【热电材料专题】Ge基笼状化合物
高温高压制备
Thermoelectric properties of In-substituted Ge-based clathrates prepared by HPHT
通过高压高温法制备的In取代Ge基笼型化合物的热电性能
Authors: Binwu Liu, Hongan Ma*, Dexuan Huo, Haiqiang Liu, Baomin Liu, Jiaxiang Chen and Xiaopeng Jia*
Volume 4, Issue 1, Pages 68-74
Bulk materials Ba8Ga16InxGe30-x (x = 0.5, 1.0, 1.5) were prepared by High-Pressure and High-Temperature (HPHT) method and the crystal structure has been confirmed by X-ray diffraction and cell refinement.
本实验通过高压高温（HPHT）法制备了块体材料Ba8Ga16InxGe30-x（x= 0.5,1.0,1.5），并通过X射线衍射和晶胞修正证实了其晶体结构。
The actual In composition was much lower than the starting composition, and lattice constants increased with the increase of substitution.
实际获得的样品中的In含量远小于初期含量，并且晶格常数随着In取代量的增加而增加。
As the temperature increased, the Seebeck coefficient and electrical resistivity increased first and then decreased, while the thermal conductivity was the opposite, which leads to significant enhancement on thermoelectric properties of the clathrates.
随着温度的升高，塞贝克系数和电阻率先增大后减小，而热导率则相反，这导致了此笼型化合物的热电性能得到了显著提升。
The substitution of indium elements decreased the seebeck coefficient and electrical resistivity, and also changed the microstructure of the compounds.
铟元素的取代降低了塞贝克系数和电阻率，同时也改变了化合物的微观结构。
A minimum thermal conductivity of 0.84 Wm−1K−1 was obtained, and a good ZT value of 0.52 was achieved.
最终实验获得了0.84 Wm−1K−1的最低热导率以及0.52的ZT值。
The grain boundaries and lattice defects generated by high pressure can effectively scatter phonons of different frequencies, which reduce the lattice thermal conductivity.
高压产生的晶界和晶格缺陷可以有效地散射不同频率的声子，从而降低晶格热导率。
文中部分图片：
晶体结构
Fig. 2. XRD patterns of Ba8Ga16InxGe30-x samples prepared by HPHT.
温度对Seeback系数、电阻、热导率和晶格热导率的影响
Fig. 3. Temperature dependence of (a) Seebeck coefficient (b) Electrical resistivity (c) Thermal conductivity (d) Lattice thermal conductivity for Ba8Ga16InxGe30-x prepared by HPHT.
微观形貌
Fig. 4. SEM micrographs of (a, b) Ba8Ga16In0.5Ge29.5; (c, d) Ba8Ga16In1.0Ge29 and (e, f) Ba8Ga16In1.5Ge28.5 prepared by HPHT method.
不同晶格取向
Fig. 5. HRTEM images of the (a, b) Ba8Ga16In1.0Ge29; (c, d) Ba8Ga16In1.5Ge28.5. The A region shows different lattice orientation; the B region represents the lattice curvatures and dislocation; the C region is the amorphous region; the D region mark the black and white stripes.
zT优值和温度的关系
Fig. 6. Temperature dependence of the dimensionless figure of merit, ZT, of Ba8Ga16InxGe30-x.
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想知道这篇妙文的第一作者是谁吗？他就是来自吉林大学超硬材料国家重点实验室的Binwu Liu！
Binwu Liu is a graduate student in National Key Lab of Superhard Materials at Jilin University. My researches focus on the synthesis and performance optimization of thermoelectric materials (I-type Clathrates) by high pressure and high temperature method.
局域震荡和笼状畸变
Germanium isotope effect induced guest rattling and cage distortion in clathrates
锗同位素效应引起的络合物中客体原子局域震荡和笼状畸变
Authors: Ran Ang, Zhengshang Wang, Shang-Fei Wu, Pierre Richard, Zhenzhong Yang, Lin Gu, Gang Mu, Jingtao Xu, Ning Liu, Jun Tang
Volume 4, Issue 4, Pages 338-344
Intermetallic clathrates are materials characterized by a large cage structure where guest atoms can move anharmonically, providing these materials exotic thermoelectric properties.
金属间笼型化合物是一类具有笼状结构、客体原子可以非简谐运动的化合物，这些特征为这类材料提供了独特的热电性能。
Unfortunately, the dynamical and atomic nature of the rattling phonons, and their interactions with the electronic structure, are not fully understood.
然而，局域震荡声子的动力学和原子本质以及他们与电子结构之间的相互作用尚未完全得到理解。
Here, we report that a germanium isotope effect can trigger an inherent guest rattling and cage distortion in clathrate Ba8Ga16Ge30 (BGG).
在本文中，我们报道了锗的同位素效应可以触发笼型化合物Ba8Ga16Ge30（BGG）中的本征客体原子的局域震荡以及笼结构的变形。
Raman-scattering spectroscopy and advanced electron microscopy demonstrate that the atomic germanium isotope effect induces an off-centre rattling at the 6dsites as well as a tetrakaidecahedron deformation which is anisotropic for n-type BGG but isotropic for p-type BGG.
拉曼散射光谱和先进的电子显微镜分析表明了原子级的锗同位素效应引起了在6d位置处的偏心局域震荡以及十四面体的变形，这种变形对于n型BGG是各向异性的，但是对于p型BGG是各向同性的。
The present findings indicate that the large n-type germanium isotope effect arises from the strong electron-phonon coupling, which opens up a novel avenue for manipulating dynamical motions of phonons via atomic isotope engineering.
目前的研究表明，大的n型锗同位素效应源于强的电子-声子耦合，这为通过原子同位素工程操纵声子的动力学运动开辟了一条新途径。
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https://www.sciencedirect.com/science/article/pii/S2352847818300856#!
欣赏了这么有深度的好文章，想不想认识下2位主要的创造者呀？他们就是来自四川大学核科学与工程技术学院的Ran Ang教授和唐军研究员。
Ran Ang is a full professor in Sichuan University, China. He received a Ph.D. from the Institute of Solid State Physics, Chinese Academy of Sciences, and postdoctoral research experience of 7 years from Nanyang Technological University, National University of Singapore, Tohoku University, and National Institute for Materials Science, Japan. He has been working on thermoelectric materials, superconducting materials, and magnetic materials for more than 15 years. His interests are focused on materials physics and thermoelectric applications.
Jun Tang is a full professor in Sichuan University, China. He obtained his Ph.D degree from Institute of High Energy Physics, Chinese Academy of Science in 2006. He was an associate professor of Tohoku University from 2006 to 2011. He has been a faculty member in Sichuan University since 2011. His current research is on the advanced fabrication and materials physics of high efficiency thermoelectric materials and devices.
最后再向大家介绍一下我们闪亮亮的JMAT期刊。它的全称是Journal of Materiomics，是由中国硅酸盐学会和Elsevier合作出版的英文期刊,现已在ScienceDirect上发布了第五卷第一期（2019年），点击文末“阅读全文“可自由获取所有论文全文。
Journal of Materiomics 为同行评议期刊,被web of science和scopus收录，截至目前，最新cite score为7.89，从投稿到在线出版一般只需60天，并且对作者免收发表费！ 投稿说明详见https://www.journals.elsevier.com/journal-of-materiomics/, 期望大家不吝赐稿
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