What is the unit of the X-ray beam

X-ray diffractometry (XRD)

There are three diffractometers available on the fem:

Siemens D5000
X-rays: Cr Ka, Cu Ka | Primary optics: polycapillary | Detector: scintillation counter | Special feature: Euler cradle
Bruker D8 Discover in GADDS configuration
X-ray radiation: Cu Ka | Primary optics: Göbel mirror, round screen | Detector: 2D area detector Vantec-500 | Special features: spatial resolution, focusing with laser video unit, high temperature diffractometry
Bruker D8 Discover Da Vinci
X-rays: Cr Ka, Mo Ka | Primary optics: Göbel mirror, divergence diaphragm (fixed, variable) | Detector: 1D strip detector Lynxeye XE-T | Special feature: energy discrimination of the detector, Bragg-Brentano geometry, GIXRD (measurements under grazing incidence), transmission measurements, XRR


X-ray diffractometry for the investigation of metals

X-ray diffraction refers to the diffraction of an X-ray beam on crystalline samples with an ordered periodic structure. With the three diffractometers on the fem, everyone can crystalline materials such as metals, ceramics, thin layers and nanoparticles examined and various information about samples obtained:

  • Qualitative phase inventory (precipitations in metal alloys, solid solution hardening, etc.)
  • Quantitative phase composition (e.g. residual austenite content in steels)
  • Microstructure (crystallite size, micro-stresses)
  • Crystallographic texture (e.g. comparison of cold-rolled sheets)
  • Residual stresses (e.g. surface hardened steel)
  • Amorphous part (e.g. metallic glasses)
  • In-situ investigations at high temperatures in various atmospheres up to 900 ° C (e.g. phase changes)

Examples of possible investigations:
Depth profile of residual stresses in surface-hardened steel (left), texture measurement on cold-rolled copper sheet (right), in-situ investigation of phase changes in the nickel-tin system (below)


X-ray diffractometry in the field of surface technology

X-ray diffraction refers to the diffraction of an X-ray beam on crystalline samples with an ordered periodic structure. With the three diffractometers on the fem, everyone can crystalline materials such as metals, ceramics, thin layers and nanoparticles and various information about samples can be obtained:

  • Qualitative phase inventory (e.g. anode deposits in galvanic baths, dispersion deposits, surfaces in various modifications such as cubic and hexagonal boron nitride or molybdenum nitride)
  • Quantitative phase composition with Rietveld analysis
  • Microstructure (e.g. crystallite size of catalyst coatings)
  • Crystallographic texture and correlation with properties
  • Residual stresses (e.g. residual stresses in thin layers depending on process conditions)
  • Amorphous part (e.g. in the nickel-phosphorus system)
  • In-situ investigations at high temperatures in various atmospheres up to 900 ° C (e.g. phase changes in galvanic layer systems)

For surface technology, the Information depth an important role. With X-ray diffractometry, it can be adapted to the respective question by choosing the experimental conditions (calculated information depth of the X-ray radiation in a galvanized sample):

  • Bragg-Brentano geometry with copper Ka radiation: information depth 2.3 µm
  • Bragg-Brentano geometry with molybdenum Ka radiation: information depth 18.5 µm
  • Grazing incidence below 1 ° with copper Ka radiation: information depth 300 nm

Molybdenum radiation can also be used to examine thicker layer systems and samples can also be examined in a surface-sensitive manner using X-ray diffraction under grazing incidence (Gracing Incidence X-Ray Diffraction, GIXRD).

Beam path of the X-rays from the X-ray tube via the sample (S) to the detector (D) in XRD with grazing incidence for surface-sensitive examinations