltate thermoelectrics are good candidates for high temperature thermoelectric applications. Ca3Co4O9 is a typical compound of this family, which consists of rock salt Ca2CoO3 slabs alternating with hexagonal CoO2 slabs with a large lattice mismatch along the b axis. Each slab is 0.3–0.5 nm thick and shows an inherent structural heterogeneity at the nanoscale. The latter is a key parameter that affects the electrical transport and the heat flow in these misfit structured thermoelectrics. To clarify the physical origin of the thermoelectric performance of iron doped Ca3Co4O9 we combined X-ray near-edge absorption spectroscopy (XANES) and quantum modeling using density functional theory. In contrast to single-site doping, the iron doping first occurs at the Co1 site of the rock salt slab at low doping while at higher doping it prefers the Ca1 site of the rock salt slab. Doping at the Ca1 site modifies the electronic structure tuning the nanoscale structural heterogeneity. This mechanism may open a new route to optimizing the thermoelectric performance of misfit layered thermoelectrics.