Department Microstructure and Residual Stress Analysis

X-ray analysis with high-flux MetalJet sources

Novel high-flux X-ray sources using liquid metal as targets enable X-ray studies in the laboratory that previously only had been possible at synchrotrons. The department runs two laboratories (LIMAX-160, LIMAX-70) equipped with liquid-metal-jet X-ray sources as part of the X-ray Corelab. The focus of experimental methods is on the analysis of phase formations, residual stresses, microstructure, and texture in complex thin film systems and technical components, which are provided for

• in-house POF-relevant research in the field of energy materials,
• external user groups from national and international scientific institutions, and
• industry.

The main scientific objectives are the development and application of advanced measurement and data evaluation techniques, which exploit the specific features of the X-ray spectrum emitted by the liquid-metal-jet source, as well as ex-situ and in-situ studies of energy materials such as photovoltaic absorber films and battery cells. Making use of the strong characteristic Ga Kα (9.2 keV) and In Kα (24.2 keV)  as well as the white bremsstrahlung spectrum of up to 160 keV allows for angle- and energy-dispersive diffraction, fluorescence and imaging experiments.

Left: Pilatus 1M detector, in-situ chamber for real-time analysis of compound semiconductor film growth, Excillum MetalJet X-ray source (D2 with 160 kV) in LIMAX-160. Right: Diffraction rings and integrated intensities (inset) from a Cu(In,Ga)Se₂ film recorded within 10 seconds.

Real-time analysis by two-dimensional X-ray diffraction (2D-XRD)

For the analysis of time-critical reaction processes such as phase formations and microstructure changes, the Ga-K for angle-dispersive 2-dimensional X-ray diffraction (2D-ADXRD). A large area X-ray detector (Pilatus3 S 1M) allows to record diffraction rings within a few seconds, which provides sufficient time resolution for the investigation of various types of solid-state reactions in thin films. (See here for recent results)

Stress, texture and microstructure analysis by energy-dispersive X-ray diffraction

For materials research by energy-dispersive X-ray diffraction (EDXRD), continuous polychromatic X-ray radiation of up to 160 keV generated by bremsstrahlung is utilized. The high energies enable the nondestructive analysis of (residual) stress, crystallographic texture and microstructure in different material regions. In reflection geometry, residual stress depth profiles in the near-surface region up to some hundred micrometres can be recorded. For these experiments, an Eulerian cradle based diffractometer setup with integrated x-y-z translation table can be mounted.

Diffraction and Imaging

The high flux and energy range of the radiation from the metal-jet sources is further suitable for imaging applications. For example, tomographic images of soft matter materials as well as metallic components can be recorded utilizing a set of different detector systems. Thus, the X-ray sources allow for the combination of diffraction and imaging in the laboratory. This hybrid methodology enables insights into material properties that are not accessible with each method on its own.

(a) Excillum MetalJet X-ray source (D2 with 70 kV) equipped with a Huber diffractometer, an Eulerian cradle and a Ge multi-channel analyser in LIMAX-70. (b) Original synchrotron setup for combined imaging-diffraction experiments to be adapted into the lab.

Variable sample environments

The LIMAX laboratories are equipped with various sample environments such as diffractometer systems, heating stations, mechanical load devices and deposition chambers, deployed for experiments in different fields of energy and materials research. To be able to switch between in-house research, external user research, and industry research, the sample environment can be exchanged with the help of a modular mounting system.