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Gerhard Materlik

Publications and source records attributed to Gerhard Materlik.

4 recordsLinked to original sources
PubMed2004

An X-ray BBB Michelson interferometer.

A new X-ray Michelson interferometer based on the BBB interferometer of Bonse and Hart and designed for X-rays of wavelength approximately 1 A was described in a previous paper. Here, a further test carried out at the SPring-8 1 km beamline BL29XUL is reported. One of the BBB's mirrors was displaced by a piezo to introduce the required path-length difference. The resulting variation of intensity with piezo voltage as measured by an avalanche photodiode could be ascribed to the phase variation resulting from the path-length change, with a small additional contribution from the change of the position of the lattice planes of the front mirror relative to the rest of the crystal. This 'Michelson fringe' interpretation is supported by the observed steady movement across the output beam of the interference fringes produced by a refractive wedge when the piezo voltage was ramped. The front-mirror displacement required for one complete fringe at the given wavelength is only 0.675 A; therefore, a quiet environment is vital for operating this device, as previous experiments have shown.

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PubMed2003

A holographic approach to point defect structure determination in inorganic crystals: Er-doped Sc2O3.

A holographic approach to the analysis of a Bragg scattering pattern has been described by Szöke [Acta Cryst. (1993), A49, 853-866]. The combination of crystallographic procedures and holographic interpretation allows reconstruction of an unknown part of the crystalline structure model-free if the other part of the structure is known. By introducing the concept of an average crystal, this approach is extended to point defect structures in inorganic crystals. In this case, the host lattice is well known while the defect structure is regarded as the unknown part. To demonstrate the feasibility of this approach, an Sc(2)O(3) sample doped with Er at low concentration has been studied. An additional electron density has been observed, which can be interpreted as an interstitial Er position.

Journal Article↗
PubMed2002

Silicon drift detectors as a tool for time-resolved fluorescence XAFS on low-concentrated samples in catalysis.

A silicon drift detector (SDD) was used for ex situ and time-resolved in situ fluorescence X-ray absorption fine structure (XAFS) on low-concentrated catalyst samples. For a single-element and a seven-element SDD the energy resolution and the peak-to-background ratio were verified at high count rates, sufficient for fluorescence XAFS. An experimental set-up including the seven-element SDD without any cooling and an in situ cell with gas supply and on-line gas analysis was developed. With this set-up the reduction and oxidation of a zeolite supported catalyst containing 0.3 wt% platinum was followed by fluorescence near-edge scans with a time resolution of 10 min each. From ex situ experiments on low-concentrated platinum- and gold-based catalysts fluorescence XAFS scans could be obtained with sufficient statistical quality for a quantitative analysis. Structural information on the gold and platinum particles could be extracted by both the Fourier transforms and the near-edge region of the XAFS spectra. Moreover, it was found that with the seven-element SDD concentrations of the element of interest as low as 100 ppm can be examined by fluorescence XAFS.

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