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X-ray Diffraction

The X-ray Diffraction Laboratory offers an array of powder X-ray diffraction methods. It provides services mainly to internal staff members, but smaller orders can also be arranged for individuals as well as the cooperation with science and education departments.

Range of Services

  • Qualitative phase analysis of geological and synthetic materials
  • Quantitative phase analysis of geological and synthetic materials (Rietveld method)
  • Quantitative phase analysis including estimates of the amount of amorphous component in samples
  • Phase analysis of compact samples (polished sections, uncovered thin sections, mineral fragments)
  • Clay fraction separation
  • Separation and phase analysis of clay minerals

Method Description

Powder X-ray Diffraction (PXRD) is a standard method for analyzing solids. It provides information on the phase (i.e. mineralogical) composition of samples (phase analysis) and the crystal structure of substances (structural analysis). The method is able to identify around 300,000 crystalline phases by comparing the recorded diffraction pattern with the datasets in the Powder Diffraction File (PDF-2 2018) database. The detection limit of the method ranges from about 0.2 to 0.5 wt.% depending on the nature (crystallinity) of the phase being searched for. A (semi-)quantitative phase analysis of mixtures can be performed. The total amount of the amorphous phase in a sample (e.g., glass in fly ash, pyroclastic rocks) can also be estimated. The PXRD method can also be used to accurately determine unit-cell parameters, crystallite size (or the size of coherently diffracting domains), macroscopic stresses and microscopic strains.

Equipment

  • Bruker D8 Advance powder diffractometer (CuKa and CoKa X-ray lamps, LynxEye XE detector, automatic divergence aperture, focusing Goebel mirror, XYZ sliding table for non-standard larger samples (polished sections, thin sections, solid blocks). The instrument provides the possibility of measuring samples in basic Bragg-Brentano geometry, Debye-Scherrer geometry with a focusing Goebel mirror and in transmission mode (sample placed on a flat foil). The diffractometer is equipped with accessories for microdiffraction (collimators, a camera above the sample)
  • Centrifuge for separation of clay minerals
  • LAC laboratory furnace, LE type
  • McCrone mill
  • “In-house constructed“ temperature chamber (max. air temperature of 150 °C)

Personnel

RNDr. František Laufek, Ph.D. (Head of Laboratory, crystallography, XRD phase analysis)

Mgr. Magdaléna Koubová, Ph.D. (clay mineralogy, XRD phase analysis)

RNDr. Michal Čurda (technician)

Sample Requirements

  • The optimum amount of a standard powder sample for quantitative phase analysis ranges between 3–5 g. We are able to homogenize and pulverize smaller samples in-house (agate and corundum bowls, steel mortar). Larger rock fragments/samples (e.g., drill cores) must be homogenized in another laboratory
  • Compact samples can also be measured – uncovered thin sections and polished sections, or other solid samples. The samples must have a flat surface. Microdiffraction can be used to analyze small flat areas of samples (e.g., grains in a polished section), whereby the minimum size of the analyzed area is approximately 200 µm
  • The laboratory performs separation and subsequent phase analysis of the clay fraction. Additional sample “treatments“ (K-saturation, tempering at 110 °C, 300 °C, 550 °C, etc.) can also be carried out upon agreement. The laboratory identifies mixed-layer clay minerals by modelling measurements with the aid of suitable programmes. The minimum sample quantity for clay fraction separation ranges between 10–20 g (depending on the clay fraction content)
X-ray diffractometer
Detail view of the goniometer of the Bruker D8 Advance X-ray powder diffractometer with holders for various types of samples | Author: František Laufek
Práškový rentgenový difraktometr Bruker D8 Advance
Bruker D8 Advance powder X-ray diffractometer | Author: František Laufek
Separace jílové frakce
Clay fraction separation | Author: Magdaléna Koubová

Price list

410
Data collection (Bragg-Brentano)
500 CZK
414
Data collection (Debye-Scherrer)
750 CZK
420
Data evaluation, qualitative phase analysis

single phase

data interpretation only, data collection the evaluation (code 410) is not included
300 CZK
421
Data evaluation, oriented clay specimen

data interpretation only, data collection (code 410) and separation of clay fraction (code 460) are not included
600 CZK
422
Data evaluation, qualitative phase analysis

phase mixture

data interprretation only, data collection (code 410) is not included

 
700 CZK
430
Data evaluation, (semi)quantitative phase analysis

Rietveldova method

data interpretation only, data collection (code 410) is not included
1 000 CZK
432
Quantitative analysis calculated from chemical and qualitative phase analysis

data interpretation only, data collection (code 410) is not included
1 400 CZK
433
Data evaluation, (semi)kvantitative phase analysis

Rietveldova metoda, including estimate of amorphous phase

data interpretation only, data collection (code 410) is not included
1 100 CZK
460
Separation of clay fraction and preparation of oriented specimen
650 CZK
461
XRD mineralogical analysis of soil

