Non-wetting crystal growth of Mg2Si by vertical Bridgman method and thermoelectric characteristics
Non-wetting crystal growth of Mg2Si by vertical Bridgman method and thermoelectric characteristics
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DOI：
10.1016/j.jcrysgro.2006.10.270
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发表时间：
2007-06-01
影响因子：
1.8
通讯作者：
Takanashi, Yoshifumi
中科院分区：
文献类型：
--
作者：
Akasaka, Masayasu;Iida, Tsutomu;Takanashi, Yoshifumi
采用垂直布里奇曼法在非润湿生长环境中生长了镁硅化物（Mg 2Si）晶体，通过在坩埚壁上涂上防粘涂层来实现。高反应性熔融镁（Mg）、硅（Si）和Mg 2Si的最小化粘附允许容易地从坩埚移除生长的锭，并且生长的锭的外部形状遵循坩埚的内壁形状。生长的晶体是单相的多晶Mg 2Si-X射线分析，如Lane背反射和Lang透射形貌图显示所获得的晶粒本质上是单晶。采用生长放电质谱法（GDMS）研究了工艺过程中产生的污染物。生长的晶体表现出n型导电性，这可能是由于所使用的Mg源材料中的残留杂质和生长过程中无意的杂质掺入。由于Mg 2Si是热-电能量转换的候选材料，因此测量了热电性能，如塞贝克系数S、电导率σ和热导率κ，作为温度的函数，直至873 K。压铸工艺诱导的热电性能的特点进行了讨论。在656 K时，最大无量纲优值估计为0.17。(C)2007 Elsevier B. V.保留所有权利。
Magnesium siliside (Mg2Si) crystals have been grown using the vertical Bridgman method in a non-wetting growth environment, achieved by the use of an anti-adhesion coating on the crucible wall. The minimized adhesion of highly reactive molten magnesium (Mg), silicon (Si) and Mg2Si permitted easy removal of the grown ingot from the crucible, and the external shape of the grown ingot followed the shape of inner wall of the crucible. The grown crystals were a single phase of polycrystalline Mg2Si-X-ray analysis, such as Lane back-reflection and Lang transmission topographs revealed that grains obtained were single crystal in nature. Process induced contaminants were investigated by using grow discharge mass spectrometry (GDMS). The grown crystals exhibited n-type conductivity, which could result from the residual impurities in the Mg source material used and unintentional impurity incorporation during growth. Since Mg2Si is a material candidate for thermal-to-electric energy-conversion, the thermoelectric properties such as Seebeck coefficient, S, electrical conductivity, sigma, and thermal conductivity, kappa, were measured as a function of temperature up to 873 K. Die-casting process induced characteristics of such thermoelectric properties are discussed. The maximum dimensionless figure-of-merit was estimated to be 0.17 at 656K. (C) 2007 Elsevier B.V. All rights reserved.