Characterisation

Sample characterization

Single crystal orientation / detection of grain boundaries

Real-Time-Laue-Backscattering-camera system MWL 110, with 30x 30 cm-wide multi-wire proportional chamber with X-ray shutter and a set of 4 interchangeable collimators of different diameter.
joystick-controlled 3-axis goniometer and x-z translation unit for positioning the sample in the X-ray beam. North Star Orientation software for fast indexing of the obtained Laue-reflections. Acuracy of the orientation better than 0.2 ° in normal mode or 0.05° in high resolution mode.

Multiwire Laboratories Ltd. MWL 110

and Lauecamera.com

Crystal orientation to better than 0.2 ° in normal mode and 0.05 ° in high resolution mode. The oriented crystals can be transferred to the wire saw or polishing machines for oriented cuts and polished surfaces.

Laue picture of a CaWO4 crystal. Recorded with a 10 sec exposure time with an accelerating voltage of 14 kV, 20 mA .

Stereographic projection of the solution

X-ray phase analysis / pole figures / x-ray high temperature chamber

· Θ/2Θ diffractograms with computer controlled 2-circle diffractometer The two-circle system is used for powder diffraction. In this system, the samples can be heated in oxidizing, reductive or inert atmosphere up to 1600°C. It is equipped with a Göbel mirror and a position-sensitive detector to save measuring time.

· Pole figures, small angle determination ,Φ- and Χ-Scans with 4 circle diffractometer

· X-ray based determination of phase diagrams in a temperature region up to 1600 °C in any atmosphere.

Scanning Electron Microscopy / EDX

Scanning electron microscopy is a state of the art technique for the analysis and imaging of micro- and nanostructures.
It is equipped with a Tungsten hairpin gun and an Energy Dispersive X-ray (EDX) analysis system. It is mainly used for spatially resolved chemical analyis of bulk and thin film samples.

Right: SEM image of YBa₂Cu₃O_7-_δ crystals with some flux sticking on the surface

Energy Dispersive X-Ray Analysis

Energy Dispersive X-ray (EDX) analysis is a valuable tool for qualitative and quantitative element analysis. This method allows a fast and non-destructive chemical analysis with a spatial resolution in the micrometer regime. It is based on the spectral analysis of the characteristic X-ray radiation emitted from the sample atoms upon irradiation by the focussed electron beam of a SEM. In our system the spectroscopy of the emitted X-ray photons is performed by a Si-Li detector with an energy resolution of about 150 eV at 5 mm working distance.

Operation Principle

The incident beam electrons excite electrons in a lower energy states, prompting their ejection and resulting in the formation of electron holes within the atom’s electronic structure. Electrons from an outer, higher-energy shell then fill the holes, and the excess energy of those electrons is released in the form of X-ray photons. The release of these X-rays creates spectral lines that are highly specific to individual elements. In this way the X-ray emission data can be analyzed to characterize the sample in question. For example, the presence of copper is indicated by two so called K peaks (K_α and K_β) at about 8.0 and 8.9 keV and a L_α peak at 0.85 eV.

Left: Characteristic EDX spectrum obtained from a Ca-doped YBa₂Cu₃O_7-_δ single crystal