CdO多晶块体热电性能优化研究

发布时间：2018-07-14 21:11

【摘要】：CdO是一种N型半导体材料,具有抗氧化、高温稳定性好、原材料价格低廉等诸多优点,在高温热电领域具有潜在应用前景。本论文首次研究了元素双掺、纳米复合、多孔结构对CdO多晶块体材料电、热输运性能的影响规律和物理机制,以期通过电、热输运参量的调控来提高CdO的高温热电性能。论文主要内容和结论如下:1.利用固相反应烧结技术制备了Mg/Ca双掺的CdO多晶块体并研究了掺杂浓度对样品电、热输运性能的影响。实验发现,Mg/Ca双掺在不显著降低CdO功率因子的前提下可以大幅降低其热导率,使热电性能得以优化。在最佳掺杂浓度下(3%Mg/Ca),样品在1000 K时的热电优值为0.5,比未掺杂的样品提高了约50%。2.利用固相反应烧结技术制备了纳米Ag颗粒复合的CdO多晶块体并研究了纳米复合对样品电、热输运性能的影响。一方面,纳米Ag颗粒的掺入可以提升CdO的功率因子,这可能源于和能量有关的散射增强导致的载流子能量过滤效应;另一方面,纳米Ag颗粒的掺入会引入大量的纳米第二相、晶界和界面,使声子的散射增强,热导率降低。功率因子和热导率的同时优化使得CdO:Ag样品具有较高的热电优值,1000 K时,CdO:3at%Ag样品的ZT值达到了0.43。3.通过向CdO中掺入有机物PMMA制备了多孔结构的CdO多晶块体并研究了PMMA掺入量对样品电、热输运性能的影响。随着PMMA的掺入,样品的孔隙率增多而平均晶粒粒度减小,导致其热导率大幅下降。尽管这些微米孔的引入也使CdO的功率因子受到影响,但最终因热导率的大幅降低而使热电优值得以提升。1000 K时,5%PMMA掺入的CdO多晶块体的ZT值达到了0.51。
[Abstract]:CDO is a kind of N-type semiconductor material, which has many advantages such as oxidation resistance, high temperature stability, low cost of raw materials and so on, so it has a potential application prospect in the field of high temperature thermoelectricity. In this paper, the effect of double doped elements, nanocomposites and porous structures on the electrical and thermal transport properties of CdO polycrystalline bulk materials is studied for the first time, and the physical mechanism is studied in order to improve the high temperature thermoelectric properties of CdO by regulating the electrical and thermal transport parameters. The main contents and conclusions are as follows: 1. The Mg- / Ca doped CdO polycrystalline bulk was prepared by solid state reaction sintering and the effect of doping concentration on the electrical and thermal transport properties of the samples was investigated. It is found that the thermal conductivity can be greatly reduced and the thermoelectric properties can be optimized by adding mg / Ca without significantly reducing the power factor of CdO. At the optimum doping concentration (3mg / Ca), the thermoelectric excellent value of the sample at 1000 K is 0.5, which is about 50. 2% higher than that of the undoped sample. Nanocrystalline Ag composite CdO polycrystalline bulk was prepared by solid state reaction sintering and the effect of nano-composite on the electrical and thermal transport properties of the samples was studied. On the one hand, the incorporation of nano-Ag particles can enhance the power factor of CdO, which may be due to the carrier energy filtering effect caused by the enhanced scattering related to energy; on the other hand, the incorporation of nano-Ag particles will introduce a large number of nanometer-second phases. Grain boundary and interface increase phonon scattering and decrease thermal conductivity. When the power factor and thermal conductivity are optimized simultaneously, the ZT value of CdO _ (10) O _ (3) AT Ag sample reaches 0.43.3 at 1000K. Porous CdO polycrystalline bulk was prepared by incorporation of organic compounds PMMA into CdO and the effect of PMMA incorporation on the electrical and thermal transport properties of the samples was investigated. With the incorporation of PMMA, the porosity of the sample increases and the average grain size decreases, which results in a significant decrease in the thermal conductivity of the sample. Although the introduction of these micron pores also affected the power factor of CdO, the ZT value of CdO polycrystalline bulk doped with 5 PMMA reached 0.51when the thermoelectric excellent value was raised by the decrease of thermal conductivity.
【学位授予单位】：河北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN304.21

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