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| Hauptseite > Publikationsdatenbank > Infrared furnace for in situ neutron single-crystal diffraction studies in controlled gas atmospheres at high temperatures |
| Hauptseite > Publikationsdatenbank > Infrared furnace for in situ neutron single-crystal diffraction studies in controlled gas atmospheres at high temperatures |
| Journal Article | FZJ-2021-05253 |
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2021
Wiley-Blackwell
[S.l.]
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Please use a persistent id in citations: http://hdl.handle.net/2128/29876 doi:10.1107/S1600576721003198
Abstract: For the understanding of oxygen diffusion mechanisms in non-stoichiometric oxides, the possibility to explore structural changes as a function of the oxygen partial pressure with temperature and related oxygen bulk stoichiometry is mandatory. We report here on the realization of a high temperature furnace, suitable for single crystal neutron diffraction, working continuously at temperatures up to 1000°C at different and adjustable partial gas pressures up to 2 bars. This allows to explore the phase diagrams of non-stoichiometric oxides under in operando conditions under controlled oxygen partial pressure. As a pilot study we explored the structural changes of Pr$_2$NiO$_{4+\delta}$ at room temperature ($\delta$ ≈ 0.24), and at 900°C under 1 bar P(O2) ($\delta$ ≈ 0.13) as well as under secondary vacuum (approximately 10$^{-5}$ mbar) condition yielding a $\delta$ close to zero. The strong anharmonic displacements of the apical oxygen atoms along the [110] shallow diffusion pathway, which were previously observed at RT and 400°C, clearly become more isotropic at 900°C. Our study evidences that the anisotropic oxygen displacements, here related to lattice instabilities, play a major role to understand oxygen diffusion pathways and related activation energies at moderate temperatures. This also shows the importance of the availability of such reaction cells for single crystal neutron diffraction to explore the phase diagram and associated structural changes of non-stoichiometric oxygen ion conductors and respective diffusion mechanisms.
Keyword(s): Chemical Reactions and Advanced Materials (1st) ; Instrument and Method Development (2nd) ; Chemistry (2nd) ; Crystallography (2nd)
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