Sr掺杂CdO多晶块体的高温热电性能

High temperature thermoelectric performance of Sr doped CdO polycrystalline bulks

本文利用传统固相烧结法制备了Cd1?xSrxO(x=0,0.01,0.03,0.05)多晶块体并研究了Sr掺杂对Cd O高温热电性能的影响.在Cd O中掺杂Sr O会使样品的载流子浓度降低,导致其电阻率和塞贝克系数绝对值增大.同时,Sr的引入抑制了Cd O多晶的晶粒生长,导致其尺寸减小、晶界增多.随着Sr掺杂浓度的提高,样品的电子热导率和声子热导率均呈现出下降趋势,使得总热导率大幅度降低,Cd0.95Sr0.05O样品的热导率在1000 K时仅为1.71 W m?1 K?1,低于多数氧化物热电材料.由于总热导率的降低,所有掺杂样品的热电性能均得到了提升,其中,Cd0.97Sr0.03O多晶样品在1000 K时的ZT值达到了0.40,比非掺杂Cd O多晶样品提高了25%,可与目前报道的最好的n型氧化物热电材料相比拟.

In this paper, Cd1-xSrxO polycrystalline bulks were synthesized via conventional solid state reaction method and the effect of Sr doping on the high temperature thermoelectric performance of Cd O were investigated. XRD results revealed all samples were pure Cd O and the lattice parameters increased with Sr content, demonstrating that all doped Sr entered the Cd O lattice. The dopant Sr inhibited the grain growth of Cd O polycrystals, gave rise to the reduction of grain size as well as increase of grain boundaries. Due to the large difference on electrical affinities of Cd O and Sr O, the introduction of Sr O into Cd O polycrystals resulted in decreased carrier concentration, which further led to the increment of both electrical resistivity and Seebeck coefficient. Experimental data on thermal properties verified that doping of Sr was an effective way to reduce the thermal conductivity of Cd O. Attributing to the increased electrical resistivity, the electrical thermal conductivity decreased significantly with increasing Sr content. On the other hand, the long-wavelength phonon scattering was greatly enhanced by increased grain boundaries, resulted in suppressed phonon thermal conductivity. Meanwhile, the size and mass differences on Sr and Cd atoms led to strong strain field fluctuation scattering and mass fluctuation scattering, which drastically reduced the phonon thermal conductivity. Benefiting from the decreased electrical and phonon thermal conductivities, the total thermal conductivity experienced a remarkable reduction, from 3.52 W m^-1 K^-1 for the pristine Cd O to 1.71 W m^-1 K^-1 for the Cd0.95Sr0.05 O at 1000 K, lower than most oxide thermoelectric materials. Originating from the reduced thermal conductivity, the thermoelectric performances of all doped samples were promoted, the Cd0.97Sr0.03 O sample reached the highest ZT value of 0.40 at 1000 K despite of the low power factor, which was 25% higher compared to pure Cd O, and was comparable to the best reported n type oxide thermoelectric materials.