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Application of synchrotron through-the-substrate microdiffraction to crystals in polished thin sections.

Rius J, Vallcorba O, Frontera C, Peral I, Crespi A, Miravitlles C - IUCrJ (2015)

Bottom Line: Its viability for crystal structure solution by Patterson function direct methods (δ recycling) and for accurate single-crystal least-squares refinements is demonstrated with some representative examples from petrology in which different glass substrate thicknesses have been employed.The section of the crystal microvolume must be at least of the same order of magnitude as the focus of the beam (15 × 15 µm in the provided examples).Thanks to its versatility and experimental simplicity, this method-ology should be useful for disciplines as disparate as petrology, materials science and cultural heritage.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institut de Ciència de Materials de Barcelona, CSIC, Campus de la Universitat Autònoma de Barcelona, Bellaterra, Catalonia 08193, Spain.

ABSTRACT
The synchrotron through-the-substrate X-ray microdiffraction technique (tts-μXRD) is extended to the structural study of microvolumes of crystals embedded in polished thin sections of compact materials [Rius, Labrador, Crespi, Frontera, Vallcorba & Melgarejo (2011 ▸). J.Synchrotron Rad. 18, 891-898]. The resulting tts-μXRD procedure includes some basic steps: (i) collection of a limited number of consecutive two-dimensional patterns (frames) for each randomly oriented crystal microvolume; (ii) refinement of the metric from the one-dimensional diffraction pattern which results from circularly averaging the sum of collected frames; (iii) determination of the reciprocal lattice orientation of each randomly oriented crystal microvolume which allows assigning the hkl indices to the spots and, consequently, merging the intensities of the different frames into a single-crystal data set (frame merging); and (iv) merging of the individual crystal data sets (multicrystal merging) to produce an extended data set suitable for structure refinement/solution. Its viability for crystal structure solution by Patterson function direct methods (δ recycling) and for accurate single-crystal least-squares refinements is demonstrated with some representative examples from petrology in which different glass substrate thicknesses have been employed. The section of the crystal microvolume must be at least of the same order of magnitude as the focus of the beam (15 × 15 µm in the provided examples). Thanks to its versatility and experimental simplicity, this method-ology should be useful for disciplines as disparate as petrology, materials science and cultural heritage.

No MeSH data available.


Related in: MedlinePlus

Setups for selecting target points on polished thin sections. Off-axis: (left) the sample visualization system is placed perpendicular to the thin section surface and the target points are searched on the xy plane; (right) before data collection the thin section is placed normal to the incoming beam, and the diffraction pattern is collected by rotating the thin section around the ϕ tilt axis (dark part = thin section, light part = glass substrate). On-axis: (left) the visualization system is along the beam axis and the target points are searched on the xz plane; (right) before data collection the system is removed, and in this case the diffraction pattern is collected by rotating the thin section around the vertical ϕ tilt axis. The number of collected spots can be increased by an additional collection with the thin section rotated by Δχ = 90° around the axis defined by the beam.
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fig1: Setups for selecting target points on polished thin sections. Off-axis: (left) the sample visualization system is placed perpendicular to the thin section surface and the target points are searched on the xy plane; (right) before data collection the thin section is placed normal to the incoming beam, and the diffraction pattern is collected by rotating the thin section around the ϕ tilt axis (dark part = thin section, light part = glass substrate). On-axis: (left) the visualization system is along the beam axis and the target points are searched on the xz plane; (right) before data collection the system is removed, and in this case the diffraction pattern is collected by rotating the thin section around the vertical ϕ tilt axis. The number of collected spots can be increased by an additional collection with the thin section rotated by Δχ = 90° around the axis defined by the beam.

Mentions: The application of tts-μXRD requires attention to various practical aspects. Since part of the attractiveness of the technique is the easy access to selected points on the thin section, a clear and detailed visualization system is most important. As already mentioned by Rius et al. (2011 ▸), one very convenient solution used at the synchrotron beamline BM16 (ESRF, Grenoble, France) is to put the sample visualization system normal to the surface of the thin section, as indicated in Fig. 1 ▸ (off-axis). This enables the user to find the target point by shifting the sample horizontally. Before data collection, the thin section is rotated by 90° to position it normal to the beam (with the substrate placed between the thin section and the incoming beam). A second solution is simply to place the visualization system along the beam axis (on-axis), so that posterior rotation by 90° around the tilt axis is no longer necessary (Fig. 1 ▸). However, the substrate must be transparent, otherwise the target point cannot easily be found. Placing the thin section between the substrate and the incoming beam is not advisable, since intensities diffracted at high angles travel further inside the substrate and will be affected more by absorption. This contributes to an increase in the number of unobserved reflections.


