SnO的歧化反应对SnTe热电性能的优化

doi:10.15541/jim20180288

摘要/Abstract

摘要：

PbTe基化合物是一种热电性能优良的中温区热电材料, 但铅的毒性限制了其广泛应用, 因此类似化合物SnTe引起了人们关注。但SnTe的载流子浓度较高和晶格热导率较大使其ZT值较低。本研究利用SnO歧化反应对SnTe热电性能实现了协同调控。热压烧结过程中SnO在500 ℃左右发生歧化反应生成Sn单质和单分散的SnO₂颗粒, Sn单质作为自掺杂可以填充SnTe中的Sn空位, 导致载流子浓度降低: 相比于SnTe基体, SnTe-6mol%SnO样品在600 ℃下的电阻率从6.5增大到10.5μΩ•m, Seebeck系数从105增大到146μV•K^-1。同时, 原位反应生成的SnO₂第二相单分散于晶界处, 多尺度散射声子传播而降低晶格热导率, SnTe-6mol%SnO样品晶格热导率在600 ℃下仅为0.6W•m^-1•K^-1, 相比于基体下降了33%左右, 从而使SnTe体系的热电性能得到明显提高。最终, 当SnO加入量为6mol%时, 样品在600 ℃下的ZT值~1, 相比于基体提升了一倍左右。

关键词: SnTe, 歧化反应, 热电性能

Abstract:

PbTe-based compositions are considered as excellent thermoelectric materials for the mid-temperature. However, the toxicity of lead limits its wide application. SnTe compounds, an analogue of PbTe, has attracted much attention. However, its ultrahigh carrier concentration and the large lattice thermal conductivity leads to a low ZT value of SnTe. In this work,thethermoelectric performance of SnTe is synergistically enhanced by introduction of Sn and SnO₂ from the disproportionation of SnO in the process of the hot press sintering. On the one hand, Sn can compensate the Sn vacancies and decrease the carrier concentration of SnTe, leading to a simultaneous enhancement on resistivity and the Seebeck coefficient. For instance, compared with the pristine SnTe, resistivity and the Seebeck coefficient increases from 6.5μΩ•m to 10.5μΩ•m and from 105μV•K^-1to 146μV•K^-1,respectively, for the sample of SnTe-6mol% SnO at 873K. On the other hand, in-situ generated SnO₂ nanoparticles are dispersedly distributed on the grain boundaries, leading to the multiscale phonon scattering and the reduced lattice thermal conductivity. The minimum lattice thermal conductivity value is 0.6 W•m^-1•K^-1 for the sample SnTe-6mol% SnO at 873K, which is ~33% reduction compared with that of the pristine SnTe. As a result, the maximum ZT value of 0.96 (~100% enhancement, compared with that of the pristine SnTe) at 873K is achieved for the sample SnTe-6mol% SnO.

Key words: SnTe, disproportionation, thermoelectric performance

中图分类号:

TB34

胡慧珊, 杨君友, 辛集武, 李思慧, 姜庆辉. SnO的歧化反应对SnTe热电性能的优化[J]. 无机材料学报, 2019, 34(3): 315-320.

HU Hui-Shan, YANG Jun-You, XIN Jin-Wu, LI Si-Hui, JIANG Qing-Hui. High Thermoelectric Performance of SnTe from the Disproportionation of SnO[J]. Journal of Inorganic Materials, 2019, 34(3): 315-320.

图/表 8

图1 SnO粉末与热压后样品SnTe-6mol%SnO的DTA曲线, 由DTA曲线可见(图右上角Exo表示放热反应), SnO粉末在725K左右开始发生强烈分解, 并在805K左右达到峰值, 其歧化反应式[21]可表示为:

图1 SnO粉末与热压后样品SnTe-6mol%SnO的DTA曲线

Fig. 1 DTA curves of SnO powder and hot pressed SnTe-6mol%SnO

图2 SnTe-xmol%SnO样品的XRD图谱(a)和高角度峰位置比较(b)

Fig.2 XRD patterns of SnTe-xmol%SnO (x=0, 2, 4, 6)samples(a) and high angle peak position comparison between different samples(b)

图3 SnTe(a)和SnTe-6mol%SnO(b)样品的高倍断口FESEM照片, 图(b)中对应区域的EDS点扫描(c)和样品SnTe-6mol%SnO的低倍断口FESEM照片(d)

Fig.3 High magnification cross-sectional FESEM image of (a) SnTe and (b) SnTe-6mol%SnO sample, (c) EDS composition analysis results for the spot marked in Fig.3(b), low magnification cross-sectional FESEM image of SnTe-6mol%SnO sample (d)

图4 SnTe-ymol%SnO2 (y=0, 1, 2, 3)样品的电阻率(a)和Seebeck系数(b)随温度变化的关系

Fig.4 Temperature dependence of (a) electrical resisitivity and (b) Seebeck coefficient of SnTe-ymol%SnO2 (y=0, 1, 2, 3) samples

图5 SnTe-xmol%SnO样品的电阻率(a), 室温载流子浓度和迁移率(b), Seebeck系数(c)和功率因子(d)随温度变化的关系

Fig.5 Temperature dependence of (a)electrical resisitivity, (b) Seebeck coefficient, (c) power factor of SnTe-xmol%SnO2(x=0, 2,4,6) samples, (d) carrier concentration (n) and carrier mobility (m) at room temperature of the samples

图6 SnTe-xmol%SnO样品的(a)热导率, (b)电子热导率和(c)晶格热导率随温度变化的关系

Fig.6 Temperature dependence of (a) thermal conductivity, (b) carrier thermal conductivity and (c) lattice thermal conductivity of SnTe-xmol%SnO samples

图7 SnTe-xmol%SnO样品的ZT值随温度变化的关系

Fig.7 Temperature dependence of ZT values of SnTe-xmol%SnOsamples

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