Year: 2002
Type: conference-abstract
Abstract: An empirical evaluation of data obtained using parallel beam geometry powder diffraction from laboratory sources is presented based on signal to noise ratios, count times, and Rietveld refinement of data from NIST standards.Two distinct geometries were used, Debye-Scherrer and reflection, as well as point detectors and a linear position-sensitive detector.The diffraction geometries used include: 1. Parabolic multilayer optic coupled into an asymmetric Si (220) channel-cut two-bounce crystal with a similar crystal on the receiving side.2. Parabolic multilayer optic on the incident beam side and soller collimator on the receiving side.3. Parabolic multilayer optic on the incident beam side and flat multilayer optic on the receiving side.4. Parabolic multilayer optic on the incident side with a linear position-sensitive detector on the receiving side.With respect to conventional Bragg-Brentano geometry, the parallel beam systems provide accurate lattice parameters and highly reliable peak locations.The peak widths as a function of angle can be modeled using Cagliotti parameters and show no significant problems.However, it is apparent from Rietveld refinement that the systems that incorporate multilayer optics without crystal optics provide data that is slightly different than that obtained using parafocusing systems.In particular, the peak tails and location of the α two components are not correctly modeled when using traditional approaches.
Authors: M. Allaire, L. E. Berman, E. D. Johnson, D. P. Siddons, Z. Yin, V. Stojanoff
Institution: Alfred University
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: bronze
Funder: U.S. Department of Energy
Awards: G338944111, G5292656900, G969889393
OpenAlex ID: W2012970302