Addressing the amorphous content issue in quantitative phase analysis: the certification of NIST standard reference material 676a.
Addressing the amorphous content issue in quantitative phase analysis: the certification of NIST standard reference material 676a.
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DOI：
10.1107/s0108767311014565
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发表时间：
2011-07
期刊：
影响因子：
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通讯作者：
J. Cline;R. V. Von Dreele;Ryan S. Winburn;P. Stephens;J. Filliben
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文献类型：
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作者：
J. Cline;R. V. Von Dreele;Ryan S. Winburn;P. Stephens;J. Filliben
非衍射表面层存在于晶体的任何边界处，并且可以在细分的固体中包括百分之几的质量分数。这导致了定量相分析（QPA）标准品中非晶含量的长期问题。NIST标准参考物质（SRM）676 a是一种α-Al（2）O（3）粉末，经相纯度认证，可用作粉末衍射QPA中的内标。SRM 676a的非晶含量通过比较来自混合物的衍射数据与被设计成改变其比表面积的硅粉末样品来确定。在Si上的非晶表面层的厚度不变的（支持的）假设下，这提供了一种控制SRM 676a与硅的50/50重量混合物的硅组分的结晶/非晶比的方法。利用中子飞行时间和25 keV和67 keV的X射线能量的粉末衍射实验量化的结晶相分数从一系列标本。从Rietveld分析，其中包括在硅中的消光效应的模型，这些数据的结果外推到硅粉末的零无定形含量的限制。SRM 676 a的经认证相纯度为99.02% ± 1.11%（95%置信区间）。这种新的认证方法允许通过加标SRM 676a来定量任何感兴趣样品的无定形含量。
A non-diffracting surface layer exists at any boundary of a crystal and can comprise a mass fraction of several percent in a finely divided solid. This has led to the long-standing issue of amorphous content in standards for quantitative phase analysis (QPA). NIST standard reference material (SRM) 676a is a corundum (α-Al(2)O(3)) powder, certified with respect to phase purity for use as an internal standard in powder diffraction QPA. The amorphous content of SRM 676a is determined by comparing diffraction data from mixtures with samples of silicon powders that were engineered to vary their specific surface area. Under the (supported) assumption that the thickness of an amorphous surface layer on Si was invariant, this provided a method to control the crystalline/amorphous ratio of the silicon components of 50/50 weight mixtures of SRM 676a with silicon. Powder diffraction experiments utilizing neutron time-of-flight and 25 keV and 67 keV X-ray energies quantified the crystalline phase fractions from a series of specimens. Results from Rietveld analyses, which included a model for extinction effects in the silicon, of these data were extrapolated to the limit of zero amorphous content of the Si powder. The certified phase purity of SRM 676a is 99.02% ± 1.11% (95% confidence interval). This novel certification method permits quantification of amorphous content for any sample of interest, by spiking with SRM 676a.