Oxygen Mobility and Surface Reactivity of Ca-Doped Pr2NiO4
21 International Conference on Solid State Ionics
18-23 Jun 2017
conference_type.international conference, Padua
|| Sadykov Vladislav Aleksandrovich
, Pikalova Elena Yurievna
, Kolchugin Alexander Anatolievich
, Eremeev Nikita Fedorovich
, Bogdanovich Nina Mikhajlovna
, Skriabin Pavel Ivanovich
, Krasnov Aleksey
, Sadovskaya Ekaterina Mikhajlovna
, Shmakov Alexander Nikolaevich
, Vinokurov Zakhar
, Ishchenko Arcady Vladimirovich
, Pikalov Sergey
, Fionova Elena
Boreskov Institute of Catalysis SB RAS
Novosibirsk State University
Budker Institute of Nuclear Physics SB RAS
Institute of High Temperature Electrochemistry UB RAS
Ural Federal University named after the first President of Russia B.N.Yeltsin
Institute of Metallurgy, Ural Branch of the Russian Academy of Sciences
Materials with a high mixed ionic-electronic conductivity are required for design of oxygen separation membranes and cathodes of solid oxide fuel cells. Ln2NiO4 oxides with Ruddlesden–Popper (R P) structure are promising materials due to their high oxygen mobility . This work presents results of studies of structural and transport properties of Ca-doped Pr2NiO4.
Pr2 xCaxNiO4 oxides (x=0 0.6) were synthesized by the co-precipitation method and characterized by XRD and TEM. The oxygen mobility for powdered samples was studied by the temperature-programmed oxygen isotope heteroexchange with C18O2 (TPIE) and unit cell volume relaxation after changing pO2.
Up to x=0.5, samples were single-phase R P oxides, while at x=0.6 NiO admixture appears. At increasing x the space group varies in the row Fmmm→I4/mmm→Bbcm with the unit cell volume slightly decreasing. Doping results in enhancement of thermodynamic stability and electrical conductivity, while oxygen mobility decreases. This is explained by decreasing the oxygen excess and hampering cooperative mechanism of diffusion via oxygen migration between interstitial and regular positions . For x>0.3 increasing the lattice anisotropy results in co-existing of 2-3 channels of oxygen diffusion revealed by separate peaks in TPIE curves . A fast diffusion channel (DO~10 8 cm2/s at 700 °C, minor route) corresponds to cooperative mechanism, while slow ones (DO<10 10 cm2/s, main routes) are related to transport in perovskite layers and via interlayer positions near the dopant cation sites. Oxygen mobility and surface reactivity characteristics under the gradient of chemical potential are close to those for previously studied R P oxides .
Support by Russian Science Foundation (Project 16-13-00112), Government of the Russian Federation (Agreement 02.A03.21.0006, Act 211) and shared-access centers “Composition of compounds” and “Ural-M” is gratefully acknowledged.
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