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@ARTICLE{Magro:903599,
      author       = {Magro, Fernando and Ceretti, Monica and Meven, Martin and
                      Paulus, Werner},
      title        = {{I}nfrared furnace for in situ neutron single-crystal
                      diffraction studies in controlled gas atmospheres at high
                      temperatures},
      journal      = {Journal of applied crystallography},
      volume       = {54},
      number       = {3},
      issn         = {0021-8898},
      address      = {[S.l.]},
      publisher    = {Wiley-Blackwell},
      reportid     = {FZJ-2021-05253},
      pages        = {822 - 829},
      year         = {2021},
      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.},
      cin          = {JCNS-FRM-II / MLZ / JARA-FIT / JCNS-2 / PGI-4},
      ddc          = {540},
      cid          = {I:(DE-Juel1)JCNS-FRM-II-20110218 / I:(DE-588b)4597118-3 /
                      $I:(DE-82)080009_20140620$ / I:(DE-Juel1)JCNS-2-20110106 /
                      I:(DE-Juel1)PGI-4-20110106},
      pnm          = {6G4 - Jülich Centre for Neutron Research (JCNS) (FZJ)
                      (POF4-6G4) / 632 - Materials – Quantum, Complex and
                      Functional Materials (POF4-632)},
      pid          = {G:(DE-HGF)POF4-6G4 / G:(DE-HGF)POF4-632},
      experiment   = {EXP:(DE-MLZ)HEIDI-20140101},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000659339200011},
      doi          = {10.1107/S1600576721003198},
      url          = {https://juser.fz-juelich.de/record/903599},
}