P-型PbTe基合金的制备与热电性能研究

发布时间：2018-01-09 11:39

本文关键词：P-型PbTe基合金的制备与热电性能研究　出处：《浙江大学》2015年硕士论文　论文类型：学位论文

更多相关文章： 热电材料 PbTe 合金化 能带调整

【摘要】：铅的硫族化合物PbX (X=Te、Se、S)具有相似的晶体结构和能带结构,也是目前性能最好的中温区热电材料,具有结构简单、容易制备以及稳定性好等特点,近年来受到广泛关注。但目前的研究大多针对伪二元合金体系,而且高性能都是从小块试样中获得,很少有人制备大块试样重现高性能并研究其分布规律。针对这些问题,本文选取了合适的伪二元基体进行掺杂优化,分别在Pb位进行Mg取代和在Te位进行Se和S取代,并制备了～200g试样,取得如下主要成果：1.选取伪二元PbTe0.8Se0.2合金作为基体,进行不同Na含量掺杂来研究载流子浓度对材料热电性能影响,发现优化载流子浓度可以有效降低高温下的本征激发对热导率的贡献以及抑制少子对Seebeck系数的不利影响,并确定其最优掺杂浓度为2%Na,试样zT在800K可以达到～1.7。2.对最优掺杂的PbTe0.8Se0.2固溶体进行Mg合金化,研究Mg合金化在降低热导率和能带调整方面的作用。研究发现Mg可以有效的降低PbTe0.8Se0.2合金的晶格热导率,部分试样在800K时接近理论最低热导率；Mg合金化会降低低温范围的电导率,但在600K以上电导率相差不大；Mg合金化增大了禁带宽度,可以有效抑制本征激发,获得较高的Seebeck系数。在Mg含量为6%和8%时,其zT在800K可以达到～2.2。3.在小块Mg合金化的试样获得高性能的同时尝试制备了～200g的大块试样,通过测试表征发现：不论在径向还是轴向,热电性能分布没有明显差别,在同一截面的边缘和内部也没有明显区别。大块试样zT在800K可以达到1.7-2.2。4.在最优掺杂的PbTe0.8Se0.2固溶体基础下进行PbS合金化,研究了在固定PbSe含量为20%,改变PbTe和PbS比例时材料热电性能发现PbS对于热电性能影响不大,所有试样zT在800K可以达到1.7～1.8；随后对伪三元合金PbTe0.7Se0.2S0.1进行Mg合金化,研究发现Mg对试样热电性能影响也不显著；固定PbTe含量为80%,改变PbSe和PbS比例,研究发现改变Se和S的比例对试样的热导率影响不大；PbS的含量大于10%时的试样在600K以上,电导率和Seebeck系数都会出现一个平台,zT可以显著提高,在800K可以达到～2.0左右。
[Abstract]:Lead chalcogenide PbX (X=Te, Se, S) has similar crystal structure and band structure, is currently the performance in temperature region the best thermoelectric material, has the advantages of simple structure, easy fabrication and good stability, attracted wide attention in recent years. But most of the current two yuan for pseudo alloy system moreover, high performance is obtained from the small sample, few people prepare bulk samples to reproduce high performance and study the distribution. To solve these problems, this paper selects the appropriate pseudo two yuan matrix optimizing doping, respectively Mg and Te in the generation of Se site and S substituted at the Pb position, and preparation of ~ 200g samples, the main achievements are as follows: 1.. The selection of pseudo two yuan PbTe0.8Se0.2 alloy as the matrix, doped with different content of Na to study the influence of carrier concentration on the thermoelectric properties of materials, it was found that the optimized carrier concentration can effectively reduce the high temperature Under the excitation of the intrinsic thermal conductivity contribution and inhibition of less adverse effects on Seebeck sub coefficient, and determine the optimal doping concentration is 2%Na, zT ~ 800K in the sample can reach 1.7.2. on the optimal doped PbTe0.8Se0.2 solid solution of Mg alloy, Mg alloy research in reducing the thermal conductivity and the effect of energy band the study found that Mg can effectively reduce the lattice thermal conductivity of PbTe0.8Se0.2 alloys was the most part of the sample is close to the theoretical thermal conductivity in 800K; Mg alloy will decrease the conductivity of the low temperature range, but little difference in conductivity above 600K; Mg alloy increases the width of band gap, can effectively inhibit the intrinsic excitation. Seebeck coefficient is higher. The content of Mg is 6% and 8%, the zT can reach to 800K in 2.2.3. in the sample piece of Mg alloying to obtain high performance at the same time try to bulk sample preparation to 200g, through the test Characterization shows that no matter in the radial or axial direction, there was no significant difference between thermoelectric properties distribution, there were also no significant differences in the same section of the edge and interior. Large specimens of zT can reach 1.7-2.2.4. in the optimal doping of PbTe0.8Se0.2 PbS alloy solid solution based on 800K, the research on the fixed PbSe content is 20%, PbTe when the proportion of PbS and PbS found that the thermoelectric properties of materials for thermoelectric properties have little effect, all specimens of zT in 800K can reach 1.7 ~ 1.8; followed by Mg alloying on pseudo alloy PbTe0.7Se0.2S0.1 three yuan, the study found that the effect of Mg on the thermoelectric properties of samples was not significant; PbTe content is 80%, PbSe and PbS ratio, the study found the change of Se and the ratio of S thermal conductivity of specimen has little effect; the content of PbS is greater than 10% of the samples above 600K, electrical conductivity and Seebeck coefficient will be the emergence of a platform, zT can significantly The improvement can reach about 2 in 800K.

【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB34

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