Analytical Electron Microscopy and the Problem of Potassium Diffusion
Analytical Electron Microscopy and the Problem of Potassium Diffusion
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分析电子显微镜和钾扩散问题
DOI：
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发表时间：
1988
期刊：
影响因子：
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通讯作者：
D. Peacor
中科院分区：
文献类型：
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作者：
B. A. Pluijm;J. H. Lee;D. Peacor
在分析电子显微镜（AEM）中K的扩散导致该元素的计数率异常低。随着分析面积和试样厚度的减小，计数率不成比例地降低。在AEM过程中，阿杜菌和白云母的扩散曲线不同；对于白云母，已经观察到扩散对晶体取向有很强的依赖性。通过AEM产生可靠化学数据的条件是使用宽扫描面积（>800 × 800 Å）和/或大光束尺寸以减少碱元素扩散的影响，样品厚度大于约1000 Å，恒定的仪器操作条件，以及使用均匀，特征良好的标准样品。在给定的操作条件下，通过确定元件强度比与厚度曲线，得到了最佳厚度范围。标准的和未知的应该有相似的晶体结构，特别是对于强各向异性的矿物，如层状硅酸盐，在电子束方面应该有相似的晶体取向。
Diffusion of K during analytical electron microscopy (AEM) results in anomalously low count rates for this element. As the analysis area and specimen thickness decrease, count rates become disproportionally lower. Adularia and muscovite show different diffusion profiles during AEM; for muscovite a strong dependence of diffusion on crystallographic orientation has been observed. Conditions giving rise to reliable chemical data by AEM are the use of a wide scanning area (>800 × 800 Å) and/or large beam size to reduce the effect of diffusion of alkali elements, a specimen thickness greater than about 1000 Å, constant instrument operating conditions, and the use of a homogeneous, well-characterized standard sample. The optimum thickness range was obtained by determining the element intensity ratio vs. thickness curve for given operating conditions. The standard and unknown should have a similar crystal structure and, especially for strongly anisotropic minerals such as phyllosilicates, a similar crystallographic orientation with respect to the electron beam.