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Graphene boosts thermoelectric performance of a Zintl phase compound

机译：石墨烯提高Zintl相化合物的热电性能

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The concept of nanocomposites derived by incorporating a second minor phase in bulk thermoelectric materials has established itself as an effective paradigm for optimizing high thermoelectric performance. In this work, this paradigm is for the first time extended to bulk Zintl phase Mg3Sb2 and its isoelectronically Bi-doped derivative Mg3Sb1.8Bi0.2 system. Herein, we report the synthesis, microstructural details, electronic structure and thermoelectric properties of (Mg3Sb2, Mg3Sb1.8Bi0.2)/ graphene nanosheet (GNS) nanocomposites with different mass ratios. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) investigation reveals that Mg3Sb2 nanoparticles are homogenously anchored on the surface of GNS. We demonstrate that Mg3Sb2-based materials incorporated with a small content of graphene outperform optimally, resulting in potential p-type thermoelectric materials. The present nanocomposite additive of GNS deriving such a novel nanocomposite of (Mg3Sb2, Mg3Sb1.8Bi0.2)/GNS, enhances the electrical conductivity significantly, thereby resulting in a substantially large increase in the power factor. The enhanced electrical conductivity of these nanocomposites is attributed to the increase in the carrier concentration and high carrier mobility owing to the ultra high mobility of graphene. X-ray photoelectron spectroscopy (XPS) core level spectra confirm weak bonding between GNS and Mg3Sb2. Increase in carrier concentration is reflected in XPS valence band spectra and change in spectral weight near valence band maxima is indicative of increased electrical conductivity in the nanocomposite material. The thermal conductivity of these nanocomposites is noted to be reduced at high temperature. These favorable conditions lead to enhanced thermoelectric figure-of-merit (ZT) = 0.71 at 773 K for Mg3Sb2/GNS and a ZT = 1.35 at 773 K for Mg3Sb1.8Bi0.2/GNS nanocomposites with the mass ratio of 80 : 1 which are similar to 170% and similar to 125% higher values compared to bare Mg3Sb2 and bare Mg3Sb1.8Bi0.2 respectively. We strongly believe that the present novel strategy of fabricating such a nanocomposite of a Zintl compound by utilizing GNS as a nanocomposite additive, may provide an emerging path for improving thermoelectric properties of various Zintl phase compounds.
机译：通过在本体热电材料中掺入第二次要相而衍生的纳米复合材料的概念已确立其自身为优化高热电性能的有效范例。在这项工作中，该范例首次扩展到整体Zintl相Mg3Sb2及其等电双掺杂的衍生物Mg3Sb1.8Bi0.2系统。在此，我们报告了不同质量比的（Mg3Sb2，Mg3Sb1.8Bi0.2）/石墨烯纳米片（GNS）纳米复合材料的合成，微观结构，电子结构和热电性能。场发射扫描电子显微镜（FE-SEM）和透射电子显微镜（TEM）研究表明，Mg3Sb2纳米颗粒均匀地锚定在GNS的表面上。我们证明掺入少量石墨烯的基于Mg3Sb2的材料的性能最佳，从而导致潜在的p型热电材料。衍生出这种新型的（Mg3Sb2，Mg3Sb1.8Bi0.2）/ GNS纳米复合材料的GNS纳米复合添加剂可以显着提高电导率，从而大大提高功率因数。这些纳米复合材料的电导率提高归因于由于石墨烯的超高迁移率而导致的载流子浓度增加和高载流子迁移率。 X射线光电子能谱（XPS）核心能级谱证实了GNS与Mg3Sb2之间的键合较弱。载流子浓度的增加反映在XPS价带谱中，并且在价带最大值附近的谱重变化表明纳米复合材料的电导率增加。这些纳米复合材料的热导率在高温下会降低。这些有利条件导致Mg3Sb2 / GNS在773 K时热电品质因数（ZT）= 0.71，Mg3Sb1.8Bi0.2 / GNS纳米复合材料在773 K时ZT = 1.35，质量比为80：1，其中分别比裸Mg3Sb2和裸Mg3Sb1.8Bi0.2高170％和高125％。我们坚信，通过利用GNS作为纳米复合添加剂来制造Zintl化合物的这种纳米复合材料的新策略，可以为改善各种Zintl相化合物的热电性能提供一条新兴途径。

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