方钴矿的界面调控与热电性能

发布时间：2018-05-14 03:14

本文选题：方钴矿 + 液相压实　；参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：方钴矿热电材料是综合性能较好的中温热电材料,由于具有较大的载流子迁移率和Seebeck系数,使其具备高ZT值的潜力,但由于晶格热导率较高,导致ZT值较低,本文主要通过高能球磨纳米化、引入石墨烯、液相压实构建小角晶界等界面调控方式,降低晶格热导率,从而提高热电性能。采用XRD、SEM、TEM、激光热导仪、电导率/塞贝克系数测试系统等方法研究了不同界面调控方式对方钴矿组织结构和热电性能的影响规律,得到如下研究成果:针对退火La0.8Ti0.1Ga0.1Fe3CoSb12方钻矿,采用高能球磨结合放电等离子体烧结(SPS)制备纳米结构块体材料,与参比样品相比,退火球磨样品的电导率基本一致,但塞贝克系数增大,相应功率因子也较高。退火球磨样品结构纳米化增强了对声子的散射作用,降低了晶格热导率,623K时晶格热导率达到最低为0.8Wm-1K-1,较参比样品降低了 33%。通过高能球磨实现结构的纳米化不仅改善了电性能,也有效地降低晶格热导率,进而提高了热电性能,退火球磨样品的热电优值在723K时从0.8提升到1.05。采用PECVD法在p型退火La0.8Ti0.1Ga0.1Fe3CoSb12方钻矿粉体表面原位组装石墨烯,制备出p型方钻矿/石墨烯复合材料,发现石墨烯的引入对p型La0.8Ti0.1Ga0.1Fe3CoSb12方钻矿的电导率无明显影响,但塞贝克系数略有提高。石墨烯的引入明显降低p型La0.8Ti0.1Ga0.1Fe3CoSb12方钴矿的晶格热导率,673K时具有最低值为0.9Wm-1K-1,较参比样品降低了 25%。石墨烯的引入对电性能稍有改善的同时,明显降低晶格热导率,使ZT值在723K时从0.8提高到1.00。采用熔体旋甩结合液相压实法制备n型CexCo4Sb14.4(x=0.1、0.125、0.15、0.175、0.2)方钴矿,发现电导率随着填充量的增加而增大,Seebeck系数与电导率的变化趋势相反,填充量为x=0.15的样品具有最高的PF,约为45.7μWcm-1K-2。热导率和晶格热导率均随着填充量的增加先减小后增大,填充量为x=0.15的样品具有最低热导率约为3.08Wm-1K-1。Ce0.15Co4Sb14.4样品在773K时ZT值最高为1.15。
[Abstract]:The thermoelectric material of galactic cobalt mine is a medium temperature thermoelectric material with good comprehensive properties. Because of its large carrier mobility and Seebeck coefficient, it has the potential of high ZT value. However, due to the high lattice thermal conductivity, the ZT value is lower. In this paper, interface regulation methods such as high energy ball milling nanocrystallization, introduction of graphene and liquid phase compaction to construct small angle grain boundaries are used to reduce lattice thermal conductivity and improve thermoelectric properties. The effects of different interface regulation methods on the microstructure and thermoelectric properties of cobalt ore were studied by means of XRDX SEMMOTEM, laser thermal conductivity meter and conductivity / Seebeck coefficient test system. The results are as follows: for annealed La0.8Ti0.1Ga0.1Fe3CoSb12 square drill, Nanostructured bulk materials were prepared by high energy ball milling combined with discharge plasma sintering (SPS). Compared with the reference samples, the electrical conductivity of the annealed ball-milling samples was basically the same, but the Seebeck coefficient was increased and the corresponding power factor was higher. The nanocrystalline structure of annealed ball-milling samples enhances the scattering of phonons and reduces the lattice thermal conductivity to the lowest 0.8Wm-1K-1 when the lattice thermal conductivity is reduced to 623K, which is 33% lower than that of the reference samples. The nanocrystalline structure achieved by high energy ball milling not only improves the electrical properties, but also reduces the lattice thermal conductivity effectively, and then improves the thermoelectric properties of the annealed ball-milling samples from 0.8 to 1.05 at 723K. Graphene was prepared by in-situ assembly of graphene on the surface of p-type La0.8Ti0.1Ga0.1Fe3CoSb12 square drill powder by PECVD method. It was found that the introduction of graphene had no obvious effect on the conductivity of p-type La0.8Ti0.1Ga0.1Fe3CoSb12 square drill. But Seebeck's coefficient increased slightly. The introduction of graphene can obviously reduce the lattice thermal conductivity of p-type La0.8Ti0.1Ga0.1Fe3CoSb12 galactic cobalt ore with a minimum value of 0.9Wm-1K-1, which is 25% lower than that of the reference sample. With the introduction of graphene, the electrical properties were improved slightly, and the lattice thermal conductivity was obviously decreased, and the ZT value increased from 0.8 to 1.00 at 723K. N type CexCo4Sb14.4 (0.125U 0.125U 0.175U 0.2) cobalt ore was prepared by melt rotation and liquid compaction. It was found that the conductivity increased with the increase of filling amount and the change trend of conductivity was opposite. The sample filled with xc0.15 had the highest PFF (about 45.7 渭 Wcm-1K-2). The thermal conductivity and lattice thermal conductivity decrease firstly and then increase with the increase of filling amount. The lowest thermal conductivity of 3.08Wm-1K-1.Ce0.15Co4Sb14.4 sample is about 1.15 at 773K.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB34

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