【作者】 金仁成；

【导师】 陈刚；

【作者基本信息】 哈尔滨工业大学 ， 化学工程与技术， 2012， 博士

【摘要】 热电材料是一种可以实现热能和电能直接相互转换的特殊功能材料。由该类材料制备的热电器件可有效回收利用化石能源燃烧过程中产生的废热，因而可有效缓解当前全球能源危机和环境污染。但由于现有热电材料的能量转换效率较低，离实际应用尚有较大的差距。因此，提高材料的热电转换效率是当前热电材料研究的重点。研究表明，低维化可显著提高材料的热电优值，而低维化的铅、锑硫族化物热电材料正是由于具有较高的热电性能成为该领域的研究热点。故此，本论文选择铅、锑硫族化物作为研究对象，旨在通过简单溶剂热法制备具有不同纳米结构的铅、锑硫族化物热电材料，通过X射线衍射、扫描电子显微镜、透射电子显微镜以及电学性能测试系统对其形成机制及电学性能进行系统研究。在无模板剂和表面活性剂条件下制备了PbS纳米棒，考察了其生长机制。研究发现，纳米棒是由小纳米立方通过取向连接而成。并以此为基础，采用二次水热法制备了具有核壳结构的PbS/PbTe纳米棒。采用热电综合测试系统对所制备的样品进行了电学性能测试。结果表明：核壳结构PbS/PbTe纳米棒的功率因子高于纯相PbS；且发现PbS/PbTe纳米棒的热电性能可通过改变PbS/Te比进行可控调节。以硫代乙醇酸为表面活性剂和硫源制备了具有两相纳米结构的PbS/PbSe空心球，研究了不同反应因素对形貌的影响。结果发现，在硫代乙醇酸的辅助下，PbS和PbSe纳米粒子会相互聚集形成PbS/PbSe空心球，表现出典型的自组装机制伴随奥斯特瓦尔德熟化机制。电学性能测试发现，PbS/PbSe空心球的电导率和Seebeck系数在整个测试温度范围内（300-600K）均高于PbSe纳米粒子，并在500K时其功率因子达到最大值205.4μW/（K²·m），相当于纯相PbSe纳米粒子的两倍。以葡萄糖为表面活性剂制备了花状形貌PbTe晶体，研究了不同反应因素对产物形貌的影响。发现花状PbTe晶体的形成机制为奥斯特瓦尔德熟化伴随异向生长机制。并在此基础上，以亚硒酸钠替代部分亚碲酸钠，采用相同方法制备了花状PbSe/PbTe纳米晶。研究发现组成花状形貌的纳米片是由尺寸小于30nm的PbSe和PbTe纳米晶组成，同时Se和Te之间能够发生取代反应。对样品进行电学性能测试发现，PbSe/PbTe纳米晶的电导率在常温时高达40S/m，与100nm PbTe纳米粒子和6nm PbTe薄膜相比，其电导率提高了1个和3个数量级。以葡萄糖（柠檬酸）为表面活性剂制备了分级结构Sb₂Se₃和Sb₂Te₃晶体。研究发现，葡萄糖和柠檬酸在Sb₂Se₃和Sb₂Te₃的形成过程中起到了至关重要的作用。在反应体系中，葡萄糖和柠檬酸作为表面活性剂吸附在Sb₂Se₃和Sb₂Te₃的晶核上，且在葡萄糖和柠檬酸中氢键以及静电的相互作用下纳米粒子发生相互聚集；同时表面活性剂分子能够吸附在某些晶面上限制了晶面的生长，从而形成具有分级结构的Sb₂Se₃和Sb₂Te₃晶体。电学性能测试发现，Sb₂Se₃样品的Seebeck系数和形貌有关，蠕虫状形貌的Sb₂Se₃样品Seebeck系数最高，在350K时可达1400μV/K。而Sb₂Te₃样品的Seebeck系数和电导率则与样品尺寸有较大关系。表现为尺寸较大的样品具有较大电导率，但却具有较小的Seebeck系数。更多还原

