Low-T oxygen diffusion questioning long-range oxygen, electronic and domain ordering in non-stoichiometric Transition Metal Oxides

W. Paulus
ICGM, Univ. Montpellier, CNRS, ENSCM, Montpellier 34293, France
[email protected]

Non-stoichiometric oxides with Ruddlesden-Popper structure type and the chemical formula A2BO4 (A = rare earth, B = transition metal) can uptake extra O-atoms on interstitial lattice sites (Oint). Due to their high mobility even at room temperature, long-range O-ordering up to the sub-mesoscale is observed in several A2BO4+ phases, which, together with charge and spin ordering, results into a competitive interplay for the degree of freedom between structural and electronic ordering. Oxygen ordering thus adds an additional degree of freedom affecting charge and spin ordering, entirely absent in the Sr-doped counterpart A2-xSrxBO4.
On top of structural ordering, we have recently evidenced microstructural ordering by single crystal by synchrotron diffraction to take place during electrochemical red/ox reaction on stand-alone single crystalline electrodes, thereby achieving chemical diffusion coefficient of D* = 6.3 × 10−11 cm2 s−1. Rapid oxygen diffusion becomes possible due to the predominant absence of grain boundaries, as revealed from the evolution of the individual twin domains. For the first time, the formation of anti-phase domains, organized on a length scale of 7 nm, could be evidenced during a chemical reaction, indicated by sharp satellite reflections of the second order. The long-range oxygen ordering phenomena found for Pr2NiO4+δ deliver, together with the ordering processes of the domains, clear evidence for the existence of mesoscopic interactions at both structural and domain levels, thus giving a first meaningful descriptor to better understand what is generally discussed as domain engineering.

References :

[1] Maity, A.; Dutta, R.; Sendtskyi, O.; Ceretti, M.; Lebranchu, A.; Chernyshov, D.; Bosak, A.; Paulus, W. Exploring Fast Room Temperature Oxygen Diffusion in Pr2NiO4+δ Stand-Alone Single-Crystalline Electrodes. Chemistry of Materials 2022, 34, 414-421, doi:10.1021/acs.chemmater.1c03847.
[2] Dutta, R.; Maity, A.; Marsicano, A.; Ceretti, M.; Chernyshov, D.; Bosak, A.; Villesuzanne, A.; Roth, G.; Perversi, G.; Paulus, W. Long-range oxygen ordering linked to topotactic oxygen release in Pr2NiO4+δ fuel cell cathode material. Journal of Materials Chemistry A 2020, 8, 13987-13995, doi:10.1039/D0TA04652C.
[3] Maity, S.R.; Ceretti, M.; Keller, L.; Schefer, J.; Meven, M.; Pomjakushina, E.; Paulus, W. Interdependent scaling of long-range oxygen and magnetic ordering in nonstoichiometric Nd2NiO4.10. Physical Review Materials 2021, 5, 014401, doi:10.1103/PhysRevMaterials.5.014401
[4] Hareesh, C.; Ceretti, M.; Papet, P.; Bosak, A.; Meven, M.; Paulus, W. Synthesis and Structural Characterization of Layered Ni+1/+2 Oxides Obtained by Topotactic Oxygen Release on Nd2-xSrxNiO4-d; Single Crystals. Crystals 2023, 13, 1670, https://doi.org/10.3390/cryst13121670