abstract
The electrical properties of a lanthanum gallate solid electrolyte were modified by selectively doping the grain boundaries with Fe. This was achieved by sandwiching a La0.95Sr0.05Ga0.90Mg0.10O3-delta (LSGM) dense pellet between LaFeO3 samples. Annealing at 1550 degrees C in air for several hours promoted Fe diffusion into LSGM via the grain boundaries. Scanning electron microscopy and energy-dispersive spectroscopy analyses showed that iron was located at the grain boundary while the grain bulk preserved the LSGM composition. Impedance spectra obtained at low temperature consist of the two usual bulk and grain boundary contributions. A significant increase in total conductivity was observed for the iron-doped samples, the effect being greater for the grain boundary contribution. The total conductivity measured for the iron-containing material revealed a slight decrease with decreasing oxygen partial pressure, suggesting the onset of p-type electronic conduction. Estimates of the p-type electronic conductivity (6) were obtained by fitting the low temperature impedance spectra to a simple equivalent circuit including one parallel electronic branch. The value for sigma(P) in air at 300 degrees C is 3.1x10(-6) S/cm and the activation energy is 75.1 kJ/mol between 300 and 400 degrees C.
keywords
ELECTROCHEMICAL PERMEABILITY; ELECTRONIC CONDUCTIVITY; MECHANICAL ACTIVATION; OXYGEN PERMEATION; OXIDE; CERAMICS
subject category
Materials Science
authors
Gomes, E; Figueiredo, FM; Marques, FMB
our authors
Fernando Manuel Bico Marques
Full professor