Oxygen release from BaLnMn 2 O 6 (Ln: Pr, Nd, Y) under reducing conditions as studied by neutron diffraction Alicja Klimkowicz 1,2, *, Konrad S ´ wierczek 2 , Kun Zheng 2 , Dirk Wallacher 3 , and Akito Takasaki 1 1 Department of Engineering Science and Mechanics, Shibaura Institute of Technology, 3-7-5 Toyosu, Koto-ku, Tokyo 135-8548, Japan 2 Faculty of Energy and Fuels, AGH University of Science and Technology, al. A. Mickiewicza 30, 30-059 Kraków, Poland 3 Sample Environment Department, Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner Platz 1, Berlin, Germany Received: 9 November 2016 Accepted: 2 February 2017 Published online: 13 February 2017 Ó Springer Science+Business Media New York 2017 ABSTRACT Selected A-site cation-ordered BaLnMn 2 O 6 were investigated by neutron diffraction technique in terms of the structural modification ongoing with the oxygen release during annealing in reducing conditions. Kinetics of the struc- tural transformations between oxidized BaLnMn 2 O 6 (O 6 ), partially reduced BaLnMn 2 O 5.5 (O 5.5 ) and fully reduced BaLnMn 2 O 5 (O 5 ) were measured in 200–500 °C range in 5 vol% H 2 in Ar. Studies revealed that both O 6 –O 5.5 and O 5.5 –O 5 transitions for all samples occur according to a two-phase mechanism, but the phases undergo slight modification of their structural parameters. The Y-containing material showed decreased tendency of formation of oxygen vacancy-ordered BaYMn 2 O 5.5 . Moreover, kinetics of the transitions for Pr- and Nd-containing oxides was found to be more constrained by surface reaction and nucleation processes at the initial stage, while the following oxygen release from O 5.5 phase was found to be limited rather by the oxygen diffusion, which is in opposite to BaYMn 2 O 5?d . The obtained results indicate that ionic radius of Ln 3? has a direct influence on the mechanism of the oxygen release process from BaLnMn 2 O 6 , influencing the oxygen storage-related performance. Introduction Oxygen storage materials (OSMs), due to their pos- sible application in many developing technologies, attracted recently a lot of scientific attention [1–5]. Depending on a particular system, the reversible oxygen incorporation/release into/from the material is observed at elevated temperatures (200–700 °C) during oxygen partial pressure (pO 2 ) swing or tem- perature swing with the constant pO 2 . It is therefore considered that various OSMs can be implemented, among others, for inert gas purification; solar water splitting; non-aerobic oxidation including flameless Address correspondence to E-mail: klimkowicz.alicja.ewa.j2@shibaura-it.ac.jp DOI 10.1007/s10853-017-0883-2 J Mater Sci (2017) 52:6476–6485