Relationship between composition and charge carrier concentration in Eu8Ga16-xGe30+x clathrates
Relationship between composition and charge carrier concentration in Eu8Ga16-xGe30+x clathrates
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DOI：
10.1103/physrevb.71.165205
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发表时间：
2005-04
影响因子：
3.7
通讯作者：
V. Pacheco;A. Bentien;W. Carrillo‐Cabrera;S. Paschen;F. Steglich;Y. Grin
中科院分区：
文献类型：
--
作者：
V. Pacheco;A. Bentien;W. Carrillo‐Cabrera;S. Paschen;F. Steglich;Y. Grin
电荷载流子浓度是寻找适合热电应用的金属间化合物的重要参数。这项工作揭示的影响的确切组成上的电荷载流子浓度。对具有初始成分的试样进行两种不同的热处理。熔体缓慢冷却和随后的退火产生具有笼形I结构（空间群）的相。相比之下，从1040 °C淬火然后退火的样品显示笼形物-VIII结构（相，空间群）。晶格参数研究和X射线能谱分析表明，该相具有较窄的均匀性范围。由霍尔效应测量确定的2 K下的电荷载流子浓度与（/晶胞/晶胞）相关。该相在650 °C范围内具有均匀性。使用所应用的制备条件，对于任一种改性都没有实现理想的Zintl组合物。从X射线吸收光谱和温度和磁场的磁化强度的依赖性，我们发现，在这两个阶段的阳离子的电子配置。据信，Rudermann-Kittel-Kasuya-Yosida相互作用是负责所观察到的铁磁有序。这与本文和另一篇论文[A. Bentien，V.帕切科，S.帕申，于。Grin和F. Steglich，Phys. Rev. B 71，165206（2005）]在该工作中，两相之间的有序化温度的大差异与电荷载流子的有效质量成比例。
The charge carrier concentratioin is an important parameter in the search for intermetallic clathrates adequate for thermoelectric applications. This work reveals the influence of the exact composition ofon the charge carrier concentration. The samples with initial compositionwere processed according to two different heat treatments. Slow cooling of the melt and subsequent annealing produced thephase with clathrate I structure (space group). In contrast, samples quenched from 1040 °C and then annealed showed the clathrate-VIII structure (phase, space group). Lattice parameter investigations and energy dispersive x-ray spectroscopy analysis show that thephase possesses a narrow homogeneity range. The charge carrier concentrationat 2 K, as determined from Hall-effect measurements, correlates with(/unit cell/unit cell). Thephase has a homogeneity range withat 650 °C. The ideal Zintl compositionwas not achieved for either modification using the applied preparation conditions. From x-ray absorption spectroscopy and the temperature and magnetic field dependence of the magnetization we find that the electronic configuration of the cations in both phases is. It is believed that the Rudermann-Kittel-Kasuya-Yosida interaction is responsible for the observed ferromagnetic ordering. This agrees well with the observation made in this and another paper [A. Bentien, V. Pacheco, S. Paschen, Yu. Grin, and F. Steglich, Phys. Rev. B 71, 165206 (2005)] on this work that the large difference in ordering temperature between the two phases scales with the effective masses of the charge carriers.