【作者】 胡淑红；

【导师】 赵新兵；

【作者基本信息】 浙江大学 ， 材料学， 2001， 博士

【摘要】 热电材料是一种将热能和电能直接转换的功能材料，在热电发电和致冷等领域具有极为重要的应用前景。Bi₂Te₃化合物及其固溶体合金是研究最早也是最成熟的热电材料之一，室温下其热电优值ZT=1，目前大多数致冷元件都是采用这类材料。基于Bi₂Te₃基热电材料的应用前景，本文采用新的合成技术和新思路设计材料成分，对BiTe基热电材料作了改进研究：鉴于稀土元素所具有的特殊的电子状态，首次通过机械合金化法（MA）成功地制备了BiTe基稀土镧的插层化合物，为BiTe基热电材料性能的改进和提高开辟了一条新的探索途径；利用聚苯胺导电高聚物所具有的较高的电导率/热导率（σ/κ），分别用机械共混和“原位吸附”聚合的方法制备了Bi_0.5Sb_1.5Te₃/聚苯胺（PAn）热电复合材料，提出有机/无机复合热电材料的概念。 研究表明：与熔炼样相比，机械合金化法制备的Bi₂Te₃型合金粉末样具有晶粒细小，成分均匀的优点，而细小的晶粒尺寸也使其电导率有所下降。 机械合金化法制备的掺稀土元素La的La₁₅Bi₃₄Te₅₁合金和掺过渡族元素Mn的Mn₁₅Bi₃₄Te₅₁合金的XRD分析表明，La₁₅Bi₃₄Te₅₁和Mn₁₅Bi₃₄Te₅₁分别在真空球磨100小时和150小时后实现合金化，且La₁₅Bi₃₄Te₅₁在真空球磨150小时后形成了纳米结构的合金。对La₁₅Bi₃₄Te₅₁合金的XRD结构分析表明镧原子插层进入了Bi₂Te₃化合物层状结构的Te-Te原子层间。La₁₅Bi₃₄Te₅₁纳米插层化合物Seebeck系数的测量表明当晶粒尺寸减小到纳米尺寸时，载流子散射机制有可能发生改变，从而导致La₁₅Bi₃₄Te₅₁合金Seebeck系数的大幅上升。 对机械共混法制备的Bi_0.5Sb_1.5Te₃/聚苯胺复合材料冷压样热电性能的测量表明：与Bi_0.5Sb_1.5Te₃材料相比，复合材料的Seebeck系数略有下降，但当聚苯胺含量再增加时，并未导致复合材料Seebeck系数进一步地大幅下降，这说明尽管聚苯胺本身具有的Seebeck系数值较低，但分散在基体中的聚苯胺弥散颗粒加强了载流子的散射，从而使得复合材料的Seebeck系数值并无显著下降；与Bi_0.5Sb_1.5Te₃材料相比，复合材料冷压样的电导率随聚苯胺含量的增加而迅速下降，是导致复合材料功率因子下降的主要原因。 对于聚苯胺含量为7％的复合材料，“原位吸附”聚合法制备的材料的电导率比机械共混法制备的相应材料的电导率值高约20％，功率因子高约13％，表明“原位吸附”聚合法与机械共混法相比，可有效地降低复合材料相与相之间的接触电阻，使 浙 江 大 学 傅 士 学 位 论 文材料获得较高的功率因子。更多还原

【Abstract】 Thermoelectric materials are those materials that directly convert heat to electricity or conversely, which are prospect using as the thermoelectric generators and cooling devices that is small in sizes, without noises and without any pollutions of the environment. Bi2Te3 compounds and their solid solutions have received considerable attention due to their great potential for application in refrigeration, the figure of merit of which is about 1. In this paper, the new approaches have been applied to improve the performance of the BiTe-based alloys. Special consideration has been made on the alloying with the rare earth elements, since they have an unusual electronic state called the intermediate valence state. It is first time to synthesize the Bi2Te3-based rare earth intercalated compounds by mechanical alloying (MA) in the present work. Bi0.5Sb1.5Tes/Polyaniline composites were also prepared and studied aimed to develop the low thermal conductive inorganic/organic thermoelectric composites.It is shown the electrical conductivity of the MA alloys powders are small in grain size and uniform in element dispersion in comparing with melting alloys, however fine grain sizes result also in the lower electrical conductivity.The XRD analyses of the La15Bi34Te51 and Mn15Bi34Te51 alloys prepared by MA showed that the LaisBi34Te51 and Mn15Bi34Te51 alloys were synthesized with vacuum milling for 100 and 150 hours, and the nanostructured La15Bi34tTe51 compounds were synthesized after milling for 150 hours. It was found by The XRD analyses that the lanthanum atoms have intercalated into the layer structure of BizTea host by 150 hours and 370癈 annealing of the La15Bi34Te51 alloy. The Seebeck coefficient of La15Bi34Te51 suggests that the carrier scattering mechanism must be changed when the grain sizes decreased to a few nanometers, which lead to the Seebeck coefficient increases dramatically.The experimental results on the Bi0.5Sb1.5Te3/Polyaniline composites prepared by mechanical blending showed that the polymer additives do not lead to any remarkable decrease on the Seebeck coefficients of the composites, which applies that the scattering of carries in the composites must be significantly enhanced due to the dispersed polymer powders, and so that the Seebeck coefficient of the composites remain comparable withthe Bio.sSbi.sTea alloy, although the polymer has a much small Seebeck coefficient than the Bio.sSbi.sTea alloy. However the electrical conductivity of the composites decreases dramatically, which leads to a remarkable descent on their power factors.It was found that the composites prepared by in-situ polymerization have a remarkable higher electrical conductivity and so that a higher power factor than those of the composites prepared by mechanical blending, which suggests that the method of the in-situ polymerization could be helpful to decreasing the resistance of the polymer/alloy interfaces.更多还原