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Grain boundary dominated charge transport in Mg3Sb2-based compounds†
Energy & Environmental Science ( IF 32.4 ) Pub Date : 2018-01-19 00:00:00 , DOI: 10.1039/c7ee03326e Jimmy Jiahong Kuo 1, 2, 3 , Stephen Dongmin Kang 1, 2, 3, 4, 5 , Kazuki Imasato 1, 2, 3 , Hiromasa Tamaki 6, 7, 8 , Saneyuki Ohno 1, 2, 3, 4, 5 , Tsutomu Kanno 6, 7, 8 , G. Jeffrey Snyder 1, 2, 3
Energy & Environmental Science ( IF 32.4 ) Pub Date : 2018-01-19 00:00:00 , DOI: 10.1039/c7ee03326e Jimmy Jiahong Kuo 1, 2, 3 , Stephen Dongmin Kang 1, 2, 3, 4, 5 , Kazuki Imasato 1, 2, 3 , Hiromasa Tamaki 6, 7, 8 , Saneyuki Ohno 1, 2, 3, 4, 5 , Tsutomu Kanno 6, 7, 8 , G. Jeffrey Snyder 1, 2, 3
Affiliation
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Thermally activated mobility near room temperature is a signature of detrimental scattering that limits the efficiency and figure-of-merit zT in thermoelectric semiconductors. This effect has been observed dramatically in Mg3Sb2-based compounds, but also to a lesser extent in other thermoelectric compounds. Processing samples differently or adding impurities such that this effect is less noticeable produces materials with a higher zT. Experiments suggest that the behavior is related to grain boundaries, but impurity scattering has also been proposed. However, conventional models using Matthissen's rule are not able to explain the dramatic change in the temperature dependency of conductivity or drift mobility which is observed in Mg3Sb2-based compounds. We find that it is essential to consider the grain boundary region as an effectively separate phase rather than a scattering center, taking into account the weaker screening in semiconductors compared with classical metals. By modeling a grain boundary phase with a band offset, we successfully reproduce the experimentally observed conductivity versus temperature and thermopower versus conductivity relations, which indicate an improved description of transport. The model shows good agreement with measured grain size dependencies of conductivity, opening up avenues for quantitatively engineering materials with similar behavior. Model estimates predict room for >60% improvement in the room temperature zT of Mg3.2Sb1.5Bi0.49Te0.01 if the grain boundary resistance could be eliminated.
中文翻译：
基于 Mg 3 Sb 2的化合物中晶界占主导的电荷传输†
室温附近的热活化迁移率是有害散射的标志，有害散射限制了热电半导体的效率和品质因数zT。在基于Mg 3 Sb 2的化合物中已显着观察到了这种作用，但在其他热电化合物中也观察到了较小程度的作用。以不同方式处理样品或添加杂质，以使这种影响不太明显，会产生具有较高zT的材料。实验表明，该行为与晶界有关，但也提出了杂质散射的建议。但是，使用Matthissen规则的常规模型无法解释以Mg观察到的电导率或漂移迁移率的温度依赖性的急剧变化。3 Sb 2基化合物。我们发现，考虑到半导体与传统金属相比的较弱筛选，必须将晶界区域视为有效的分离相而不是散射中心。通过对带隙偏移的晶界相进行建模，我们成功地再现了实验观察到的电导率与温度之间的关系以及热电势与电导率之间的关系，这表明对输运的描述有所改善。该模型显示出与测量的电导率的晶粒大小相关性良好的一致性，为具有相似行为的定量工程材料打开了途径。模型估计预测房间的室温zT改善> 60％Mg 3.2 Sb 1.5 Bi 0.49 Te 0.01可以消除晶界电阻。
更新日期：2018-01-19
中文翻译：
基于 Mg 3 Sb 2的化合物中晶界占主导的电荷传输†
室温附近的热活化迁移率是有害散射的标志，有害散射限制了热电半导体的效率和品质因数zT。在基于Mg 3 Sb 2的化合物中已显着观察到了这种作用，但在其他热电化合物中也观察到了较小程度的作用。以不同方式处理样品或添加杂质，以使这种影响不太明显，会产生具有较高zT的材料。实验表明，该行为与晶界有关，但也提出了杂质散射的建议。但是，使用Matthissen规则的常规模型无法解释以Mg观察到的电导率或漂移迁移率的温度依赖性的急剧变化。3 Sb 2基化合物。我们发现，考虑到半导体与传统金属相比的较弱筛选，必须将晶界区域视为有效的分离相而不是散射中心。通过对带隙偏移的晶界相进行建模，我们成功地再现了实验观察到的电导率与温度之间的关系以及热电势与电导率之间的关系，这表明对输运的描述有所改善。该模型显示出与测量的电导率的晶粒大小相关性良好的一致性，为具有相似行为的定量工程材料打开了途径。模型估计预测房间的室温zT改善> 60％Mg 3.2 Sb 1.5 Bi 0.49 Te 0.01可以消除晶界电阻。
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