Gd掺杂对Ca3Co4O9热电材料的自旋熵影响研究

摘要Ca3Co4O9+δ钴基氧化物是近年来备受关注的氧化物热电材料之一，其具有无毒性，可在高温氧化条件下长期工作、制备简单、成本低等优点。自旋熵被认为在提高钴基氧化物热电材料热电势中起着重要作用，是大热电势的来源。本论文以Ca3Co4O9+δ为研究对象，用磁热电势的方法研究了Gd掺杂对其自旋熵的影响和规律，并对自旋熵的调控进行研究。

用溶胶凝胶法制备Ca3-xGdxCo4O9+δ系列样本，通过磁热电势发现磁场能够抑制热电势，抑制效应随着Gd掺杂的增加而加大，揭示了Gd掺杂能够提高Ca3Co4O9+δ的自旋熵。通过X射线光电子能谱（XPS）的结果确定了Gd掺杂会引起Co4+离子浓度的减少。因此，通过以上结果研究我们认为可以通过抑制钴基氧化物中的Co4+离子的浓度来调控自旋熵。67241

毕业论文关键词：热电性能；钴基氧化物；自旋熵。

毕业设计说明书（论文）外文摘要

Title Study of the effects of Gd doping on the spin entropy

in the thermoelectric material of Ca3Co4O9

Abstract

Recently, people pay more attention to Ca3Co4O9+δ based thermoelectric oxides due to their thermal stability, anti-oxidation and pollution-free. It is considered that the spin entropy plays an important role in enhancing the thermopower in cobalt oxides and is the source for the observed large thermopower. In this dissertation,we devote our attention to Ca3Co4O9+δ. We study the doping effects of Gd on the spin entropy of Ca3Co4O9+δ by magnetothermopower and study on the regulation and control of spin entropy.

A series of Ca3-xGdxCo4O9+δ has been prepared by sol-gel method. Magnetothermopower is found the magnetic-field can suppress the thermoelectric potential and the suppressing effect increases up on Gd doping, revealing that Gd doping can improve the spin entropy of Ca3Co4O9+δ. By the result of X-ray photoemission spectroscopy (XPS), we can determine the decrease of Co4+ concentration induced by Gd doping. These results suggest us that we can improve the spin entropy by suppressing Co4+ concentration in cobalt oxides.

Keywords：Thermoelectric properties;Cobalt oxide;Spin entropy.

第一章绪论 1

1.1 引言 1

1.2 热电效应 1

1.2.1 Seebeck效应 2

1.2.2 Peltier效应 3

1.2.3 Thomson效应 4

1.2.4 热电效应的应用 4

1.3 热电材料的发展 6

1.3.1 Ca3Co4O9+体系热电材料 7

1.3.2 热电材料自旋熵的研究现状 8

1.4 本课题的研究目的和意义 9

第二章实验方法 10

2.1 溶胶-凝胶法制备材料 10

2.2 X射线衍射分析 10

2.3 热电势测量 10

2.4 自旋熵作用的研究 10

2.5 X射线吸收谱分析 11

第三章 Gd掺杂对Ca3Co4O9+δ的热电性能及自旋熵的影响 Gd掺杂对Ca3Co4O9热电材料的自旋熵影响研究:http://www.751com.cn/cailiao/lunwen_75365.html