Thermoelectric transport of semiconductor full-Heusler VFe2Al,Journal of Materials Chemistry C

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Thermoelectric transport of semiconductor full-Heusler VFe2Al
Journal of Materials Chemistry C ( IF 5.7 ) Pub Date : 2020-07-15 , DOI: 10.1039/d0tc02659j
Shashwat Anand _{1,

2,

3,

4} , Ramya Gurunathan _{1,

2,

3,

4} , Thomas Soldi _{1,

2,

3,

4} , Leah Borgsmiller _{1,

2,

3,

4} , Rachel Orenstein _{1,

2,

3,

4} , G. Jeffrey Snyder _{1,

2,

3,

4}

Affiliation

The full-Heusler VFe₂Al has emerged as an important thermoelectric material in its thin film and bulk phases. VFe₂Al is attractive for use as a thermoelectric materials because of it contains only low-cost, non-toxic and earth abundant elements. While VFe₂Al has often been described as a semimetal, here we show the electronic and thermal properties of VFe₂Al can be explained by considering VFe₂Al as a valence precise semiconductor like many other thermoelectric materials but with a very small band gap (E_g = 0.03 ± 0.01 eV). Using a two-band model for electrical transport and point-defect scattering model for thermal transport we analyze the thermoelectric properties of bulk full-Heusler VFe₂Al. We demonstrate that a semiconductor transport model can explain the compilation of data from a variety of n and p-type VFe₂Al compositions assuming a small band-gap between 0.02 eV and 0.04 eV. In this small E_g semiconductor understanding, the model suggests that nominally undoped VFe₂Al samples appear metallic because of intrinsic defects of the order of ∼10²⁰ defects per cm⁻³. We rationalize the observed trends in weighted mobilities (μ_w) with dopant atoms from a molecular orbital understanding of the electronic structure. We use a phonon-point-defect scattering model to understand the dopant-concentration (and, therefore, the carrier-concentration) dependence of thermal conductivity. The electrical and thermal models developed allow us to predict the zT versus carrier concentration curve for this material, which maps well to reported experimental investigations.

中文翻译：

半导体全Heusler VFe2Al的热电传输

全Heusler VFe ₂ Al在其薄膜和体相中已成为一种重要的热电材料。VFe ₂ Al仅包含低成本，无毒且富含地球的元素，因此非常适合用作热电材料。尽管VFe ₂ Al通常被描述为半金属，但在这里我们展示了VFe ₂ Al的电子和热学性质可以通过将VFe ₂ Al视为价电子精密半导体来解释，这与许多其他热电材料一样，但是带隙很小（Ë _{g ^}= 0.03±0.01 eV）。使用两带电传输模型和点缺陷散射模型进行热传输，我们分析了块状全Heusler VFe ₂ Al的热电性能。我们证明，假设在0.02 eV和0.04 eV之间的小带隙，半导体传输模型可以解释各种n和p型VFe ₂ Al成分的数据汇编。根据对E _g半导体的这种小理解，该模型表明，名义上未掺杂的VFe ₂ Al样品由于固有缺陷约为每厘米^-3约^{10 20个}缺陷而显得具有金属性。我们理顺加权迁移率观察到的趋势（μ _{w ^}）的原子从对电子结构的分子轨道理解中获得。我们使用声子点缺陷散射模型来了解热导率对掺杂剂浓度（以及载流子浓度）的依赖性。开发的电学模型和热学模型使我们能够预测这种材料的zT与载流子浓度曲线，该曲线与已报道的实验研究相吻合。

更新日期：2020-08-06

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