Exploring oxygen diffusion mechanisms in Pr2NiO4+d under in situ conditions by neutron scattering: interplay between structure and lattice dynamics
Experimental Condensed Matter Physics
Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials
Final Report Abstract
In the French-German project ExODiff, the influence of oxygen order and lattice dynamics on the enhancement of oxygen mobility at low temperatures was studied in various Ruddlesden- Popper phases, especially in K2NiF4-type oxides, in order to better understand the diffusion mechanism and the resulting concepts for the design and optimization of new oxygen ion conductors (and thus their potential for numerous applications, as in the energy sector or in catalysis). The samples for the project were grown and characterized by the French project partner (ICGM, Montpellier) using an optimized floating zone melting process. Both partners wanted to provide the experimental methods for further investigations of the structural details of the charge, oxygen and spin order depending on temperature and excess oxygen on their sites or apply for them at other institutions, in particular for diffraction and spectroscopy with synchrotron (at the ESRF). or neutron radiation (at FRM II). However, the Covid-19 pandemic and the failure of the FRM II neutron source despite several attempts to relaunch it forced us to adjust the planned process. In addition to measurements on Pr2NiO4+δ, also those of Nd2NiO4±δ and La2CoO4+δ grown at the ICGM were considered, which were not part of the original project and measured elsewhere in order to provide a more comprehensive picture of the complex interplay of different oxygen concentrations and the various structural properties in these compounds. A first important finding is that the Pr and Nd compounds with maximum oxygen excess (δmax=0.25) reach an equilibrium state of δ~0.23 after storage under ambient conditions for several months. The high oxygen mobility allows a return to δmax at moderate temperatures (e.g. with Nd2NiO4.23 at approx. 630K). With La2CoO4+δ, the threshold for spontaneous oxygen uptake is only just above room temperature. In addition, the growth of large La2CoO4.25 single crystals for neutron studies of the oxygen order was successful for the first time. Synchrotron measurements on the RP compounds with large δ reveal small but measurable deviations from their structures generally described as orthorhombic or tetragonal over wide temperature ranges. They are described as long-range monoclinic modulations up to ~100 Å. Neutron diffraction also shows these at low δ and low T, where they correlate with the magnetic structure (e.g. Nd2NiO4.10). Recently, Pr2NiO4+δ and La2CoO4+δ samples with adjacent domains with perfect stoichiometry and excess oxygen were successfully prepared. Their sizes and volume proportions can be tuned in a targeted manner. This means that the influence of oxygen uptake on charge, spin order, etc. can be specifically studied not only locally and over long range scale but also on the intermediate length scale and in terms of the influence on and from grain boundaries.
Publications
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Interdependent scaling of long-range oxygen and magnetic ordering in non-stoichiometric Nd2NiO4.10; MLZ Usermeeting and German Conference on Neutron Scattering 2020, Garching, Dec. 8th – 10th 2020
W. Paulus, S.R. Maity, M. Ceretti, L. Keller, J. Schefer & M. Meven
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Infrared furnace for in situ neutron single-crystal diffraction studies in controlled gas atmospheres at high temperatures. Journal of Applied Crystallography, 54(3), 822-829.
Magro, Fernando; Ceretti, Monica; Meven, Martin & Paulus, Werner
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Growth and Oxygen Stoichiometry Control of High-Quality La2CoO4+δ Single Crystals (δ = 0.25). Crystal Growth & Design, 22(9), 5542-5551.
De Barros, Ruben; Ceretti, Monica; Schmidt, Wolfgang; Pomjakushin, Vladimir Y. & Paulus, Werner
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Overview of research activities at MLZ: Structure Research; French-German Collaboration Workshop (LLB/MLZ), Saclay, Feb. 15th 2022
A. Senyshyn & M. Meven
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Oxygen ion diffusion mechanisms in non-stoichiometric oxides explored by neutron scattering, XXXIII Annual SISN Congress, Milan, Italy, Sep 14th – 16th 2022
M. Ceretti
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Structural complexity in the RP phase La2CoO4+δ explored by synchrotron X-ray single-crystal diffraction and neutron powder diffraction; 33rd European Crystallographic Meeting (ECM33), Versailles, France, Aug 2022
R. de Barros, M. Ceretti, W. Paulus, A. Bosak & V. Nassif
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Unveiling long-range oxygen and electronic order in non-stoichiometric Ruddlesden-Popper oxides Nd2NiO4+δ and La2CoO4+δ by neutron and synchrotron diffraction; thèse pour obtenir le grade du docteur de l’université de Montpellier en Chimie et Physico-chimie des Matériaux (2022), École doctorale Sciences Chimiques Balard
R. de Barros
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Vielfalt und Perspektiven der Einkristalldiffraktion mit heißen Neutronen; „Highlights zu Instrumentierung und Wissenschaft“ on the annual meeting of the MLZ steering committee, Garching, May 23th 2022
M. Meven
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Competitive interplay between long-range oxygen and electronic ordering to promote low-T oxygen mobility in La2CoO4+δ; European Conference on Neutron Scattering (ECNS2023), Garching, March 20th – 23th 2023
W. Paulus, M. Meven, M. Ceretti, R. de Barros & W. Schmidt
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Compounds of rare earths and transition metals: There is always something to discover; JCNS-2 POF V Klausur „Neutrons & Hard Matter – wissenschaftliche Herausforderungen & Beiträge zur Lösung großer gesellschaftlicher Fragestellungen“, GSI, Bonn, April 24 th – 25th 2023
M. Meven
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Exploring low temperature oxygen ion mobility in non-stoichiometric oxides by neutron scattering, FiSMat 2023 - CMD30, Joint Conference, Milan, Italy, Sep 4th – 8th 2023
M. Ceretti
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Growth and characterization of high quality La2CoO4.25 single crystals; International Conference on Crystal Growth and Epitaxy (ICCGE20), Naples, Italy, July 30th – Aug 3rd 2023
M. Ceretti, R. de Barros, W. Paulus, W. Schmidt & V. Pomjakushin
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Large-scale oxygen order phase transitions and fast ordering kinetics at moderate temperatures in Nd2NiO4+δ electrodes. Materials Advances, 4(2), 651-661.
Maity, Sumit Ranjan; Ceretti, Monica; De Barros, Ruben; Keller, Lukas; Schefer, Jürg; Cervellino, Antonio; Rodríguez, Velamazan J. Alberto & Paulus, Werner
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Synthesis and Structural Characterization of Layered Ni+1/+2 Oxides Obtained by Topotactic Oxygen Release on Nd2−xSrxNiO4−δ Single Crystals. Crystals, 13(12), 1670.
Hareesh, Chavana; Ceretti, Monica; Papet, Philippe; Bosak, Alexeï; Meven, Martin & Paulus, Werner
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Single Crystal Diffraction Studies on Energy Storage Materials with Hot Neutrons on HEiDi; MLZ Conference: Neutrons for Energy Storage (NfES), Munich, June 4th -7th 2024
M. Meven, G. Redhammer, D. Rettenwander, M. Ceretti, W. Paulus & A. Bosak
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Single Crystal Diffractometry at the FRM II / MLZ; 9th Meeting of the MLZ Instrumentation Advisory Committee (IAC), Garching, March 12th 2024
M. Meven
