resumo
The structure, microstructure and low-temperature electrical properties of core-shell-type mixed conductors based on lanthanum gallate with Fe-doped grain boundaries are analyzed in depth. Electron probe microanalysis revealed that the iron concentration in the grain-boundary regions (shell) is below 1 at.% and their thickness is no more than 1.5 mu m. The low-temperature (<400 degrees C) electronic conductivity is enhanced by up to 2-3 orders of magnitude with respect to the corresponding undoped ceramics, as revealed by the analysis of impedance spectra combined with microstructural information. The electronic transport numbers lie in the range between 0.35 and 0.1 at 275 to 400 degrees C, decreasing at higher temperatures, where the influence of grain boundaries on the overall transport properties vanishes and the ionic conductivity increases. (C) 2011 Published by Elsevier B.V.
palavras-chave
OXYGEN PERMEATION PROPERTIES; OXIDE FUEL-CELLS; ELECTRICAL-PROPERTIES; LANTHANUM GALLATE; TRANSPORT-PROPERTIES; IONIC-CONDUCTIVITY; MIXED CONDUCTORS; SOLID-SOLUTIONS; MEMBRANES; LAGAO3
categoria
Chemistry; Physics
autores
Gomes, E; Mather, GC; Figueiredo, FM; Marques, FMB
nossos autores
Fernando Manuel Bico Marques
Professor Catedrático
Filipe Miguel H Lebre R Figueiredo
Investigador Principalagradecimentos
Financial support from FCT and PRODEP (Portugal), and CEC (Brussels, Network of Excellence FAME) is greatly appreciated. Prof. Derek Sinclair (U. Sheffield, UK) kindly provided open access to EPMA facilities, with the help of Dr. Cathy Shields.