铜铑氧化物基热电材料第一性原理计算与制备及掺杂热电性能

发布时间：2018-05-08 19:31

本文选题：铜铑基氧化物 + 热电材料　；参考：《昆明理工大学》2017年硕士论文

【摘要】：随着社会的高速发展,人类对能源需求量日益增加。尤其是进入21世纪以来,城市化和工业化的日益普及,能源危机更加严峻,环境污染愈显突出,已成为当今世界的两大难题。因此,寻找新型能源和新型能源材料,势在必行。热电材料是一种能实现热能和电能直接相互转化的新型环保型功能材料。热电材料尤其是氧化物热电材料具有无毒、无污染、无噪音、高温稳定性好等优点,在废热回收利用、太阳能吸收、以及热管理等方面具有广泛的应用前景。因此,近年来,热电材料已引起了广大研究者的密切关注。本文首先对热电材料的研究进展及应用前景等问题进行了阐述。然后以铜铑基氧化物热电材料为研究对象,计算了掺杂元素对其晶格热导率的影响,讨论了热电材料的制备方法、物理特性、性能表征、以及影响热电性能的参数。并通过掺杂改性对铜铑基热电氧化物热电材料的性能进行了系统研究。主要研究内容和实验结果可概括如下:简单介绍了实验中需要用到的热电性能参数主要测试仪器(钨灯丝扫描电子显微镜、X射线衍射仪、激光热导仪、高性能全自动赛贝克系数-电导测试系统)及其测试原理。利用 CASTEP 程序对 CuRh2-2xM2xO4 和 CuRh1-yMyO2(M=Cr、Co、Mg,x、y=0,0.05,0.1,0.15,0.2,0.25,0.3)的晶格热导率进行了第一性原理计算,得出以下结论:三种掺杂元素均可降低材料的晶格热导率,材料的晶格热导率也随着掺杂量的上升而下降,而且Mg元素掺杂对降低晶格热导率的效果最好。研究了样品制备工艺,结果表明:CuRh02是CuRh204的高温相,940℃C和980℃分别为CuRh2-2xMg2xO4和CuRh1-yMgyO2的最佳烧结温度,并通过固相反应法成功制备出了掺杂样品;但为了提高热电性能与检测需要,继续对各样品进行了放电等离子烧结。采用二步固相反应-放电等离子烧结法通过Rh位掺杂Mg位掺杂得到了一系列CuRh2-2xMg2xO4块体样品。分析了掺杂对材料的物相、形貌以及热电性能的影响。实验结果表明:微量掺杂对基体的结构和物相影响较小,当x0.25时,晶界间可能有第二相析出,影响了材料的电学性能,导致功率因子下降。CuRh2.2xMg2xO4的热导率、赛贝克系数、电导率均随掺杂量的上升而下降,功率因子最高的是CuRh1.6Mg0.404(在 900℃下达到了 165.53 μ W/mK-2),但 ZT 值最高的是 CuRh1.5Mg0.5O4,在 900℃时ZT最大值为:0.18。采用二步固相反应-放电等离子烧结法制备了一系列CuRh1-yMgyO2块体样品,并对其热电性能进行了表征测试。实验结果表明:制备粉末具有明显的层状结构。经过SPS烧结处理后,块体样品的致密度达理论密度的90%以上,晶粒尺寸随着Mg掺杂量的增加而减小。样品的热导率均随掺杂量的上升而下降,但赛贝克系数和电导率均随掺杂量的上升而上升。CuRh0.7Mg0.3O2的ZT值最高,900℃时最大值为0.21。本论文较为系统的研究了铜铑基氧化物热电材料,利用制备工艺、Mg元素掺杂等手段,不同程度的提高了其热电性能。研究结果表明铜铑基氧化物热电材料是一种很有潜质的材料体系,具有较高的研究价值和应用前景;同时为研发高性能氧化物热电材料提出了可供借鉴的理论支持和技术参考。
[Abstract]:With the rapid development of society, human demand for energy is increasing. Especially since twenty-first Century, the increasing popularity of urbanization and industrialization, the energy crisis is more severe, the environmental pollution is becoming more and more prominent, and it has become the two major problem in the world. Therefore, it is imperative to find new energy sources and new energy materials. The thermoelectric materials, especially oxide thermoelectric materials, have the advantages of non-toxic, pollution-free, no noise, high temperature stability, etc., and have extensive application prospects in waste heat recovery, solar absorption, and heat management. The research progress and application prospect of thermoelectric materials have been discussed in this paper. Then, the effects of the doped elements on the thermal conductivity of the lattice are calculated, and the preparation methods, physical properties and performance characterization of the thermoelectric materials are discussed. The properties of copper rhodium based thermoelectric thermoelectric materials are systematically studied by doping modification. The main research contents and experimental results can be summarized as follows: the main testing instruments used in the experiment are briefly introduced (tungsten filament scanning electron microscope, X ray diffractometer, excitation). Photothermal conductance, high performance fully automatic Seebeck coefficient - conductance test system and its testing principle. Using the CASTEP program, the thermal conductivity of CuRh2-2xM2xO4 and CuRh1-yMyO2 (M=Cr, Co, Mg, x, y=0,0.05,0.1,0.15,0.2,0.25,0.3) is calculated by the first principle, and the conclusion is that three kinds of doping elements can reduce the lattice heat of the material. The thermal conductivity of the material decreases with the increase of the doping amount, and the effect of doping Mg elements to reduce the thermal conductivity of the lattice is the best. The preparation process of the sample is studied. The results show that CuRh02 is the high temperature phase of CuRh204 and the optimum sintering temperature of CuRh2-2xMg2xO4 and CuRh1-yMgyO2 at 940, C and 980, respectively, and by the solid state reaction method. The doped samples were successfully prepared, but in order to improve the thermoelectric properties and detection needs, the samples were continuously sintered by discharge plasma. A series of CuRh2-2xMg2xO4 bulk samples were obtained by doping the Rh bit doping Mg bit with the two step solid state reaction discharge plasma sintering method. The phase, morphology and thermoelectric properties of the doped materials were analyzed. The experimental results show that micro doping has little influence on the structure and phase of the matrix. When x0.25, there may be a second phase precipitation between the grain boundaries, which affects the electrical properties of the material, which leads to the decrease of the thermal conductivity of the power factor of the.CuRh2.2xMg2xO4, the asbeck coefficient and the electrical conductivity are all decreased with the increase of the doping amount, and the highest power factor is the increase of the power factor. CuRh1.6Mg0.404 (reached 165.53 W/mK-2 at 900 C), but the highest ZT value is CuRh1.5Mg0.5O4. At 900, the maximum ZT value is: 0.18. using two step solid state reaction discharge plasma sintering method to prepare a series of CuRh1-yMgyO2 block samples, and the thermoelectric properties are characterized and tested. The experimental results show that the powder is prepared. After SPS sintering, the density of the sample is more than 90% of the theoretical density, and the grain size decreases with the increase of Mg doping. The thermal conductivity of the sample decreases with the increase of the doping amount, but the Sibeck coefficient and the conductivity increase with the doping amount and the ZT value of.CuRh0.7Mg0.3O2 is the highest, 900. The maximum value of C (0.21.) is a systematic study of copper rhodium oxide thermoelectric materials. The thermoelectric properties are improved by means of preparation technology and Mg element doping. The results show that the copper rhodium oxide thermoelectric material is a very latent material system, which has high research value and application prospect. At the same time, it provides a theoretical support and technical reference for developing high performance oxide thermoelectric materials.

【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB34

【参考文献】