Lanthanum gallate with partial substitutions for strontium and magnesium shows higher ionic conductivity than traditional ionic conductors such as yttria-stabilized zirconia (8YSZ), and has been considered for application as solid electrolyte and electrode in Solid Oxide Fuel Cells operating at intermediate temperatures (500-700ºC). Parallel to the development of new solid electrolytes, improvement of the already known electrolytes has been one goal. In this work, the effects of adding 8YSZ to La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3-δ (LSGM), on the microstructure and electrical performance were investigated. Compound electrolytes consisting of up to 20 wt.% 8YSZ were prepared by solid state reactions. Sintered pellets with up to 10 wt.% 8YSZ achieved near full density after sintering at 1450ºC and reduction in the fraction of impurity phases. Addition of 8YSZ promoted grain growth to LSGM. The higher ionic conductivity was obtained for 1 wt.% 8YSZ addition with slight decrease of the apparent activation energy.

Doped lanthanum gallate constitutes a family of solid electrolytes with high ionic conductivity, wide electrolytic domain, and good chemical stability. The combination of its properties turns some compounds of this family promising candidates for application in solid oxide cells operating at intermediate temperatures. In this work, La0.9Sr0.1Ga0.8Mg0.2O3-y - xLa1.55Sr0.45Ga3O7+δ with x = 0, 1, and 5 wt.% were investigated aiming to obtain a composite solid electrolyte with optimized properties compared to the parent material. Composite electrolytes were prepared by solid state reaction method and evaluated for densification, phase content, and microstructure. Electrical conductivity measurements were carried out as a function of temperature and oxygen partial pressure. Increase on densification and structural homogeneity were obtained with increasing fraction of the melilite phase. The electrical conductivity determined by impedance spectroscopy revealed a decrease of the bulk resistivity for increasing amounts of La1.55Sr0.45Ga3O7+δ.

Gostaria de agradecer primeiramente a Dra. Eliana Navarro dos Santos Muccillo pela orientação, ensinamentos, dedicação desde a iniciação científica.Ao CNPq pela bolsa concedida para realização deste trabalho (Processo n.

Doped lanthanum gallate constitutes a family of solid electrolytes with high ionic conductivity, wide electrolytic domain and good chemical stability. The combination of their properties turns some compounds of this family, promising candidates for application in solid oxide fuel cells operating at intermediate temperatures. In this work, La0.9Sr0.1Ga0.8Mg0.2O3-δ - x La1.55Sr0.45Ga3O7+δ, with x = 0, 1 and 5 wt.% were investigated aiming to obtain a composite solid electrolyte with optimized properties compared to the parent material. Composite electrolytes were prepared by solid state reaction method and evaluated for densification, phase content and microstructure. Electrical conductivity measurements were carried out as a function of temperature and oxygen partial pressure. Increase on densification and microstructural homogeneity were obtained with increasing fraction of the melillite phase. The electrical conductivity determined by impedance spectroscopy revealed a decrease of the grain resistivity for increasing amounts of La1.55Sr0.45Ga3O7+δ.

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