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Laboratory of X-ray Diffractometry and Spectrometry

Laboratory of X-ray diffractometry and spectrometry is part of the Central Laboratories at the University of Chemical Technology in Prague. Its main mission is the determination of phase composition using X-ray diffraction analysis(XRD) involving the measurement and evaluation of diffraction patterns and elemental composition by X-ray fluorescence analysis (XRF) of samples supplied from university departments but also from outside the university. In addition to the basic service, specialized or complex experiments, including evaluation can be performed.

X-ray powder diffraction analysis (XRPD, mineralogical analysis, phase analysis) could be used to measure solid samples in the form of powders or flat compacts to determine amorphous or crystalline state of samples. The determination of crystalline phases is performed on the base of comparison  measured d, I values with d,I values in databases PDF-4+(Powder diffraction file, inorganic measured and calculated data) or PDF-4/Organics (organic calculated data). Database PDF-4+ includes cards (reference 04-) with x,y,z coordinates of atoms, which could be used for quantitative Rietveld`s analysis.

XRD analysis is mainly used to characterise solid samples, inorganic and organic. Laboratory deals with all chemical problems having relation to solid phase, solid state reactions and heterogeneous systems. It can provide information about progress of solid state reaction, about qualitative and quantitative phase composition of solids, crystalline polymorphism, crystallite size (1-500nm), degree of crystallinity, structural perfection, texture. Special area is molecular and crystal structure of organic or inorganic compounds from single crystals, high-temperature  measurement of powders in the range 20-1400°C.

XRD became an indispensable method for studies of corrosion processes, catalytic reactions, synthesis of ceramic materials and pharmaceutic substances(API), research of semiconductors. XRD is not a trace analysis,  0.1 hm.%. is the Limit of Detection(LOD). Recommended quantity of sample for XRD is in section Service. XRD measurement is non-destructive and sample can be used for another analysis.

MicroXRD deals with spot analysis in range 0.1-2 mm. The main advantage is possibility to analyse no-plane compacts in different shapes (e.g. pipes, wires).

X-Ray fluorescent analysis is used to determine elements in range Be-U in powders or compact samples. It is possible to measure liquids as well with restriction to range F-U and worse detection limits for F-Si. Liquids are measured in cups, bottom of the cup is foil, usually 6 micrometer mylar or 4 micrometer polypropylene. Measured liquid must not react with foil, preferably having pH in range 5-7(F-Mg are measured with WD spectrometers). Thera are almost no restriction on pH and reactivity of liquid when ED spectrometer is used, but only Al-U elements can be measured. XRF is suitable for determination of more elements simultaneously (standard F-U), limit of detection generally  improves with growing atomic (proton) number, advantage is low overlap among elements, light elements Be-Si should be measured on samples with  smooth surface.  This is really necessary for Be-O. Recommended quantity of sample for XRD is in section Service. The measurement is mostly non-destructive (warning-glass may darkened). The element composition of glass, cements, ashes, clays, alloys is the main application.

X-ray single crystals diffraction is used for determination of molecular and crystal structure of organic or inorganic moleculs(up to 100 nonH atoms in asymmetric part of cell). Single crystal with size in range 100-1000microns is necessary. Growing of single crystals from solutions can be performed in laboratory, at least 50mg of sample and knowledge about solubility in different solvents is necessary.

Updated: 19.7.2018 10:37, Author: Jan Prchal

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