Standard Reference Material (SRM 1990) For Single Crystal Diffractometer Alignment

• Published in: Journal of research of the National Institute of Standards and Technology Vol. 106; no. 6; pp. 1071 - 1094
• Main Authors: Wong-Ng, W, Siegrist, T, DeTitta, G T, Finger, L W, Evans, Jr, H T, Gabe, E J, Enright, G D, Armstrong, J T, Levenson, M, Cook, L P, Hubbard, C R
• Format: Journal Article
• Language: English
• Published: United States National Institute of Standards and Technology 01.11.2001; Superintendent of Documents; National Institute of Standards (NIST); [Gaithersburg, MD] : U.S. Dept. of Commerce, National Institute of Standards and Technology
• Subjects: alignment standard; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; Cr-content; Crystal whiskers; Crystallography; instruments & instrumentation; international round robin; NIST SRM 1990; OTHER INSTRUMENTATION; physics; ruby spheres; single crystal x-ray diffractometers; X-ray diffractometer; United States; ruby spheres; international round robin; Cr-content; NIST SRM 1990; alignment standard; single crystal x-ray diffractometers
• ISSN: 1044-677X; 2165-7254
• DOI: 10.6028/jres.106.058

An international project was successfully completed which involved two major undertakings: (1) a round-robin to demonstrate the viability of the selected standard and (2) the certification of the lattice parameters of the SRM 1990, a Standard Reference Material(®) for single crystal diffractometer alignment. This SRM is a set of ≈3500 units of Cr-doped Al2O3, or ruby spheres [(0.420.011 mole fraction % Cr (expanded uncertainty)]. The round-robin consisted of determination of lattice parameters of a pair of crystals: the ruby sphere as a standard, and a zeolite reference to serve as an unknown. Fifty pairs of crystals were dispatched from Hauptman-Woodward Medical Research Institute to volunteers in x-ray laboratories world-wide. A total of 45 sets of data was received from 32 laboratories. The mean unit cell parameters of the ruby spheres was found to be a=4.7608 ű0.0062 Å, and c=12.9979 ű0.020 Å (95 % intervals of the laboratory means). The source of errors of outlier data was identified. The SRM project involved the certification of lattice parameters using four well-aligned single crystal diffractometers at (Bell Laboratories) Lucent Technologies and at NRC of Canada (39 ruby spheres), the quantification of the Cr content using a combined microprobe and SEM/EDS technique, and the evaluation of the mosaicity of the ruby spheres using a double-crystal spectrometry method. A confirmation of the lattice parameters was also conducted using a Guinier-Hägg camera. Systematic corrections of thermal expansion and refraction corrections were applied. These rubies- are rhombohedral, with space group [Formula: see text]. The certified mean unit cell parameters are a=4.76080±0.00029 Å, and c=12.99568 ű0.00087 Å (expanded uncertainty). These certified lattice parameters fall well within the results of those obtained from the international round-robin study. The Guinier-Hägg transmission measurements on five samples of powdered rubies (a=4.7610 ű0.0013 Å, and c = 12.9954 ű0.0034 Å) agreed well with the values obtained from the single crystal spheres.