化学镀对Bi-Te基热电材料性能的影响

发布时间：2018-03-11 10:00

本文选题：热电材料　切入点：化学镀　出处：《合肥工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着环境污染和能源问题的加剧,对热电材料等新型能源转化材料的研究得到广泛关注。Bi-Te基热电材料是室温附近性能最佳的热电材料,但仍存在热电转换效率较低、机械性能较差等问题。本文以n型和p型Bi-Te基热电粉体为基体,采用化学还原沉积法在粉体表面修饰不同种类和含量的金属层,然后烧结成块体试样,探究其对材料的热电及机械性能的影响,具体内容如下:1、探究了表面修饰Ni含量对p型Bi_(0.5)Sb_(1.5)Te_3/Ni块体试样的性能影响。热压和放电等离子烧结Bi_(0.5)Sb_(1.5)Te_3/Ni块体试样的ZT值基本不变或略有下降。但Ni含量较低时,Bi_(0.5)Sb_(1.5)Te_3/Ni块体合金的Seebeck系数大幅度上升,该工作为后续实验提供了思路。2、研究化学镀Cu含量对p型Bi_(0.5)Sb_(1.5)Te_3/Cu块体试样的性能影响。随着Cu含量的增加,试样的载流子浓度上升,载流子迁移率下降。Bi_(0.5)Sb_(1.5)Te_3/Cu试样的电导率明显提高,晶格热导率大幅度下降,热电性能得到改善。同时,随着Cu含量的上升,ZT峰值向高温端偏移。低温区性能最好的试样Cu含量为0.05wt.%,ZT峰值在372K从_(0.5)9提高到1.08。Cu含量增加到0.22wt.%时,ZT峰值移动到高温区域(573K)从0.12提高到0.89。3、基于以上实验结果,采用在Bi_(0.5)Sb_(1.5)Te_3粉末基体表面先镀Ni提高试样的Seebeck系数,再镀Cu同时提高功率因子和降低热导率的方法提高材料的性能。相比于Bi_(0.5)Sb_(1.5)Te_3/Cu试样,Bi_(0.5)Sb_(1.5)Te_3/Ni-Cu试样的功率因子上升,晶格热导率进一步下降。在含有_(0.3)wt.%Ni和0.15wt.%Cu的试样中,ZT峰值在473K从_(0.3)2提高到1.16,材料的热电性能得到进一步提高。4、探究了化学镀Cu含量对n型Bi_2Te_(2.7)Se_(0.3)/Cu块体试样的影响。Bi_2Te_(2.7)Se_(0.3)/Cu试样的Seebeck系数大幅度上升,因而功率因子大幅度上升,说明电传输性能得到明显改善。与Bi_(0.5)Sb_(1.5)Te_3/Cu试样相似,调节Cu含量可以改善试样在不同温度区间的热电性能。高温区性能最好的试样Cu含量为0.05wt.%,ZT峰值在623K从_(0.3)5提高到0.85。Cu含量增加到0.15wt.%时,ZT峰值移动到低温区域(373K)从0.24提高到0.71。同时,无论金属层的种类和含量,所有经过表面修饰的试样的机械性能得到提高。
[Abstract]:With the increasing of environmental pollution and energy problems, the research on new energy conversion materials, such as thermoelectric materials, has received wide attention. Bi-Te based thermoelectric materials are the best thermoelectric materials near room temperature, but there are still low efficiency of thermoelectric conversion. In this paper, n type and p type Bi-Te based thermoelectric powder were used as the matrix, the surface of the powder was modified with different kinds and contents of metal layer by chemical reduction deposition method, and then sintered into bulk sample. To explore its effect on the thermoelectric and mechanical properties of materials, The specific contents are as follows: 1. The effect of surface modified Ni content on the properties of p-type Bi_(0.5)Sb_(1.5)Te_3/Ni bulk samples is investigated. The ZT values of Bi_(0.5)Sb_(1.5)Te_3/Ni bulk samples by hot pressing and Spark plasma sintering are basically unchanged or slightly decreased, but when Ni content is low, there is no significant difference between them. The Seebeck coefficient of gold increased greatly. This work provides ideas for further experiments, and studies the effect of electroless Cu plating on the properties of p-type Bi_(0.5)Sb_(1.5)Te_3/Cu bulk samples. With the increase of Cu content, the carrier concentration of the sample increases, and the carrier mobility decreases. The lattice thermal conductivity is greatly reduced and the thermoelectric properties are improved. With the increase of Cu content, the peak value of ZT shifted to the end of high temperature. The peak value of Cu in the sample with the best properties in the low temperature region was 0.05wt.t. ZT from 372K to 1.08.Cu, which moved from 0.12 to 0.89.3K. based on the above experimental results, the peak value of ZT shifted from 0.12 to 0.89.3K, and the peak value of ZT shifted to the high temperature region from 0.22wt.% to 0.22wt.% at 372K. The Seebeck coefficient of the sample was improved by Ni plating on the surface of the Bi_(0.5)Sb_(1.5)Te_3 powder, then the power factor and the thermal conductivity of the sample were increased by Cu plating. Compared with the Bi_(0.5)Sb_(1.5)Te_3/Cu sample, the power factor of the Bi_(0.5)Sb_(1.5)Te_3/Cu sample was increased. The lattice thermal conductivity decreased further. The peak value of ZT at 473K was increased from 0.3k-2 to 1.16 in the samples containing 0.3wt. Ni and 0.15wt. Cu.The thermoelectric properties of the materials were further improved .4.The effect of electroless Cu plating on n-type Bi_2Te_(2.7)Se_(0.3)/Cu bulk samples was investigated. The Seebeck coefficient of. As a result, the power factor has been greatly increased, which indicates that the electrical transport performance has been improved obviously, which is similar to that of the Bi_(0.5)Sb_(1.5)Te_3/Cu sample. Adjusting Cu content can improve the thermoelectric properties of the samples at different temperatures. The Cu content of the best samples in the high temperature region is 0.05wt.TZ the peak value of ZT increases from 0.3kg to 0.85wt.% at 623K, and the peak value shifts from 0.24 to 0.71K in the low temperature region. The mechanical properties of all surface modified samples were improved regardless of the type and content of the metal layer.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.4

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