稀土元素Ce填充p型方钴矿化合物的热电性能

用高温熔融-退火扩散法合成了富Co组成的方钴矿化合物CeyFexCo4-xSb12(y=0～0.42),并对化合物的结构和热电性能进行了研究.结果表明:化合物的晶格常数随Ce填充量的增加而线性增加.霍尔系数RH为正值,CeyFexCo4-xSb12化合物表现p型传导.载流子浓度和电导率随Ce填充量的增加而减少.Seebeck系数随Ce填充量的增加及温度的上升而增加.晶格热导率在Ce填充量约为0.29时达到最小值,说明在Sb组成的二十面体空洞中部分填充时,Ce的扰动对声子的散射作用最强.在725K时,组成为Ce0.29Fe1.41Co2.59Sb12.32化合物的最大无量纲热电性能指数达到0.65.     

p型方钴矿化合物BayFeCo3Sb12的热电性能研究

用两步固相反应法合成了单相的p型BayFeCo3Sb12化合物,并系统地研究了Ba不同填充分数对方钴矿化合物热电性能的影响:化合物载流子浓度强烈地依赖于填充原子的填充分数,随Ba填充分数y的增加,载流子浓度及电导率降低;塞贝克系数随温度T的上升而增加,比CoSb3的塞贝克系数有一定程度的提高,尤其是在中温部分有大幅度提高,得到的最大塞贝克系数由CoSb3的107μVK-1提高到Ba1.0FeCo3Sb12的235μVK-1晶格热导率随Ba的填充分数y的增加而进一步下降,Ba08FeCo3Sb12甚至降到2.2 Wm1K1;Ba08FeCo3Sb12化合物显示最大热电性能指数,在850K左右其最大无量纲热电性能指数ZT值达0.75.     

High-Temperature Thermoelectric Properties of p-Type Yb-Filled Skutterudite Nanocomposites with FeSb2 Nanoinclusions

Bulk thermoelectric (TE) nanocomposite materials have attracted considerable attention due to their great potential to exhibit higher dimensionless figure of merit ZT. Filled skutterudites of both n-type and p-type have already demonstrated their excellent high-temperature TE performance, good mechanical properties, and thermal stability. Herein, we extend this work to Yb-filled p-type skutterudite nanocomposites with in?situ precipitated FeSb₂ nanoinclusions. Such a nanocomposite material can be easily synthesized by fine control of starting stoichiometry and the subsequent heat treatment process. By taking advantage of these naturally occurring FeSb₂ nanoparticles, we achieve ZT _max?=?0.74 in Yb_0.6Fe₂Co₂Sb₁₂/0.05FeSb₂ at 780?K. We apply the method of four coefficients to calculate the density-of-states effective mass and the carrier scattering parameter. We find that a larger effective mass induced by the presence of nanoparticles is the origin of the enhanced Seebeck coefficient.     

Effect of Cyclic Thermal Loading on the Microstructure and Thermoelectric Properties of CoSb<Subscript>3</Subscript>

The effect of cyclic thermal loading on the microstructure and thermoelectric properties of CoSb₃ was investigated. The microstructures of the samples were characterized by x-ray diffractometry, scanning electron microscopy, energy dispersive x-ray spectrometry and density measurements. The electrical conductivity, the Seebeck coefficient and the thermal conductivity were measured from room temperature to 800 K. Under cyclic thermal loading, antimony partially volatilized from the surface of the sample, and the density obviously decreased. After 2000 cycles, the phase composition of the sample remained stable, and the average grain size did not change significantly. Moreover, the electrical conductivity varied only slightly, except in the low temperature region. The Seebeck coefficient decreased slightly. However, the thermal conductivity changed remarkably with increasing numbers of thermal cycles.     

Effects of Excess Sb on Thermoelectric Properties of Barium and Indium Double-Filled Iron-Based p-Type Skutterudite Materials

A series of Ba and In double-filled iron-based p-type skutterudite thermoelectric (TE) materials with nominal composition BaInFe_3.7Co_0.3Sb_12+m (0.72????m????2.4) have been prepared by melting, quenching, annealing, and spark plasma sintering (SPS) methods. The effects of excess Sb on the phase composition, microstructure, and TE transport properties of these materials were investigated in this work. All the SPS bulk materials are composed of the main skutterudite phase and trace InSb and FeSb₂. The content of FeSb₂ in the SPS bulk materials gradually decreased and that of InSb remained nearly invariable with increasing m. The impurities InSb and metallic Sb are found at grain boundaries. The amount of metallic Sb at grain boundaries gradually increased with increasing m. The excess Sb had no effect on the growth of grains. The dependence of the TE properties on m indicates that preventing the formation of FeSb₂ by adjusting the excess Sb value may significantly improve the TE properties of Ba and In double-filled iron-based p-type skutterudite materials. The significant increases in the carrier concentration and electrical conductivity as well as the remarkable reduction in the lattice thermal conductivity of the sample with m?=?0.96 are due to the significant reduction in the FeSb₂ content induced by the excess Sb. The gradual increase in ZT with increasing m from 0.72 to 1.44 is attributed to the gradual decrease of the FeSb₂ content, and the gradual decrease in ZT in the m range of 1.44 to 2.4 is due to the gradual increase of the Sb content in the Sb-In alloy impurity occurring at grain boundaries. The lowest lattice thermal conductivity of 0.31?W?m^?1?K^?1 and the highest ZT value of 0.63 were obtained at 800?K for the sample with m?=?1.44.     

制备工艺对新型热电材料制冷性能的影响

通过取点法得到了由Ingot法、BM法、S-MS法和Te-MS法制备的四种新型p型热电材料(Bi0.5Sb1.5)Te3的变物性参数拟合公式,分析了温度对不同方法制备的热电材料的影响,得到了热电材料无量纲优值与绝对温度的关系曲线.从热力学方面研究了制备工艺对基于新型热电材料的热电制冷器最大制冷系数的影响.结果表明:由Te-MS法制备的新型p型热电材料(Bi0.5Sb1.5)Te3具有最大的优值系数,基于该材料的热电制冷器最大制冷系数可达2.49,较其他三种方法制备的热电材料分别提升了 34.59％,37.57％和25.76％.