oxygen mobility; electronic and structural correlations; structural disorder; low-temperature reactivity; transition metal oxides
Dutta Rajesh, Maity Avishek, Marsicano Anna, Ceretti Monica, Chernyshov Dmitry, Bosak Alexeï, Villesuzanne Antoine, Roth Georg, Perversi Giuditta, Paulus Werner (2020), Long-range oxygen ordering linked to topotactic oxygen release in Pr2NiO4+d fuel cell cathode material, in Journal of Materials Chemistry A
Maity Sumit Ranjan, Ceretti Monica, Keller Lukas, Schefer Jürg, Shang Tian, Pomjakushina Ekaterina, Meven Martin, Sheptyakov Denis, Cervellino Antonio, Paulus Werner (2019), Structural disorder and magnetic correlations driven by oxygen doping in Nd2NiO4+δ ( δ∼0.11 ), in Physical Review Materials
, 3(8), 083604-083604.
Maity Sumit Ranjan, Keller Lukas, Schefer Juerg, Ceretti Monica, Paulus Werner (2018), Neutron diffraction studies of oxygen disorder in Nd 2 NiO 4+ d, in Acta Crystallographica Section A Foundations and Advances
, 74(a2), e69-e70.
Ceretti Monica, Wahyudi Olivia, André Gilles, Meven Martin, Villesuzanne Antoine, Paulus Werner (2018), (Nd/Pr) 2 NiO 4+δ : Reaction Intermediates and Redox Behavior Explored by in Situ Neutron Powder Diffraction during Electrochemical Oxygen Intercalation, in Inorganic Chemistry
, 57(8), 4657-4666.
Maity Sumit Ranjan, Schefer Juerg, Keller Lukas, Ceretti Monica, Paulus Werner (2017), Neutron diffraction studies of oxygen disorder in Nd 2 NiO 4+ d, in Acta Crystallographica Section A Foundations and Advances
, 73(a2), C1426-C1426.
Maity Sumit R., Ceretti Monica, Meven Martin, Schefer Jurg, Keller Lukas, Petry Winfried, Paulus Werner (2016), Temperature dependent structural studies of the oxygen ion conductor Pr 1.5 Sr 0.5 NiO 4+d investigated by single crystal neutron diffraction, in Acta Crystallographica Section A Foundations and Advances
, 72(a1), s287-s287.
We propose to study complex ordering phenomena and associated changes in the physical and chemical properties in non-stoichiometric oxides using a low temperature electrochemical reaction to control the oxygen content in two related structure families: Brownmillerites, which are oxygen deficient Perovskites and Ruddlesden-Popper phases with K2NiF4-type structure. These compounds are complex due to the many active degrees of freedom such as charge, spin and orbital ordering, which interact in a competitive, synergetic way. The principal aim of this proposal is to explore the limits of structural correlations and associated phase diagrams for selected Ruddlesden-Popper (R2MO4 , R = La, Nd, Pr,…, M = Cu, Ni, Co,…) and Brownmillerite type oxides (Sr2(Fe/Co)O5), and to explore to which extend they are homogeneous. On the other hand these giant correlations have not only structural implications (for example, La2CoO4.25 yields strong correlations with a unit cell volume of 25.000 Å3, Pr2NiO4.25 exceeds this quantity by far with 3.000.000 Å3), but consequently imply electronic ordering and lattice dynamical properties. Beside electronic correlations, lattice dynamics is here of special interest, as we were able to recently evidence for both oxide families phonon assisted oxygen diffusion activated already at ambient temperature. Thus, structural instabilities and associated creation of low energy phonon modes is assumed to be a prerequisite for low temperature oxygen diffusion in these types of frameworks. Correlated phonon modes create large displacement amplitudes of oxygen atoms and generate oxygen diffusion pathways with shallow activation energies thus become another important issue in these strongly correlated electronic systems. Structural, electronic and lattice dynamical correlations will be explored via a multi-technical approach combining structure and dynamic studies importantly carried out under in in situ conditions during oxygen intercalation reactions in especially constructed electrochemical cells taking care of complementary advantages of synchrotron radiation (diffraction, inelastic X-ray scattering, XAFS, soft resonance scattering) and neutron scattering techniques (diffraction, spectroscopy). The specific approach here is that an important part of proposed experiments will be carried out in-situ on single crystals. The feasibility of these types of studies has already been successfully demonstrated. The better understanding of the mechanisms allowing low temperature oxygen ion mobility in solid oxides is of fundamental and applied interest, as for the development and conception of oxygen membranes in solid oxide fuel cells (SOFC), sensors or electro-catalysts.We submit this research proposal under the lead agency process between the SNF and the ANR with the intention to maximize the efficiency in the research of non-stoichiometric oxides at the Paul Scherrer Institut (PSI) and the University of Montpellier (UM). The institutes complement each other perfectly with the resources on large scale facility research (µSR, Synchrotron radiation and Neutron source) at the PSI and the facilities for single crystal synthesis and electrochemistry at the University of Montpellier, France.