XRD analysis of bulk sample and separated clay fraction, Ca, K-saturation of clay fraction, sample temperature at 110 °C, 330 °C and 550 °C and basic evaluation are included

only after previous consultation
8 000 CZK
470
Special work

structure analysis, microstructure analysis, specific sample preparation procedures, semi-quantitative phase analysis of bentonites, micro-diffraction, consultation
600 CZK / 1 hour
480
Fine milling in the McCrone Mill

only in combination with the code 410 analysis
100 CZK

Frequently Asked Questions

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The optimum quantity for qualitative (!) phase analysis of whole-rock samples is about 0.1–0.5 g. It is possible to analyse smaller quantities (lower limit is approx. 5 mg), but it is always the case that the quality of the record is proportional to the quantity of the sample. The price of qualitative phase analysis is 300 CZK for the acquisition of the XRD record and 700 CZK for its evaluation. In total 1000 CZK for 1 sample.

For optimal results of quantitative phase analysis, approximately 3 g of sample is required. Quantitative phase analysis is possible in principle even with a smaller amount of sample, but the result may be burdened with a larger error. The cost of semi-quantitative phase analysis is 300 CZK for the acquisition of the XRD record and 1000 CZK for its evaluation. In total, 1 300 CZK for 1 sample.

Firstly, it is necessary to consider what type of analysis/information the contracting authority requires. If the output is qualitative information, the sample contains mainly kaolinite, less chlorite and a minor amount of smectite, then about 50–500 mg of sample is fully sufficient. Smaller quantities may be analysed, but it is always the case that the quality of the XRD record is proportional to the quantity of the sample. The price is 300 CZK for the X-ray recording and 1 000 CZK for the evaluation (semi-quantitative evaluation).
If the desired output is a detailed phase analysis of clay minerals including the identification of so-called mixed-layered clay minerals, approximately 10–20 g of sample is required depending on the clay fraction content (the sample should be delivered unground as a rule!). The minimum scope of work includes separation and subsequent analysis of the clay fraction.

The price for 1 sample includes:
separation of the clay fraction.........650 CZK
acquisition of XRD records.....2x300 CZK (at least two records are needed)
basic evaluation.........600 CZK
therefore a total of 1 850 CZK

For soil analyses and other special analyses of the clay fraction, however, a number of additional "treatments" are required and the price for 1 sample is always agreed individually.

Normal samples can be supplied as is (see above for optimum quantities). We grind them to the optimum fineness using our own efforts (agate bowls, McCrone mill). Samples for the separation of the clay fraction must be delivered unground as a matter of principle. Larger fragments of coarse-grained rocks, including drill cores, are homogenised in cooperation with the Homogenisation Laboratory. For the analysis of each sample, the acquisition of XRD data (e.g. code 410) and its evaluation (e.g. code 430) is required. Localisation is not necessary. Basic petrographic characterization (or description of the sample – slag, mortar, mica concentrate, etc.) is very useful for evaluating XRD records.

No. The laboratory has a technique called micro-diffraction, which allows the analysis of limited small areas/fragments. The minimum size of the analysed area is approximately 200 μm. For smaller grains, the recording will interfere with the surrounding minerals and will be of very low intensity.

Depends on the viewpoint. This is powder diffraction, where ideally the sample is ground to a powder of 5–10 μm. If you consider pulverizing the sample to be "destructive", then the analysis is destructive. However, 99.9% of the sample analysed is available for further analysis after XRD analysis. From this perspective, XRD analysis is non-destructive.

Yes. The minimum size of the fragment to be separated depends on many other parameters (single crystal x polycrystal, crystallinity of the substance, etc.). The laboratory has a set of separation tools (tweezers, needles) and it is possible to perform the separation of the grain in place.

Yes. We use the standard addition method (ZnO). This method can be applied e.g. in semi-quantitative phase analysis of fly ash and pyroclastic rocks.

Uncovered thin sesctions can be measured.

The detection limits depend on the nature of the phase being analysed, especially how well the mineral diffracts in a particular sample (this is affected in particular by the size of the coherently diffracting domains, the presence of defects, the content of heavy atoms in the structure). In general, the detection limits for common rock-forming minerals are about 0.2–0.5 wt. %. Quartz, galena and other well-diffracted phases have an even lower detection limit. In contrast, materials with a high degree of structural disorder (Fe-oxo-hydroxides, smectites) have significantly higher detection limits.

To a reduced extent, yes. Soils are a very complicated system from a mineralogical point of view and their mineralogical analysis is not a simple task. Analyses are also time consuming and are carried out on selected samples in agreement with the client. It is necessary to count on an approximate price of about 4 500 CZK per sample (depending on the agreement and the number of "treatments" performed).

No. I recommend contacting the CGS Central Laboratory at Barrandov.