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Title: Oxygen Nonstoichiometry, Mixed Conductivity, and Mössbauer Spectra of Ln0.5A0.5FeO3−δ (Ln = La−Sm, A = Sr, Ba): Effects of Cation Size
Authors: Kharton, Vladislav V. 
Kovalevsky, Andrei V. 
Patrakeev, Mikhail V. 
Tsipis, Ekaterina V. 
Viskup, Alexandre P. 
Kolotygin, Vladislav A. 
Yaremchenko, Aleksey A. 
Shaula, Aliaksandr L. 
Kiselev, Evgeny A. 
Waerenborgh, João C. 
Issue Date: 28-Oct-2008
Publisher: American Chemical Society
Citation: Chemistry of Materials. 20:20 (2008) 6457-6467
Abstract: Increasing the difference of the Ln3+ and A2+ cation radii in perovskite-type Ln0.5A0.5FeO3−δ (Ln = La, Pr, Nd, Sm; A = Sr, Ba) results in higher oxygen deficiency and lower oxygen-ionic and p-type electronic conductivities, determined using the oxygen permeation and total conductivity measurements at 973−1223 K. The relationships between the anion transport and A-site cation size mismatch remain essentially similar in air and under reducing conditions when most iron cations become trivalent, thus confirming critical influence of oxygen-vacancy trapping processes induced by the lattice strain. At low temperatures, analogous correlation is also observed for quadrupole splittings derived from the Mssbauer spectra of oxygen-stoichiometric Ln0.5A0.5FeO3. Contrary to the ionic conductivity variations, the role of surface exchange kinetics as a permeation-limiting factor, evaluated from the membrane thickness dependence of oxygen fluxes, tends to decrease on Ba2+ doping and on decreasing Ln3+ size in Ln0.5Sr0.5FeO3−δ series. The n-type electronic conduction and low-p(O2) stability at 1223 K are substantially unaffected by the cation radius mismatch.
ISSN: 0897-4756
DOI: 10.1021/cm801569j
Rights: openAccess
Appears in Collections:FCTUC Eng.Mecânica - Artigos em Revistas Internacionais

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