Quasi-1D electronic transport and isotropic phonon transport in the Zintl Ca5In2Sb6
Quasi-1D electronic transport and isotropic phonon transport in the Zintl Ca5In2Sb6
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DOI：
10.1016/j.mtphys.2021.100597
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发表时间：
2022-01
影响因子：
11.5
通讯作者：
David M. Smiadak;Romain Claes;Nicolás Pérez;M. Marshall;Wanyue Peng;Wei Chen;G. Hautier;G. Schierning;A. Zevalkink
中科院分区：
文献类型：
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作者：
David M. Smiadak;Romain Claes;Nicolás Pérez;M. Marshall;Wanyue Peng;Wei Chen;G. Hautier;G. Schierning;A. Zevalkink
如果Seebeck系数和热导率相对各向同性，具有各向异性热电输运系数的晶体可以沿着具有最高电子迁移率的方向产生高的品质因数。在本研究中，我们采用实验和理论相结合的方法研究了准一维Zint1相Ca5In2Sb6的各向异性性质。通过从头计算预测，Ca5In2Sb6具有极各向异性的导电性和功率因数，产生于平行于梯形多阴离子链的光有效质量。相反，Seebeck系数和晶格热导率被预测为相对各向同性。后者被近似各向同性的声张量计算速度和实验获得的热膨胀系数所证实。在富In-Sb熔剂中生长了Ca5In2Sb6单晶，并测量了其与聚阴离子链平行和垂直的电导率。由于晶体横截面较小，垂直于生长方向的测量需要一种新的光刻方法，即使用聚焦离子束球磨提取微带，并使用激光光刻来沉积接触以测量电阻率和霍尔系数。平行于生长方向的电导率比垂直方向高近20倍，这与我们的理论预测是一致的。这项研究是第一批实验证实了锌系热电材料的高各向异性电导率之一。
Crystals with anisotropic thermoelectric transport coefficients can yield a high figure-of-merit along the direction with the highest electronic mobility, provided the Seebeck coefficient and thermal conductivity are relatively isotropic. In this study, we combine experiment and theory to investigate the anisotropic properties of the quasi-1D Zintl phase Ca5In2Sb6. Ca5In2Sb6is predicted byab initiocalculations to have extremely anisotropicp-type electrical conductivity and power factor, arising from light effective mass parallel to its ladder-like polyanionic chains. In contrast, the Seebeck coefficient and lattice thermal conductivity are predicted to be relatively isotropic. The latter is evidenced by the nearly isotropic computed speed of sound tensor and experimentally obtained thermal expansion coefficients. In order to characterize the anisotropic electrical conductivity, Ca5In2Sb6single crystals were grown from an In–Sb rich molten flux and measured both parallel and perpendicular to the polyanionic chains. Due to the small crystal cross-sections, measurements perpendicular to the growth direction demanded a novel photolithography methodology whereby micro-ribbons were extracted using focused ion beam milling, and processed using laser photolithography to deposit contacts for electrical resistivity and Hall coefficient measurements. The conductivity parallel to the growth direction was found to be nearly 20x higher than the perpendicular direction, in agreement with our theoretical predictions. This study represents one of the first experimental confirmations of highly anisotropic electrical conductivity in Zintl thermoelectrics.