High-temperature transport properties, thermal expansion and cathodic performance of Ni-substituted LaSr2MnO2O7-delta

authors	Yaremchenko, AA; Bannikov, DO; Kovalevsky, AV; Cherepanov, VA; Kharton, VV
nationality	International
journal	JOURNAL OF SOLID STATE CHEMISTRY
author keywords	Ruddlesden-popper manganite; Mixed conductor; Oxygen permeability; Solid oxide fuel cell cathode; Seebeck coefficient; Thermal expansion
keywords	MAGNETIC-PROPERTIES; O SYSTEM; ELECTROCHEMICAL-BEHAVIOR; THERMODYNAMIC PROPERTIES; OXYGEN NONSTOICHIOMETRY; PHASE-EQUILIBRIA; OXIDES; CONDUCTIVITY; MAGNETORESISTANCE; STABILITY
abstract	The substitution of manganese with nickel in LaSr2Mn2O7-delta, where the solubility limit corresponds to approximately 25% Mn sites, enhances the Ruddlesden-Popper phase stability at elevated temperatures and atmospheric oxygen pressure. The total conductivity of LaSr2Mn2-yNiyO7-delta (y = 0-0.4) decreases with nickel additions, whilst the average thermal expansion coefficients calculated from dilatometric data in the temperature range 300-1370K increase from (11.4-13.7)x K` at y = 0 up to (12.5-14.4) x 10(-6) K-1 at y = 0.4. The conductivity and Seebeck coefficient of LaSr2Mn1.6CNi0.4O7-delta, analyzed in the oxygen partial pressure range 10(-15)-0.3 atm at 600-1270 K, display that the electronic transport is n-type and occurs via a small polaron mechanism. Reductive decomposition is observed at the oxygen pressures close to Ni/NiO boundary, namely similar to 2.3 x 10(-11) atm at 1223 K. Within the phase stability domain, the electronic transport properties are essentially p(O-2)-independent. The steady-state oxygen permeability of dense LaSr2Mn1.6Ni0.4O7-delta membranes is higher than that of(La,Sr)MnO3-delta, but lower if compared to perovskite-like (Sr,Ce)MnO3-delta. Porous LaSr2Mn1.6Ni0.4O7-delta cathodes in contact with apatite-type La10Si5AlO26.5 solid electrolyte exhibit, however, a relatively poor electrochemical performance, partly associated with strong cation interdiffusion between the materials. (C) 2008 Elsevier Inc. All rights reserved.
publisher	ACADEMIC PRESS INC ELSEVIER SCIENCE
issn	0022-4596
year published	2008
volume	181
issue	11
beginning page	3024
ending page	3032
digital object identifier (doi)	10.1016/j.jssc.2008.07.038
web of science category	Chemistry, Inorganic & Nuclear; Chemistry, Physical
subject category	Chemistry
unique article identifier	WOS:000266250200009