ISO 25498:2010 微束分析 分析电子显微镜 采用透射电子显微镜的选择区域电子衍射分析

标准编号：ISO 25498:2010

中文名称：微束分析 分析电子显微镜 采用透射电子显微镜的选择区域电子衍射分析

英文名称：Microbeam analysis — Analytical electron microscopy — Selected-area electron diffraction analysis using a transmission electron microscope

发布日期：2010-06

标准范围

ISO 25498:2010规定了使用透射电子显微镜（TEM）进行选区电子衍射（SAED）分析的方法，以分析薄晶体试样的微米和亚微米大小的区域。此类试样可以从各种金属和非金属材料以及细粉末中以薄片的形式获得，也可以使用提取复制品。用这种方法可以分析的样本中所选区域的最小直径取决于显微镜物镜的球差系数，对于现代TEM来说，它接近0.5 mm。当分析样品区域的直径小于0.5mm时，分析程序也可参考ISO 25498:2010，但由于球差的影响，图案中的一些衍射信息可从所选样品定义的区域外部生成-面积孔径。在这种情况下，最好使用微衍射或会聚束电子衍射（如有）。选区电子衍射法的成功取决于对产生的衍射图案进行索引的有效性，而不管试样中的哪个轴平行于入射电子束。因此，这种分析借助于样品倾斜和旋转设备。ISO 25498:2010适用于从晶体样品中获取SAED图案，对图案进行索引并校准衍射常数。

ISO 25498:2010 specifies the method of selected-area electron diffraction (SAED) analysis using a transmission electron microscope (TEM) to analyse micrometer and sub-micrometer sized areas of thin crystalline specimens. Such specimens can be obtained in the form of thin sections from a variety of metallic and non-metallic materials, as well as fine powders, or alternatively by the use of extraction replicas. The minimum diameter of the selected area in a specimen which can be analysed by this method depends on the spherical aberration coefficient of the objective lens of the microscope and approaches 0,5 mm for a modern TEM.When the diameter of an analysed specimen area is smaller than 0,5 mm, the analysis procedure can also be referred to ISO 25498:2010 but, because of the effect of spherical aberration, some of the diffraction information in the pattern can be generated from outside of the area defined by the selected-area aperture. In such cases, the use of microdiffraction or convergent beam electron diffraction, where available, might be preferred.The success of the selected-area electron diffraction method relies on the validity of indexing the diffraction patterns arising, irrespective of which axis in the specimen lies parallel to the incident electron beam. Such analysis is therefore aided by specimen tilt and rotation facilities.ISO 25498:2010 is applicable to acquisition of SAED patterns from crystalline specimens, indexing the patterns and calibration of the diffraction constant.

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