An Improved Mean Atomic Number Background Correction for Quantitative Microanalysis
An Improved Mean Atomic Number Background Correction for Quantitative Microanalysis
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DOI：
10.1017/s1431927696210013
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发表时间：
1996-02
影响因子：
2.8
通讯作者：
J. Donovan;T. Tingle
中科院分区：
文献类型：
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作者：
J. Donovan;T. Tingle
定量电子探针（EPMA）强度测量需要对初级电子束的韧致辐射效应产生的X射线连续谱（或背景）进行精确校正。在波长色散光谱仪上测量的任何特定波长的X射线连续谱主要是被分析材料的平均原子序数的函数。可以通过测量和曲线拟合不含任何分析物或任何干扰元素的纯元素、氧化物和二元化合物标准品中分析峰处的X射线强度来校准连续谱对平均原子序数的依赖性，并使用该校准来计算X射线背景校正。对于未知样品，平均原子序数由ZAF或φ（ρz）矩阵校正计算的元素浓度确定，拟合回归系数迭代用于计算实际背景校正。在较大的平均原子序数范围内，我们发现连续谱强度对平均原子序数的依赖关系可用二阶多项式拟合。在低能X射线线（<1至2 keV）的情况下，通过校正X射线连续谱强度的吸收，这种拟合得到了显着改善。对于主量元素和大多数次量元素的分析，本文提出的改进的平均原子序数背景校正方法是准确的和鲁棒的各种样品。经验平均原子序数背景数据为一个典型的10个元素的硅酸盐和15个元素的硫化物的分析设置，证明该技术的有效性以及一些潜在的局限性。
Quantitative EPMA (electron probe microanalysis) intensity measurements require an accurate correction for the X-ray continuum (or background) created by the Bremsstrahlung effect from the primary electron beam. This X-ray continuum, as measured on a wavelength-dispersive spectrometer at any particular wavelength, is primarily a function of the mean atomic number of the material being analyzed. One can calibrate the dependence of the continuum on mean atomic number by measuring and curve fitting the X-ray intensities at the analytical peak in pure elements, oxides, and binary compound standards that do not contain any of the analyte or any interfering elements and use that calibration to calculate the X-ray background correction. For unknown samples, the mean atomic number is determined from the elemental concentrations calculated by the ZAF or φ(ρz) matrix correction, and the fit regression coefficients are used iteratively to calculate the actual background correction. Over a large range of mean atomic number we find that the dependence of the continuum intensity on mean atomic number is well described by a second-order polynomial fit. In the case of low-energy X-ray lines (<1 to 2 keV), this fit is significantly improved by correcting the X-ray continuum intensities for absorption. For major and most minor element analyses, the improved mean atomic number background correction procedure presented in this paper is accurate and robust for a wide variety of samples. Empirical mean atomic number background data are presented for a typical 10-element silicate and a 15-element sulfide analytical set up that demonstrate the validity of the technique as well as some potential limitations.