Fe置换CoSb3基热电材料的原位反应合成及电性能

以Co,Sb和Fe粉为原料,采用放电等离子烧结（SPS）技术在300-600℃温度范围内研究原位反应合成富Co基Skutterudite化合物FexCo4-xSB12（x=1．0）的合成条件,并对化合物的结构、微观形貌及热电性能进行研究。结果表明：在x=O～1．0范围内,300℃时开始生成少量的FexC04-xSb12：在400-600℃范围内,FexCp6-xSb12相为主晶相,并伴有极少量Sb相;化合物的品格常数随Fe含量的增加而线性增加;在600℃合成的FexCo4-xSb12化合物,当Fe含量小于0．3时,基本上以规则的颗粒和柱状晶生长,当Fe含量x大于0．3时,随着Fe含量的增加,颗粒和柱状晶减少,趋向于弯曲枝状晶生长：FexCp6-xSb12的电导率随着Fe置换量的增加而增加,Seebeck系数和功率因子的极值随着Fe置换量的增加而向高温方向移动。     

Effects of praseodymium doping on thermoelectric transport properties of CaMnO3 compound system

The rare earth Pr doped Ca1-x Prx MnO3(x=0,0.06,0.08,0.1,0.12,and 0.14) compound bulk samples were prepared to study the effect of Pr doping on thermoelectric transport properties of CaMnO3 compound system.The doped samples exhibited single phase composition within the experimental doping range,with condensed bulk microstructure and small porosities.The electrical resistivity was remarkably reduced for doped samples,on account of the enhanced carrier concentration;the absolute value of Seebeck coefficient was deteriorated mainly due to enhanced electron carrier concentration.The electrical performances of the doped samples reflected by resistivity and Seebeck coefficient fluctuations were optimistically tuned,with an optimized power factor value of 0.342 mW/(m·K2) at 873 K for x=0.08 sample,which was very much higher comparing with that of the un-doped sample.The lattice thermal conduction was really confined,leading to distinctly repressed total thermal conductivity.The thermoelectric performance was noticeably improved by Pr doping and the dimensionless figure of merit ZT for the Ca0.92 Pr0.08 MnO3 compound was favorably optimized with the maximum value 0.16 at 873 K.     

稀土掺杂对CaMnO3氧化物电传输性能的影响

采用柠檬酸溶胶凝胶结合陶瓷烧结工艺制备了Ca位掺杂稀土的Ca0.95RE0.05MnO3(RE=Pr,Eu,Tb)氧化物块体试样,并通过X射线衍射、扫描电子显微镜及电输运参数测试仪分析了所得试样。结果表明:所有试样呈单一物相,掺杂氧化物晶胞减小,块体试样结构致密;未掺杂的CaMnO3呈半导体传输特性,其电阻率较高,在373K时达340 mΩ.cm;Ca位掺杂稀土元素Pr,Eu,Tb之后,其电阻率大幅度降低,但各温度点电阻率随Pr,Eu,Tb略有升高;测试温度范围内所有掺杂试样载流子激活能降低,输运特性未发生改变;其中Pr掺杂试样Ca0.95Pr0.05MnO3各温度点的电阻率最低,在373K时为最低8 mΩ.cm,远低于未掺杂氧化物。     

烧结工艺对Ca3Co4O9基热电氧化物电性能的影响

采用溶胶-凝胶化学法合成了Ca3Co4O9热电氧化物粉末,分别采用陶瓷烧结工艺方法和放电等离子烧结(Spark Plasma Sintering,SPS)的方法制备了Ca3Co4O9热电氧化物块体材料.利用X射线衍射XRD、扫描电子显微镜SEM和电输运参数测试仪分析了所得样品的物相、微观组织结构、晶粒取向度和电输运性能.结果表明,不同制备方法均可得到纯相的Ca3Co4O9热电氧化物块体材料;通过陶瓷烧结工艺方法制备的Ca3Co4O9热电氧化物块体晶粒取向度较低,但随着成型压力的增加而提高;SPS烧结的方法制备的Ca3Co4O9热电氧化物块体晶粒取向度最高;试样电性能随着晶粒取向度的提高逐渐提高,其中SPS烧结方法制备的块体材料电性能最高,在测试温度最高点700℃时功率因子达3.85 μWmK-2,远高于普通烧结试样.     

