On Intensifying Carrier Impurity Scattering to Enhance Thermoelectric Performance in Cr‐Doped CeyCo4Sb12
On Intensifying Carrier Impurity Scattering to Enhance Thermoelectric Performance in Cr‐Doped CeyCo4Sb12
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DOI：
10.1002/adfm.201502782
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发表时间：
2015-11
影响因子：
19
通讯作者：
Shanyu Wang;Jiong Yang;Lihua Wu;Ping Wei;Wenqing Zhang;Jihui Yang
中科院分区：
文献类型：
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作者：
Shanyu Wang;Jiong Yang;Lihua Wu;Ping Wei;Wenqing Zhang;Jihui Yang
杂质散射对热电性能的有益影响长期以来一直被忽视，即使在半个多世纪前Ioffe已经提出了功率因数的可能改进。本文从理论和实验上证明了适当增强电离杂质对载流子的散射可以通过提高塞贝克系数和降低电子热导率来提高热电优值（ZT）。获得最大ZT的最佳电离杂质散射强度取决于费米能级和态密度有效质量。CeyCo4Sb12中的Cr掺杂逐渐增加了电离杂质散射的强度，并显着提高了塞贝克系数，导致45 μW cm−1 K−2的高功率因数和相对较低的电导率。这种效应，结合增加的Ce填充分数以及由此通过Cr掺杂剂的电荷补偿而降低的晶格热导率，在800 K下产生1.3的最大ZT，并且在500和850 K之间产生1.1的大的平均ZT，与不含Cr的样品相比，分别提高了约30%和约20%。此外，本研究还揭示了载流子散射参数可以作为优化热电材料电性能和提高热电转换效率的另一个基本自由度。
The beneficial effect of impurity scattering on thermoelectric properties has long been disregarded even though possible improvements in power factor have been suggested by Ioffe more than a half century ago. Here it is theoretically and experimentally demonstrated that proper intensification of ionized impurity scattering to charge carriers can benefit the thermoelectric figure of merit (ZT) by increasing the Seebeck coefficient and decreasing the electronic thermal conductivity. The optimal strength of ionized impurity scattering for maximum ZT depends on the Fermi level and the density of states effective mass. Cr‐doping in CeyCo4Sb12 progressively increases the strength of ionized impurity scattering, and significantly improves the Seebeck coefficient, resulting in high power factors of 45 μW cm−1 K−2 with relatively low electrical conductivity. This effect, combined with the increased Ce‐filling fraction and thus decreased lattice thermal conductivity by charge compensation of Cr‐dopant, gives rise to a maximum ZT of 1.3 at 800 K and a large average ZT of 1.1 between 500 and 850 K, ≈30% and ≈20% enhancements as compared with those of Cr‐free sample, respectively. Furthermore, this study also reveals that carrier scattering parameter can be another fundamental degree of freedom to optimize electrical properties and improve thermal‐to‐electricity conversion efficiencies of thermoelectric materials.