abstract
Previously unexplored oxygen-deficient RuddLesden-Popper Nd2-xSrxNiO4-delta (x = 1.0-1.6) nickelates were evaluated for potential use as oxygen electrode materials for solid oxide fuel and electrolysis ceRs, with emphasis on structural stability, oxygen nonstoichiometry, dimensional changes, and electrical properties. Nd2-xSrxNiO4-delta ceramics possess the K2NiF4-type tetragonal structure under oxidizing conditions at 25-1000 degrees C. Acceptor-type substitution by strontium is compensated by the generation of eLectron-hoLes and oxygen vacancies. Oxygen deficiency increases with temperature and strontium doping reaching -1/8 of oxygen sites for x = 1.6 at 1000 degrees C in air. Strongly anisotropic expansion of the tetragonal Lattice on heating correlated with oxygen nonstoichiometry changes results in an anomalous dilatometric behavior of Nd2-xSrxNiO4-delta ceramics under oxidizing conditions. Moderate thermal expansion coefficients, (11-14) x 10(-6) K-1, ensure however thermomechanical compatibility with common solid electrolytes. Reduction in inert atmosphere induces oxygen vacancy ordering accompanied by a contraction of the Lattice and a decrease of its symmetry to orthorhombic. Nd2-xSrxNiO4-delta ceramics exhibit a p-type metallic-Like electrical conductivity at 500-1000 degrees C under oxidizing conditions, with the highest conductivity (290 S cm(-1) at 900 degrees C in air) observed for x = 1.2. The high Lev& of oxygen deficiency in Sr-rich Nd2-xSrxNiO4 impLies enhanced mixed ionic-electronic transport favorable for electrode applications.
keywords
OXIDE FUEL-CELLS; NEGATIVE THERMAL-EXPANSION; TRANSPORT-PROPERTIES; CRYSTAL-STRUCTURE; ELECTROCHEMICAL PROPERTIES; MAGNETIC-PROPERTIES; STRUCTURAL-CHANGES; PARTIAL-PRESSURE; ND2-XSRXNIO4+DELTA; NICKELATE
subject category
Chemistry; Energy & Fuels; Materials Science
authors
Kravchenko, E; Khalyavin, D; Zakharchuk, K; Grins, J; Svensson, G; Pankov, V; Yaremchenko, A
our authors
Aleksey Yaremchenko
Principal Researcher
Kiryl Zakharchuk
PhD StudentProjects
acknowledgements
This work was developed within the project IF/01072/2013/CP1162/CT0001 and project CICECO-Aveiro Institute of Materials (ref. UID/CTM/50011/2013) financed by national funds through the FCT/MEC and when applicable co-financed by FEDER under the PT2020 Partnership Agreement. Ekaterina Kravchenko gratefully acknowledges the doctoral grant (Belarusian State University) and Visby Programme scholarship (Swedish Institute). Authors are thankful to Alexandre Viskup (RI PCP BSU) and Dr Aliaksandr Shaula (TEMA/UA) for experimental assistance.