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Certification of Standard Reference Material® 640g: Line Position and Line Shape Standard for Powder Diffraction (Silicon Powder)



James Cline, Marcus Mendenhall, David R. Black, Albert Henins, Jack Prothero


NIST certifies a suite of Standard Reference Materials (SRMs) to be used to evaluate specific aspects of the instrument performance and measurements via the powder diffraction technique. This includes machines that utilize X-rays, both synchrotron and laboratory-based sources, and neutron powder diffractometers. This report describes the preparation and certification of SRM 640g, the eighth generation of this powder diffraction SRM, which is designed to be used primarily for calibrating powder diffractometers with respect to line position. A unit consists of approximately 7.5 g of silicon powder prepared from intrinsic, float-zone boules. The boules were crushed and ultimately jet milled to a narrow particle size distribution centered on 4 micrometers, and with none smaller than 2.5 micrometers. The powder was then annealed at a temperature and time sufficient to eliminate crystallographic defects. Given that the lower particle size limit and the annealing process precluded sample induced line profile broadening, the SRM can also be used for the determination of the instrument profile function on equipment utilizing laboratory X-ray sources. It can also be used for evaluation of high-resolution equipment; however, advanced data analysis strategies must be employed. The SRM is certified with respect to the lattice parameter, with the SI traceability of the measurements being through the Cu Kα emission spectrum of the X-ray source that was used. A NIST-built diffractometer, incorporating many advanced design features, was used to provide data for the certification of the lattice parameter. Both statistical and systematic uncertainties have been assigned to yield a certified value for the lattice parameter at 22.5 °C of a = 0.5431144 nm with an expanded uncertainty (k = 2) interval of ± 0.000008 nm. Prior to comminution, the lattice parameter of single-crystal silicon specimens cut from the boules was measured using the NIST lattice comparator. A value of 0.543102055 nm ± 0.000000027 nm was obtained.
Special Publication (NIST SP) - 260-245
Report Number


certification, diffractometer, lattice parameter, powder diffraction, Standard Reference Material (SRM), Système International (SI), silicon.


Cline, J. , Mendenhall, M. , Black, D. , Henins, A. and Prothero, J. (2024), Certification of Standard Reference Material® 640g: Line Position and Line Shape Standard for Powder Diffraction (Silicon Powder), Special Publication (NIST SP), National Institute of Standards and Technology, Gaithersburg, MD, [online],, (Accessed April 17, 2024)
Created February 27, 2024