Síntese hidrotermal assistida por micro-ondas de Ce1-xGdxO2-δ e caracterização visando sua aplicação como eletrólitos de SOFC

Abstract

Fuel cell electrolytes require high operating temperatures, resulting in high operating and manufacturing costs. Materials based on rare earth doped ceria are an alternative, as they have higher electrical conductivity than zirconia-yttria at lower operating temperatures. However, some difficulties remain unresolved in obtaining ceria-based solid electrolytes, such as the low sinterability of the material and the low conductivity of grain boundaries, usually associated with the presence of impurities. In this context, the present work presents the study of microwave-assisted hydrothermal synthesis as a synthesis method to obtain Ce1-xGdxO2-δ nanoparticles, and to associate the characteristics of the powders obtained with compatible characteristics for their use as electrolytes SOFC. Samples of Ce1-xGdxO2-δ (x = 0.1, 0.2 and 0.3) were synthesized, with hydrothermal treatment time variation (15, 30, 45 and 60 minutes). The obtained materials were characterized by density measurements, FRX, XRD, TG, BET, SEMFEG, TEM and impedance spectroscopy. The results showed that shorter hydrothermal processing times result in nanometer powders with smaller particle sizes, high specific surface area, and strong tendency to agglomeration state, which directly influences the densification of the obtained materials. Despite the introduction of Gd into the cerium oxide network, all powders crystallized into the fluorite-like structure of ceria. The impedance spectroscopy results indicate that the increase of the dopant concentration decreases the grain conductivity, due to the increased interaction of doping defects, and that the impurities presented act as ionic blockingagents.