International
Tables for
Crystallography
Volume H
Powder diffraction
Edited by C. J. Gilmore, J. A. Kaduk and H. Schenk

International Tables for Crystallography (2018). Vol. H, ch. 2.9, pp. 195-196

Section 2.9.3.4.1. Introduction

W. van Beeka* and P. Pattisona,b

aSwiss–Norwegian Beamlines at ESRF, CS 40220, 38043 Grenoble CEDEX 9, France, and bLaboratory for Quantum Magnetism, Institute of Physics, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne, Switzerland
Correspondence e-mail:  wouter@esrf.fr

2.9.3.4.1. Introduction

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The special characteristics of neutrons imply both advantages and challenges for the design of in situ experiments and their associated equipment. The differences in penetration depths between X-rays and neutrons and the correspondingly smaller scattering cross sections for neutrons, together with the much lower flux densities, imply that cells for neutrons are quite different from the miniature capillary cells for X-rays described in the previous sections. Above all, the sample volume is by necessity often much larger than the equivalent volume required for a laboratory X-ray or synchrotron experiment. However, the ability of neutrons to penetrate deep into sample environments has been of great importance for studying samples at very low temperature, under high pressure or within strong magnetic fields. Similarly, reaction cells for in situ investigations profit from the ability of neutrons to penetrate through thick-walled vessels, for example for studying gas–solid reactions under high pressure. Only relatively recently, with the availability of high-energy synchrotron beamlines (>100 keV), can X-rays effectively compete with neutrons in this domain. Even in these cases, the very different scattering properties of neutrons (e.g. the strong variation of cross section with isotope) means that some measurements that are challenging, if not impossible, with X-rays can become quite feasible with neutrons. The solid–gas reaction of intermetallic phases with H2 gas is a good example, where the positions of the interstitial H atoms can be located within a heavy-metal hydride (Kamazawa et al., 2013[link]). Similarly, the hydration of cement has been investigated many times, with improved time resolution resulting from developments in neutron optics and detector performance. In situ studies of oxidation reactions have also benefited from the better ability of neutrons to determine the atomic positions of oxygen during synthesis (Bianchini et al., 2013[link]). The investigation of chemical processes in the electrodes of batteries has, for example, been particularly fruitful. Once again, specialist cells for electrochemistry have been developed that take advantage of the penetration power of the neutrons in order to reveal bulk behaviour within the electrode material. Examples of these and other applications are given in an extensive review of in situ and time-resolved neutron scattering (Isnard, 2007[link]) and in the more recent articles by Hansen & Kohlmann (2014[link]), Sharma et al. (2015[link]) and Pang & Peterson (2015[link]). It should also be noted that different geometrical arrangements are used in angular-dispersive monochromatic neutron diffraction or when using a fixed-angle detector bank for time-of-flight neutron diffraction, which can have important implications for the cell design. In the following sections, we will examine some of these specialist cells in more detail.

References

Bianchini, M., Leriche, J. B., Laborier, J.-L., Gendrin, L., Suard, E., Croguennec, L. & Masquelier, C. (2013). A new null matrix electrochemical cell for Rietveld refinements of in-situ or operando neutron powder diffraction data. J. Electrochem. Soc. 160, A2176–A2183.Google Scholar
Hansen, T. C. & Kohlmann, H. (2014). Chemical reactions followed by in situ neutron powder diffraction. Z. Anorg. Allg. Chem. 640, 3044–3063.Google Scholar
Isnard, O. (2007). A review of in situ and/or time resolved neutron scattering. C. R. Phys. 8, 789–805.Google Scholar
Kamazawa, K., Aoki, M., Noritake, T., Miwa, K., Sugiyama, J., Towata, S., Ishikiriyama, M., Callear, S. K., Jones, M. O. & David, W. I. F. (2013). In-operando neutron diffraction studies of transition metal hydrogen storage materials. Adv. Energ. Mater. 3, 39–42.Google Scholar
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Sharma, N., Pang, W. K., Guo, Z. & Peterson, V. K. (2015). In situ powder diffraction studies of electrode materials in rechargeable batteries. ChemSusChem, 8, 2826–2853.Google Scholar








































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