International
Tables for
Crystallography
Volume H
Powder diffraction
Edited by C. J. Gilmore, J. A. Kaduk and H. Schenk

International Tables for Crystallography (2018). Vol. H, ch. 3.10, pp. 377-379

Section 3.10.5. Crystalline single phases

L. León-Reina,a A. Cuesta,b M. García-Maté,c,d G. Álvarez-Pinazo,c,d I. Santacruz,c O. Vallcorba,b A. G. De la Torrec and M. A. G. Arandab,c*

aServicios Centrales de Apoyo a la Investigación, Universidad de Málaga, 29071 Málaga, Spain,bALBA Synchrotron, Carrer de la Llum 2–26, Cerdanyola, 08290 Barcelona, Spain,cDepartamento de Química Inorgánica, Cristalografía y Mineralogía, Universidad de Málaga, 29071 Málaga, Spain, and dX-Ray Data Services S.L., Edificio de institutos universitarios, c/ Severo Ochoa 4, Parque tecnológico de Andalucía, 29590 Málaga, Spain
Correspondence e-mail:  g_aranda@uma.es

3.10.5. Crystalline single phases

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All of the single phases were selected according to several parameters, such as relevance to selected applications, purity, particle size of the powder and preferred orientation. In order to check the suitability of the crystal structures used, all of the phases were first studied using powder diffraction with Mo Kα1 radiation. These preliminary studies were of special interest for organic phases, as the CIF files obtained from the Cambridge Structural Database (CSD) did not contain the atomic displacement parameters (ADPs). For lactose and fructose, the ADPs were obtained from the original publications and were introduced manually into the GSAS control file. For glucose and xylose, the ADP values were not reported in the original publications. Hence, they were obtained from the fits to the Mo Kα1 patterns for the single phases. Three groups of isotropic ADPs were refined: those for O, C and H atoms. The final ADP values are given in León-Reina et al. (2016[link]) as well as the RF values before and after optimization, showing the improvements in the fits. For RQPA of all of the mixtures the ADPs were kept fixed.

Preferred orientation was modelled by the March–Dollase algorithm along the [001] axis for both glucose and lactose. Since microparticle sizes and distributions for different phases may result in some sample-related effects, such as preferred orientation, microabsorption and `rock-in-the-dust/graininess' effects, all powders were characterized by scanning electron microscopy (SEM). Fig. 3.10.2[link] shows SEM micrographs for all of the phases. All inorganic samples were single phases except for gypsum and insoluble anhydrite. The impurity-phase contents for these two samples were reported in León-Reina et al. (2016[link]).

Both organic and inorganic phases were also measured using Cu Kα1 radiation in reflection mode. As expected, a transparency effect was observed in the Cu Kα1 patterns for organic samples (Buhrke et al., 1998[link]).

References

Buhrke, V. E., Jenkins, R. & Smith, D. K. (1998). A Practical Guide for the Preparation of Specimens for X-ray Fluorescence and X-ray Diffraction Analysis. New York: Wiley.Google Scholar
León-Reina, L., García-Maté, M., Álvarez-Pinazo, G., Santacruz, I., Vallcorba, O., De la Torre, A. G. & Aranda, M. A. G. (2016). Accuracy in Rietveld quantitative phase analysis: a comparative study of strictly monochromatic Mo and Cu radiations. J. Appl. Cryst. 49, 722–735.Google Scholar








































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