Addressing the amorphous content issue in quantitative phase analysis : the certification of NIST SRM 676a.
- X-Ray Science Division
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 ({alpha}-Al{sub 2}O{sub 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.
- Research Organization:
- Argonne National Laboratory (ANL)
- Sponsoring Organization:
- SC; Swedish Research Council; Outokumpu Research Foundation; Korean Government
- DOE Contract Number:
- AC02-06CH11357
- OSTI ID:
- 1032001
- Report Number(s):
- ANL/XSD/JA-65714
- Journal Information:
- Acta Crystallographica Section A: Foundations of Crystallography, Journal Name: Acta Crystallographica Section A: Foundations of Crystallography Journal Issue: 4 Vol. 67A; ISSN 0108-7673
- Country of Publication:
- United States
- Language:
- ENGLISH
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