High-temperature characterization of oxygen-deficient K2NiF4-type Nd2-xSrxNiO4-delta O4-delta (x=1.0-1.6) for potential SOFC/SOEC applications

authors	Kravchenko, E; Khalyavin, D; Zakharchuk, K; Grins, J; Svensson, G; Pankov, V; Yaremchenko, A
nationality	International
journal	JOURNAL OF MATERIALS CHEMISTRY A
keywords	OXIDE FUEL-CELLS; NEGATIVE THERMAL-EXPANSION; TRANSPORT-PROPERTIES; CRYSTAL-STRUCTURE; ELECTROCHEMICAL PROPERTIES; MAGNETIC-PROPERTIES; STRUCTURAL-CHANGES; PARTIAL-PRESSURE; ND2-XSRXNIO4+DELTA; NICKELATE
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.
publisher	ROYAL SOC CHEMISTRY
issn	2050-7488
year published	2015
volume	3
issue	47
beginning page	23852
ending page	23863
digital object identifier (doi)	10.1039/c5ta06779k
web of science category	Chemistry, Physical; Energy & Fuels; Materials Science, Multidisciplinary
subject category	Chemistry; Energy & Fuels; Materials Science
unique article identifier	WOS:000365205000026