Application of synchrotron through-the-substrate microdiffraction to crystals in polished thin sections.

Rius J, Vallcorba O, Frontera C, Peral I, Crespi A, Miravitlles C - IUCrJ (2015)

Setups for selecting target points on polished thin sections. Off-axis: (left) the sample visualization system is placed perpendicular to the thin section surface and the target points are searched on the xy plane; (right) before data collection the thin section is placed normal to the incoming beam, and the diffraction pattern is collected by rotating the thin section around the ϕ tilt axis (dark part = thin section, light part = glass substrate). On-axis: (left) the visualization system is along the beam axis and the target points are searched on the xz plane; (right) before data collection the system is removed, and in this case the diffraction pattern is collected by rotating the thin section around the vertical ϕ tilt axis. The number of collected spots can be increased by an additional collection with the thin section rotated by Δχ = 90° around the axis defined by the beam.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4491317&req=5

fig1: Setups for selecting target points on polished thin sections. Off-axis: (left) the sample visualization system is placed perpendicular to the thin section surface and the target points are searched on the xy plane; (right) before data collection the thin section is placed normal to the incoming beam, and the diffraction pattern is collected by rotating the thin section around the ϕ tilt axis (dark part = thin section, light part = glass substrate). On-axis: (left) the visualization system is along the beam axis and the target points are searched on the xz plane; (right) before data collection the system is removed, and in this case the diffraction pattern is collected by rotating the thin section around the vertical ϕ tilt axis. The number of collected spots can be increased by an additional collection with the thin section rotated by Δχ = 90° around the axis defined by the beam.
Mentions: The application of tts-μXRD requires attention to various practical aspects. Since part of the attractiveness of the technique is the easy access to selected points on the thin section, a clear and detailed visualization system is most important. As already mentioned by Rius et al. (2011 ▸), one very convenient solution used at the synchrotron beamline BM16 (ESRF, Grenoble, France) is to put the sample visualization system normal to the surface of the thin section, as indicated in Fig. 1 ▸ (off-axis). This enables the user to find the target point by shifting the sample horizontally. Before data collection, the thin section is rotated by 90° to position it normal to the beam (with the substrate placed between the thin section and the incoming beam). A second solution is simply to place the visualization system along the beam axis (on-axis), so that posterior rotation by 90° around the tilt axis is no longer necessary (Fig. 1 ▸). However, the substrate must be transparent, otherwise the target point cannot easily be found. Placing the thin section between the substrate and the incoming beam is not advisable, since intensities diffracted at high angles travel further inside the substrate and will be affected more by absorption. This contributes to an increase in the number of unobserved reflections.

Bottom Line: Its viability for crystal structure solution by Patterson function direct methods (δ recycling) and for accurate single-crystal least-squares refinements is demonstrated with some representative examples from petrology in which different glass substrate thicknesses have been employed.The section of the crystal microvolume must be at least of the same order of magnitude as the focus of the beam (15 × 15 µm in the provided examples).Thanks to its versatility and experimental simplicity, this method-ology should be useful for disciplines as disparate as petrology, materials science and cultural heritage.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institut de Ciència de Materials de Barcelona, CSIC, Campus de la Universitat Autònoma de Barcelona, Bellaterra, Catalonia 08193, Spain.

ABSTRACT
The synchrotron through-the-substrate X-ray microdiffraction technique (tts-μXRD) is extended to the structural study of microvolumes of crystals embedded in polished thin sections of compact materials [Rius, Labrador, Crespi, Frontera, Vallcorba & Melgarejo (2011 ▸). J.Synchrotron Rad. 18, 891-898]. The resulting tts-μXRD procedure includes some basic steps: (i) collection of a limited number of consecutive two-dimensional patterns (frames) for each randomly oriented crystal microvolume; (ii) refinement of the metric from the one-dimensional diffraction pattern which results from circularly averaging the sum of collected frames; (iii) determination of the reciprocal lattice orientation of each randomly oriented crystal microvolume which allows assigning the hkl indices to the spots and, consequently, merging the intensities of the different frames into a single-crystal data set (frame merging); and (iv) merging of the individual crystal data sets (multicrystal merging) to produce an extended data set suitable for structure refinement/solution. Its viability for crystal structure solution by Patterson function direct methods (δ recycling) and for accurate single-crystal least-squares refinements is demonstrated with some representative examples from petrology in which different glass substrate thicknesses have been employed. The section of the crystal microvolume must be at least of the same order of magnitude as the focus of the beam (15 × 15 µm in the provided examples). Thanks to its versatility and experimental simplicity, this method-ology should be useful for disciplines as disparate as petrology, materials science and cultural heritage.

No MeSH data available.


Related in: MedlinePlus