【Abstract】 Thermoelectric materials is a kind of special functional material which canconvert the heat source into electricity directly. By means of thermoelectric devices,the waste heat coming from the combustion of fossil fuel can be recycled, and thenthe utilization can be enhanced. However, due to the low thermoelectric figure ofmerit, the thermoelectric materials are still far way from practical application. Thus,the enhancement of the thermoelectric figure of merit is the key point in the field ofthermoelectric materials. Theoretical simulations and experimental results indicatethat the thermoelectric performance will be remarkbly enhanced in low dimensionalsystem. Lead and antimony chalcogenides have been attracted much attentionbecause of their high thermoelectric performances. In this paper, the lead andantimony chalcogenides were selected as the research objects, and the lead andantimony chalcogenides nanomaterials with different morphologies were fabricatedand the formation mechanisms and electrical properties were studied by X-raydiffraction, scaning electron microscope, Transmission electron microscope andelectrical property testing system.Without using any template and surfactant, lead sulfide nanorod was preparedthe formation mechanism was investigated in detail. And we discovered that thenanorods were composed of nanocubes through an oriented attachment process. Byusing tellurium and sodium hydroxide as precursors, the core-shell structuralPbS/PbTe nanorods were fabricated via a hydrothermal route. The electricalproperties of the obtained samples were investigated by a self-desinedthermoelectric test system, and the results indicated that the core-shell structuralPbS/PbTe nanorods have the higher power factors compared with that of pure phasePbS. Meanwhile, the thermoelectric properties of PbS/PbTe nanorods can be tunedby changing the molar ratio of PbS and Te.By using thioglycollic acid as a surfactant and sulfur source, binary phasedPbS/PbSe hollow spheres were fabricated and the reaction parameters influencingthe morphology were discussed systematically. The experimental results presentedthat these PbS and PbSe nanoparticles can aggregate together to form PbS/PbSehollow spheres with the assistance of thioglycollic acid, which can be named asclassical self assembly process accompanied by Ostwald ripening process. Moreover,electrical properties measurements demonstrated that the obtained PbS/PbSe hollowspheres had the higher electrical conductivity and Seebeck coefficient than that ofPbSe nanoparticles in the temperature range of300-600K. The maximum powerfactor of205.4μW/（K²·m） can be achieved at500K for PbS/PbSe hollow spheres, which is two times higher than that of PbSe nanoparticles.By using glucose as a surfactant, the flower-like PbTe crystals were synsthsizedand the different reaction factors influencing the morphology were systematicallyinvestigated. Based on the experimental results, a possible formation mechanism ofOstwald ripening accompanied by anisotropic growth mechanism was proposed.When sodium selenite was added into reaction system instead of part of sodimtellurite, the flower-like PbSe/PbTe nanocrystals were fabricated by a solvothermalmethod. The experimental results displayed that the nanopaltes were composed ofPbSe and PbTe nanocrystals with the size less than30nm, simultaneously, thesubstitution of Se and Te elements could be observed. The electrical properties testsdemonstrated that the electrical conductivity of40S/m can be achieved, which isone and three times higher than than that of100nm PbTe nanoparticles and6nmPbTe film, respectively.The hierachical Sb₂Se₃and Sb₂Te₃crystlas were fabricated with the help ofglucose or citric acid. Experimental results described that the glucose and citric acidmolecules played a crucial role in the formation of hierachical Sb₂Se₃and Sb₂Te₃crystlas. Glucose and citric acid molecules used as surfactants can be absorbed ontothe surface of Sb₂Se₃and Sb₂Te₃nuclei, which promoted the aggregation the thenanoparticles due to their hydrogen bonds and electrostatic effects. Meanwhile, themolecules can also be adsorbed onto some crystal surfaces of materials, whichprohibited the growth rate of these surfaces, thus, hierachical Sb₂Se₃and Sb₂Te₃crystlas can be obtained. The electrical properties measurements indicated that thethe morphology of Sb₂Se₃samples had much impact on the Seecek coefficients. Theworm-like Sb₂Se₃has the maximum Seecek coefficient, which can reach to1400μV/K at350K. The Seecek coefficients and the electrical conductivites are relatedto the size of Sb₂Te₃crystals, the sample with bigger size has the higher electricalconductivity and lower Seecek coefficient.更多还原