Oxygen deficiency, vacancy clustering and ionic transport in (La,Sr)CoO3-delta

authors	Tsipis, EV; Naumovich, EN; Patrakeev, MV; Yaremchenko, AA; Marozau, IP; Kovalevsky, AV; Waerenborgh, JC; Kharton, VV
nationality	International
journal	SOLID STATE IONICS
author keywords	Lanthanum-strontium cobaltites; Oxygen nonstoichiometry; P(O-2)-T-delta diagrams; Ionic transport; Vacancy clustering; Mossbauer spectroscopy
keywords	LANTHANUM COBALTITES; ELECTRODE MATERIALS; MIXED CONDUCTIVITY; NONSTOICHIOMETRY; LA0.3SR0.7COO3-DELTA; LA1-XSRXCOO3-DELTA; PERMEABILITY; PEROVSKITE; MECHANISMS; EXCHANGE
abstract	The equilibrium p(O-2)-T-delta diagrams of perovskite-type La1-xSrxCoO3-delta (x=0.3-0.7), collected at 873-1223 K in the oxygen partial pressure range 10(-5)-1 atm by coulometric titration and thermogravimetric analysis, were analyzed in order to appraise the effects of the point-defect interactions. The nonstoichiometry variations were adequately described combining the rigid-band approach for delocalized holes and the pair-cluster formation reaction involving oxygen vacancies and Co2+ cations, whilst coulombic repulsion between the positively charged vacancies can be neglected. The resultant relationships between the oxygen chemical potential and mobile vacancy concentration were used for numerical regression analysis of the steady-state oxygen permeation through dense La1-xSrxCoO3-delta membranes, affected by the surface exchange kinetics when Sr2+ content is higher than 40-50%. The calculated ionic conductivity is strongly influenced by the defect association processes, and decreases with decreasing concentration of the mobile vacancies as clustering starts to prevail on reduction. The Mossbauer spectroscopy studies of La1-xSrxCoO3-delta, doped with 1 mol% Fe-57 isotope and moderately reduced at p(O-2)approximate to 10(-5) atm, show no long-range vacancy ordering at x <= 0.5. (C) 2010 Elsevier B.V. All rights reserved.
publisher	ELSEVIER SCIENCE BV
issn	0167-2738
year published	2011
volume	192
issue	1
beginning page	42
ending page	48
digital object identifier (doi)	10.1016/j.ssi.2010.03.029
web of science category	Chemistry, Physical; Physics, Condensed Matter
subject category	Chemistry; Physics
unique article identifier	WOS:000292848800012