Anisotropic correlations in higher manganese silicides
Anisotropic correlations in higher manganese silicides
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高锰硅化物中的各向异性相关性
DOI：
10.1016/j.jallcom.2022.167983
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发表时间：
2023
影响因子：
6.2
通讯作者：
Miyazaki Yuzuru
中科院分区：
文献类型：
--
作者：
Chauhan Nagendra S.;Ono Ichiro;Hayashi Kei;Miyazaki Yuzuru
各向异性相关性对于理解高锰硅化物 (HMS) 的热电输运特性至关重要。在这项工作中，我们通过检查熔融生长单晶的取向变化和放电等离子体烧结的 HMS 多晶样品的定向结构，确定了各向异性对热电性能的影响。垂直于 c 轴（即沿解理面）排列的单晶样品表现出高导电性和导热性，而最大塞贝克系数是沿 c 轴方向测量的。同样，与单晶样品相比，多晶样品表现出减弱的各向异性、增强的加权迁移率和降低的热导率，从而导致相对较高的热电品质因数（zT）。研究发现，在熔融生长的单晶中，特征性 MnSi 条纹主要垂直于 c 轴生长，而在烧结多晶中通常观察到烧结过程中的包晶分解，从而在合成的 HMS 晶体中产生固有的无序和调制晶格结构。据观察，如果在不同方向测量电荷和声子传输特性，则可能会错误地估计单晶和多晶 HMS 的 zT。这项研究为 HMS 的结构-性能关系提供了新的见解，并表明在解决 HMS 晶体中普遍存在的各向异性行为和微观结构演变时需要更仔细的考虑。
Anisotropic correlations are vital for understanding the thermoelectric transport properties of higher manganese silicides (HMSs). In this work, we establish the implications of anisotropy on thermoelectric performance by examining the orientational variants in melt-grown single crystal and directional configurations of spark plasma sintered polycrystalline specimens of HMS. Single crystal specimen aligned perpendicular to thec-axis (i.e., along the cleavageab-plane) exhibited high electrical and thermal conductivity, while the maximum Seebeck coefficient was measured along thec-axis direction. Similarly, polycrystalline specimens exhibited a weakened anisotropy with an enhanced weighted mobility and reduced thermal conductivity than their monocrystal counterpart resulting in a relatively higher thermoelectric figure-of-merit (zT). The characteristic MnSi striations were found to be predominantly grown perpendicular to thec-axis in melt-grown single crystals while peritectic decomposition during sintering is commonly observed in sintered polycrystals thereby emanating an inherently disordered and modulated lattice structure in the synthesized HMS crystals. It was observed that thezTfor single and polycrystalline HMSs could be erroneously estimated if charge and phonon transport properties are measured in different directions. This study offers newer insights into the structure-property relationships of HMSs and demonstrates the need for more careful considerations in addressing the anisotropic behavior and microstructural evolutions that prevails in HMS crystals.