Commission on Powder Diffraction

Hillier, S. (2002) Spray drying for X-ray powder diffraction specimen preparation. IUCR Commission on Powder Diffraction, Newsletter 27, 7-9. 

Commission on Powder Diffraction lUCr Newsletter, No. 28, Deeember... 

The successful testing of DDM method for structure refinement purposes allows us to predict its applicability in other fields of powder diffraction, such as the analysis of microstructure and quantitative phase analysis (QPA). Trial runs of DDM for the XRD data supplied by the International Union of Crystallography Commission on Powder Diffraction for the Size-Strain and QPA round-robins gave encouraging results. Respective examples are included in the DDM program package. In particular, the biases in the phase contents determined by DDM refinement for the QPA round-robin samples from the weighted amounts were less than 1 wt.%. 

This chapter focuses on the application of quantitative phase analysis (QPA) techniques for the extraction of phase abundance from diffraction data. Rather than repeat the extensive coverage of the QPA methodology covered in other texts, the focus will be on the basis and application of the most commonly used techniques. These were identified from participant responses to the recent round robin on QPA sponsored by the International Union of Crystallography (lUCr) Commission on Powder Diffraction (CPD). By far the greatest number of participants in that study used whole pattern (Rietveld based) methods but there are still several users of traditional single peak based methods and there are still many applications for which these methods suffice. Issues in the measurement of precision and accuracy will also be discussed. 

I. C. Madsen, N. V. Y. Scarlett, F. M. D. Cranswick and T. Fwin, Outcomes of the International Union of Crystallography Commission on powder diffraction round robin on quantitative phase analysis Samples la to Ih, J. Appl. Crystallogr., 2001, 34, 409-426. 

The three-letter framework-type codes, recognized by the IUPAC Commission on Zeolite Nomenclature, have been used to organize the entries in this publication. The powder diffraction data and simulated patterns for the reference structures are listed alphabetically according to the respective framework type code. An index of material names, and associated three-letter codes, is included in the companion volume, the Atlas of Zeolite Framework Types (Baerlocher, McCusker and Olson (2007)). 

Powder diffraction techniques are used on a routine basis by many zeolite scientists. Probably the most common application is the use of a powder diffraction pattern as a fingerprint in the identification of synthesis products. Ideally, a laboratory should have a set of standard zeolite patterns measured on the in house instrument for direct comparison. For laboratories without such a set of patterns or for those whose set is incomplete, the Synthesis Commission of the IZA has published experimental patterns for some zeolites in the book entitled Verified Syntheses ofZeolitic Materials [35] (also available on the internet at http //www.iza-synthesis.org/), and the Structure Commission has published a book entitled Collection of Simulated XRD Powder Patterns for Zeolites [36], which contains at least one representative powder diffraction pattern for each known framework type. An up-to-date internet version of the latter that includes data for newly approved framework types, is maintained at http //www.iza-structure.org/databases/. 

W. M. Meier and D. H. Olson, Atlas of Zeolite Structure Types, Structure Commission of the International Zeolite Association, 1978 It has recently been demonstrated that the use of synchrotron x-ray sources permits single crystal studies to be carried out on much smaller samples. P. Eisenberger, J. B. Newsam, M. E. Leonowicz, and D. E. W. Vaughan, Nature 309 45 (1984) The use of Rietveld refinement techniques allows better. structural information to be obtained from powder diffraction data. W. I. F. David, W. T. A. Harrison, and M. W. Johnson, in High Resolution Powder Diffraction, Materials Science Forum, vol. 9 (C. R. A. 

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