resumo
A study of the influence of the substitution of Al for Ga in the ceramic processing and electrical properties of La0.95Sr0.05Ga0.90-xAlxMg0.10O3-delta (0 <= x <= 0.3) solid electrolytes is presented. The materials retained orthorhombic symmetry over the entire substitution range, whereas a deviation from Vegard's law for x > 0.20 suggested a maximum Al solubility of x = 0.20. Scanning electron microscopy analysis of ceramic samples revealed that grain growth was inhibited for x >= 0.2. This microstructural change was related to an apparent deterioration of mechanical properties, as suggested by room-temperature Vickers hardness measurements. Impedance spectroscopy revealed a significant degradation of the grain-boundary electrical properties for x >= 0.20, whereas the bulk conductivity was enhanced for 0.10 <= x <= 0.15. Oxygen-permeability measurements confirmed that the studied materials remain essentially pure ionic conductors. An ionic conductivity maximum of 0.047 S/cm at 700 degrees C was obtained for x = 0.10. The effect of aluminium in the grain-bulk ionic conductivity is discussed in terms of defect cluster models and assuming fast oxygen diffusion along domain walls.
palavras-chave
OXIDE-ION CONDUCTOR; MAGNESIUM-DOPED LAGAO3; MECHANICAL-PROPERTIES; THERMAL-EXPANSION; CRYSTAL-STRUCTURE; PHASE-COMPOSITION; PEROVSKITE; STRONTIUM; TEMPERATURE; SR
categoria
Chemistry
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
The authors express their gratitude for financial support from COST Action 525, PRODEP (E. Gomes), FCT (Portugal), and CEC-Brussels (NoE FAME).