氧化物热电材料研究进展

介绍了氧化物热电材料的应用前景,重点讨论了以NaCo2O4为代表的氧化物热电材料的基本结构、性能特征与研究进展;评述了NaCo2O4材料Na住、Co位掺杂研究和NaCo2O4材料研究中存在的问题;并介绍了几种其它氧化物热电材料的研究情况.     

放电等离子烧结制备Ca3Co4O9陶瓷及其电学性能

采用化学共沉淀与放电等离子烧结相结合的方法制备了Ca3Co4O9陶瓷.通过X射线衍射,红外光谱仪,扫描电镜等表征手段,探讨了Ca3Co4O9的形成过程,研究了不同制备工艺对陶瓷的物相,显微结构和性能的影响.实验结果表明共沉淀前驱物800℃预烧6 h或8 h后,再经放电等离子850℃,压力30 MPa下烧结5 min,可以获得纯相Ca3Co4O9陶瓷;800℃预烧6 h的烧结体密度为4.53 g/cm3,800℃预烧8 h的烧结体密度为4.78 g/cm3;前驱物预烧8 h后再经放电等离子烧结的块体具有较好的电学性能.700℃时,电阻率为8.30×10-5 Ωm,Seebeck系数为182μV/K.电导率和Seebeck系数在目前Ca-Co-O材料中是较高的.     

高锰硅热电材料的微观结构及电热输运性能

采用熔炼、退火结合放电等离子烧结的方法制备了名义成分为MnSi_x ( x=1.60、1.65、1.68、1.73、1.81、1.85 )的高锰硅(HMS, Higher Manganese Silicide)块体材料. 物相分析结果表明, 随着Si初始用量x的增加, HMS (Mn₁₅Si₂₆)相各衍射峰强度先增强后减弱. 当x<1.73时, 样品物相组成为HMS相和少量MnSi相, 当x≥1.73时, 样品物相组成为HMS相和少量Si相. 体系的热电性能受MnSi相和Si相的影响, 热电性能分析结果表明: 随着Si名义含量x的增大, 试样电导率逐渐降低, 赛贝克系数逐渐增大, 热导率先降低后增高. 其中, 名义成分为MnSi_1.68的试样由于具有最高的电性能(功率因子)和较低的热导率, 从而具有最好的热电性能, 在400℃时其无量纲ZT值达到0.36.     

快淬和球磨时间对p型(Bi_(0.25)Sb_(0.75))_2Te_3合金热电性能的影响

通过快淬-机械球磨-放电等离子烧结工艺制备了p型(Bi0.25Sb0.75)2Te3块体热电材料.在300~523K温度范围内对其电导率、Seebeck系数和热导率进行了测试,并系统研究了快淬后球磨时间对合金热电性能的影响.研究结果表明,随着球磨时间的延长,样品的电导率呈先降后升的趋势,Seebeck系数变化并不明显,而热导率随球磨时间的延长逐渐下降.球磨20h的样品在室温下具有最高的热电优值,最大值达到0.96,机械抗弯强度达到91MPa.     

四氢呋喃均聚醚的制备

本文介绍了四氢呋喃开环聚合反应的催化剂体系,并对目前较的杂多酸和固体超强酸催化剂在均聚醚合成中的应用做了较详细的阐述。     

Preparation and thermoelectric transport properties of Ba-, La- and Ag- doped Ca3Co4O9 oxide materials

The Ba-, La- and Ag-doped polycrystalline Ca2.9M0.1Co4O9 (M=Ca, Ba, La, Ag) thermoelectric bulk samples were prepared via citrate acid sol-gel synthesis method followed by spark plasma sintering technique. The bulk samples were characterized and analyzed with regard to their phase compositions, grain orientations as well as microstructures. The high temperature thermoelectric transport properties of the bulk samples were studied in detail. All bulk samples were found to be single-phased with modified body texture. The electrical resistivity was modulated as a result of carrier concentration modification, however the carrier transport process was not influenced; the Seebeck coefficient was deteriorated simultaneously. The total thermal conductivity was remarkably reduced, on account of the decreasing of phonon thermal conductivity. The thermoelectric properties of the Ba-, La-, and Ag-doped bulk samples were optimized, and the Ba-doped Ca2.9Ba0.1Co4O9 system was found to have the highest dimensionless figure of merit ZT0.20 at 973K, which was remarkably higher than that of the un-doped sample.