abstract
Increasing Sr2+ concentration and the creation of A-site deficiency in La1-x-ySrxCoO3-delta (x = 0.3-0.7, y = 0-0.05) increase oxygen ionic conductivity, oxygen permeability of the dense ceramic membranes, and surface exchange limitations, in correlation with the oxygen nonstoichiometry variations. Regression analysis of the experimental data on oxygen deficiency and steady-state oxygen permeation fluxes demonstrated an important role of the defect association processes, namely, clustering of the oxygen vacancies and Co2+. The X-ray diffraction and Mossbauer spectroscopy studies of model Fe-57-doped composition, (La0.3Sr0.7Co0.99Fe0.01O3-delta)-Fe-57, confirmed that the ordering processes occur on reduction. In the case of La0.5Sr05CoO3-delta when oxygen transport limitations by bulk ionic conduction and surface exchange are comparable, the exchange limitations are located essentially at the membrane permeate-side surface. Reducing p(O-2) and temperature leads to greater surface limitations. The chemically induced lattice expansion increases with increasing both x and y in La1-x-ySrxCoO3-delta, as well as with increasing temperature. The apparent thermal expansion coefficients calculated from the dilatometric data in air vary from (16-17) x 10(-6) K-1 at 300-950 K up to (28-31) x 10(-6) K-1 at 750-1370 K.
keywords
MIXED CONDUCTIVITY; OXYGEN NONSTOICHIOMETRY; MOSSBAUER-SPECTRA; COBALTITE CATALYSTS; LA1-XSRXCOO3-DELTA; THERMODYNAMICS; PERMEATION; MECHANISMS; EXPANSION; EXCHANGE
subject category
Electrochemistry
authors
Tsipis, EV; Naumovich, EN; Patrakeev, MV; Yaremchenko, AA; Kovalevsky, AV; Waerenborgh, JC; Kharton, VV
our authors
Aleksey Yaremchenko
Principal Researcher
Andrei Kavaleuski
Principal Researcher
Vladislav Kharton
Invited Principal Researcheracknowledgements
The work of ISSP RAS team centered on the synthesis and electrochemical measurements was supported by the Russian Science Foundation (grant 20-19-00478). E.N. Naumovich received financial support from the Ministry of Science and Higher Education of the Republic of Poland for Statutory Grant CPE/001/STAT/20 in the Institute of Power Engineering. A.A. Yaremchenko and A.V. Kovalevsky received financial support within the project CICECO-Aveiro Institute of Materials (UIDB/50011/2020 and UIDP/50011/2020) financed by national funds through the FCT/MCTES and when appropriate cofinanced by FEDER under the PT2020 Partnership Agreement. J.C. Waerenborgh also received support from the FCT (Portugal) under the contract UID/Multi/04349/2013.