General

X-ray diffraction analysis is a non-destructive method for the structural analysis of crystals. The most important field of application is the identification of the crystalline components, i.e. the different crystalline phases contained in the mixture are identified. Mainly we analyse powdery samples, but also piece goods can be analysed. WZR ceramic solutions GmbH cooperates with an external partner in this field. This partner carries out the measurement while the preparation and evaluation take place in-house. Thus an optimal weighting from most modern analysis methods, evaluation of specialists and attention of the costs is given.

Röntgendiffraktometer
Figure 1: X-ray diffractometer

For the investigations, a characteristic monochromatic X-ray radiation is generated, which is directed onto the sample to be analyzed and, after interaction with the sample, the diffracted radiation is detected (Fig. 2).

Schematische Darstellung der RBA
Figure 2: schematic representation of the XRD

The investigation method is based on the diffraction of the X-rays at the lattice planes of the crystals. The active principle is described by the BRAGG´sche equation (Figure 3).

Wirkungsweise der RBA
Figure 3: Mode of action of the XRD

Samples as piece goods with flat surface as well as powder can be analyzed.
The investigation of crystalline powders is also referred to as powder diffraction, which produces powder patterns (Fig. 4). The powder diffractogram contains the recorded intensities of the X-rays diffracted at the crystal lattice planes as a function of the diffraction angle in a certain range of 2Theta. The recorded peaks are compared with databases and thus identified, i.e. qualified. Depending on the intensity of the recorded diffraction data, a quantification of the components can be performed with a complete qualitative analysis (Rietveld analysis). The intensity itself depends on numerous complex factors, e.g. wavelength of the used X-rays, area frequency, polarization, Lorentz and structure factor. Depending on the task, there are different methods for quantifying the batch analysis.

Services and support

WZR ceramic solutions GmbH (CerCheck)® offers the following services:

  • Sample preparation and sample preparation
  • Qualification of the crystalline phase inventory of single-phase and multi-phase mixtures
  • Quantification of the crystalline phase inventory of multiphase mixtures
  • Quantification of amorphous phase content by internal standard

In principle, it should be noted that phase contents of < 5 Ma.-% cannot be verified statistically with X-ray diffraction analysis. The relative error in the quantitative evaluation depends on the phase content and decreases with increasing phase content.

Sample geometry:

  • a flat surface is also required for piece goods
    • Maximum specimen diameter 39 mm (appropriate preparations can be carried out in-house)
  • For routine determinations of samples already ready for analysis, we require homogeneous powders in the following grain sizes and minimum sample quantities:
    • for a qualitative analysis: dmax < 80 µm, min. 1 g
    • for quantitative analysis: dmax < 63 µm, min. 2 g (double determination).

Narrowing the chemistry of the sample can facilitate and speed up the analysis. Furthermore, information on the problem and the previous sample preparation is always desirable in order to ensure the most effective analysis possible.

In the case of special questions, further preparation of the analysis material and a larger sample quantity may be necessary. We would be pleased to advise you personally. Talk to us!

Examples of methods

With the X-ray diffraction analysis can be examined:

  • natural and technical raw materials and products
  • Raw materials for ceramics and ceramic products, such as medical technology products, refractory materials, etc.
  • cement raw materials
  • Metals, e.g. austenite, martensite, detection of crystalline corrosion products

X-ray diffraction analysis can be used to determine and record:

  • stoichiometric composition of phases
  • crystalline impurities
  • Mineral conversions such as quartz to cristobalite with the associated increase in volume
  • New mineral formations, e.g. due to temperature effects in technical processes, e.g. formation of feldspars, damage in large technical plants
  • Dependence of the degree of crystallization on the course of the process

application examples

Picture 4: Composition of a raw sample bentonite, detecting the phase content
Picture 5: Detection of the conversion of quartz into cristobalite in a SiC sample after application of the test material