Co1-xNixSb3-ySey热电输运中晶界和点缺陷的耦合散射效应

Coupling scattering effect between grain boundary and point defect on the thermoelectric transport process in Co_(1-x)Ni_xSb_(3-y)Se_y

结合机械合金化与放电等离子烧结工艺制备了Ni和Se共掺的细晶方钴矿化合物Co1-xNixSb3-ySey,研究了晶界和点缺陷的耦合散射效应对CoSb3热电输运特性的影响.通过Ni掺杂优化载流子浓度提高功率因子.在x=0·1时,功率因子达到最大值1750μWm-1K-2(450℃),是没有掺Ni试样的两倍.晶界和点缺陷的耦合散射机理使晶格热导率急剧下降,其中Co0·9Ni0·1Sb2·85Se0·15的室温晶格热导率降低至1·67Wm-1K-1,接近目前单填充效应所能达到的最低值1·6Wm-1K-1,其热电优值ZT在450℃时达到最大值0·53.将Callaway-Von Baeyer点缺陷散射模型嵌入到Nan-Birringer有效介质理论模型,对晶界散射和点缺陷散射的耦合效应对热导率的影响进行了定量分析,模型计算与实验结果符合.理论模型计算表明,当晶粒尺寸下降到50nm同时掺杂引入点缺陷散射后,Co0·9Ni0·1Sb2·85Se0·15的晶格热导率下降到0·8Wm-1K-1.

Ni and Se co-doped skutterudite compounds Co1-xNixSb3-ySey with fine grains were fabricated by combining mechanical alloying and spark plasma sintering. The coupling effect between grain boundary scattering and point defect scattering on the thermoelectric transport properties was focused.The enhanced power factor by co-doping is twice that of the sample without Ni and achieved a maximum value of 1750μWm-1K-2 at 450℃ for x=0.1. Due to the coupling scattering effect, the lattice thermal conductivity at room temperature decreased to 1.67Wm^-1K^-1, which approach the reported minimum of 1.60 Wm^-1K^-1, whareas the improved ZT value reached 0.^53 at 450℃ for the Co0.9Ni0.1Sb2.85Se0.15. A suggested model shows that the decreased thermal conductivity is duc to the coupling effect between grain boundary scattering and point defect scattering, The calculated values are in good agreement with experimental results. The simulated results also suggest that the lattice thermal conductivity could be further decreased to 0.8Wm^-1K^-1 when the grain size was reduced to 50nm.