Oxygen Nonstoichiometry, Mixed Conductivity, and Mossbauer Spectra of Ln(0.5)A(0.5)FeO(3-delta) (Ln = La-Sm, A = Sr, Ba): Effects of Cation Size

authors	Kharton, VV; Kovalevsk, AV; Patrakeev, MV; Tsipis, EV; Viskup, AP; Kolotygin, VA; Yaremchenko, AA; Shaula, AL; Kiselev, EA; Waerenborgh, JC
nationality	International
journal	CHEMISTRY OF MATERIALS
keywords	PEROVSKITE-TYPE OXIDES; TRANSPORT-PROPERTIES; THERMAL-EXPANSION; FUEL-CELLS; IONIC-CONDUCTIVITY; LANTHANUM FERRITE; CATHODE MATERIALS; SOFC CATHODES; LA1-XSRXFEO3-DELTA; PERMEABILITY
abstract	Increasing the difference of the Ln(3+) and A(2+) cation radii in perovskite-type Ln(0.5)A(0.5)FeO(3-delta)) (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 Mossbauer spectra of oxygen-stoichiometric Ln(0.5)A(0.5)FeO(3). 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 Ln(3+) size in Ln(0.5)Sr(0.5)FeO(3-delta) series. The n-type electronic conduction and low-p(O-2) stability at 1223 K are Substantially unaffected by the cation radius mismatch.
publisher	AMER CHEMICAL SOC
issn	0897-4756
year published	2008
volume	20
issue	20
beginning page	6457
ending page	6467
digital object identifier (doi)	10.1021/cm801569j
web of science category	Chemistry, Physical; Materials Science, Multidisciplinary
subject category	Chemistry; Materials Science
unique article identifier	WOS:000260254400029