resumo
Effects of calcium doping on the structure, dimensional stability, and mixed oxygen-ion and electron conductivity of perovskite-like La0.5Sr0.5 - xCaxFeO3 - delta(x = 0-0.3) were studied in light of potential membrane applications. The incorporation of relatively small Ca2+ cations into the lanthanum-strontium ferrite lattice decreases unit cell volume, oxygen nonstoichiometry variations and chemical contribution to the thermal expansion in air. These changes correlate with rising tendency to local oxygen-vacancy ordering and the formation of nano-sized domains with the brownmillerite and LaCa2Fe3O8-type lattices, as revealed by electron diffraction. The resultant vacancy trapping, changing domain structure and enlargement of the interfacial boundary area lead to non-linear relationships between the partial ion conductivity and cation composition, while the apparent activation energy for ion transport at temperatures below 900 degrees C remains almost constant, 0.6-0.7 eV. The n-type electron contribution to the total conductivity, measured in the oxygen pressure range 10(-20)-0.5 atm at 700-950 degrees C, is also essentially independent of the calcium concentration. (C) 2013 Elsevier B.V. All rights reserved.
palavras-chave
HIGH-TEMPERATURE TRANSPORT; MIXED CONDUCTIVITY; OXYGEN NONSTOICHIOMETRY; MOSSBAUER-SPECTRA; ION-TRANSPORT; LA1-XSRXFEO3-DELTA; MEMBRANES; FERRITES; EXPANSION; STABILITY
categoria
Chemistry; Physics
autores
Chesnokov, KY; Markov, AA; Patrakeev, MV; Leonidov, IA; Murzakaev, AM; Leonidova, ON; Shalaeva, EV; Kharton, VV; Kozhevnikov, VL
nossos autores
Vladislav Kharton
Investigador Principal CovidadoGrupos