低熔点合金助熔剂法二硼化镁单晶生长的研究

项目名称： 低熔点合金助熔剂法二硼化镁单晶生长的研究

项目编号： No.50802081

项目类型： 青年科学基金项目

立项/批准年度： 2009

项目学科： 机械、仪表工业

项目作者： 杜伟

作者单位： 烟台大学

项目金额： 19万元

中文摘要： 于2001年发现MgB2具有超导性质以来，由于其具有潜在而广泛的应用，随即在国际上掀起研究该种材料的热潮。尽管MgB2的化学结构非常简单，但是由于Mg在晶体生长过程中的蒸发导致的非重现性，使得生长高质量的可用于基础研究的高质量单晶非常困难。所以本课题组利用准静态氩气保护系统作为晶体生长装置，采用低熔点合金作为助熔剂的方法进行单晶生长，重点研究MgB2单晶生长的工艺过程。利用现代仪器分析手段（XRD、EDS、SEM、MM、AFM等设备）检测确认样品的结晶习性。通过扫描电子显微镜(SEM)和金相显微镜(MM)对MgB2晶体形貌进行了研究。结果发现(1-11), (101)和(011)晶面的生长速率远远大于(1-10), (100)和 (010)晶面生长速率，即晶体沿a或b轴的生长速率明显很大，而沿c轴的生长速率很小，甚至随着晶体生长并未发生变化。在MgB2单晶中首次观察到{0001}晶面层的解离，根据晶体所展现的微观形貌，解释了MgB2晶体难于长大的原因。

中文关键词： MgB2;单晶生长；超导材料；形貌表征

英文摘要： The discovery of superconductivity at 39 K for MgB2 in 2001 has attracted great scientific interest because of the highest Tc among conventional metals and metal alloy compounds. In spite of the chemical and structural simplicity, growth of high quality single crystals of MgB2 for fundamental studies is very difficult because of the non-reproducibility of Mg evaporation during the growth process. Hexagonal plate magnesium diboride (MgB2) single crystal has been prepared by using Mg flux method. Growth morphology of MgB2 crystals has been investigated by scanning electron microscope (SEM) and metallographic microscope (MM). It is found that the growth velocities of (1-11), (101) and (011) crystal facets are much faster than that of (1-10), (100) and (010) facets and the crystal growth velocity along a or b-axes is obviously increased while the growth velocity along c-axes is very slow or unchanged along with crystal growth. Cleavage along {0001} layer direction is also been firstly found by the observation of hexagonal plate MgB2 single crystal under MM, which is similar to graphite. A possible growth mechanism of MgB2 single crystal was discussed.

英文关键词： MgB2;Crystal growth;Superconducting materials;Morphology characterization