氩气气氛下掺杂FeSe超导体的制备和性能研究

论文总字数：21189字

摘 要

高温超导材料中，它们的超导转变温度距离应用还有一些差距。相对来说，Cu基超导体的发展还比较完善，而Fe基超导体的超导转变温度仍然需要进一步提高。而且有关超导的物理机理还没有定论，这也需要做进一步的研究。特别是它的超导转变温度稍稍高于BCS理论的极限，这就使得它更加具有理论研究价值。现在，按照母体化合物的组成和晶体结构来分类，铁基超导体包括铁硒超导体和铁砷超导体。铁基超导材料中，由于FeSe超导体实验装置简单、没有砷这个剧毒元素、安全性高而引起了科研人员的高度重视。可是该类超导体的制备条件通常较为苛刻，需要高压机封管技术，使其在推广和应用方面面临着非常大的困难。

因此，本文主要研究通过氩气气氛下的制备技术，制备出Fe基超导材料，并研究其超导性能的变化。晶体样品主要是用X射线衍射分析确定为超导四方相。把Ge添加到FeSe_0.5Te_0.5的样品中是通过两步固相反应路线合成的。我们发现了在FeSe_0.5Te_0.5样品的烧结过程中，锗的添加可以显著增强样品从六方相向超导四方相的转变。随着超导相比例的增加和结晶度的改善，添加5％的Ge显著地将超导转变温度（Tc）提高了3K。通过电子传输和抗磁性测量，可看出超导转变温度在大约10 K的温度下。

关键词：氩气气氛,FeSe,铁基超导体,元素掺杂

Abstract

In high-temperature superconducting materials, there is still so-me gap between their superconducting transition temperatures and applications. Relatively speaking, the development of Cu-based superconductors is relatively complete, and the superconducting transition temperature of Fe-based superconductors still needs to be further improved. Moreover, the physical mechanism of superconductivity has not yet been finalized. This requires further research. In particular, its superconducting transition temperature is slightly higher than the limit of BCS theory, which makes it more theoretically valuable. Now, iron-based superconductors can be classified into iron arsenic superconductors and iron selenide superconductors, based on the composition of the parent compound and the crystal structure classification. In the iron-based superconducting materials, the FeSe superconductor experimental apparatus is simple, there is no such a poisonous element of arsenic, and the use is safer, which is much favored by scientific researchers. However, the prepration conditions of this type of superconductor are generally severe, and high-pressure machine sealing technology is required, which poses great difficulties in promotion and application.

Therefore, this article mainly studies the preparation of Fe-based superconducting materials by the preparation of argon atmosphere, and studies the changes of superconducting properties. The crystal sample was mainly determined as a superconducting tetragonal phase by X-ray diffraction analysis. Adding Ge to the sample of FeSe_0.5Te_0.5 was synthesized by a two-step solid-phase reaction route. We found that during the sintering of FeSe_0.5Te_0.5 samples, the addition of niobium can significantly enhance the transformation of the sample from the hexagonal phase to the superconducting tetragonal phase. With the increase of superconductivity and the improvement of crystallinity, the addition of 5% Ge significantly increases the superconducting transition temperature (Tc) by 3K. From electron transport and diamagnetic measurements, it can be seen that the superconducting transition temperature is at a temperature of about 10 K.

KEY WORDS: Argon atmosphere, FeSe, Iron-based superconductors, Element doping

目 录

摘要 I

Abstract II

第一章 绪论 1

1.1 前言 1

1.2 高温超导体的定义 1

1.3 高温超导体的发展历程 2

1.4 高温超导体的分类 2

1.5 高温超导体的应用 3

1.6 高温超导体的发展前景 4

第二章 常用的制备高温超导体的方法 6

2.1 固相反应法 6

2.1.1 固相反应法的定义 6

2.1.2 固相反应法的分类 6

2.1.3 固相反应法的原理 6

2.1.4 固相反应法的工艺特点 6

2.1.5 固相反应法的优缺点 7

2.2 助熔剂法 7

2.2.1 助熔剂法的定义 7

2.2.2 助熔剂法的原理 7

2.2.3 助熔剂法的分类 8

2.2.4 助熔剂法的特点 9

2.2.5 助熔剂法的应用 9

2.2.6 助熔剂法的优缺点 10

2.2.7 准确地选取理想的助熔剂 10

第三章 氩气气氛下掺杂FeSe超导体的制备和性能研究 12

3.1 引言 12

3.2 实验过程 12

3.3 形貌分析 14

3.4 X射线衍射图谱分析 18

3.5 超导性能测试研究 20

3.6 结论 21

致谢 23

参考文献 24

1. 绪论

1.1前言

当今社会，我们在享用现代文明的同时，同样遭遇着局势日益严峻的能源、资源紧缺的问题。当前是一个大数据的时代，人们却仍然仰仗着之前设计的各个电力系统，仅有的变化是所拉的电缆越来越粗、使用的机组越变越大。目前，能源的供应已经变得越来越紧张；更残酷的是输送过程中非常多的电能却被白白地损耗在所使用的传统材料上。现在，我国电网的总发电量的12%电能被损耗了,其中超过九成是由输送电缆损耗的。到2013年，据估测，中国在输配电网上耗费了2到3个三峡电站的发电量。这表明，我国每年损失的电量高达几千亿度，二氧化碳排放量将以亿吨计。而美国每年单单是在输送电缆上的经济损失就高达数十亿美元。但是如果使用高温超导线材，就可以有以下3点好处：1、可以避免大量金钱损失；2、节省非常多的金属材料；3、更重要的是，有利于我国生态文明建设的鼎力发展，在世界控制碳排放值方面占得先机。为我国将来的节能减排计划打下坚实的根基，而且能够更好地实行我国的可持续发展战略。

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