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Artigo IPEN-doc 24367 Influence of small amounts of gallium oxide addition on ionic conductivity of La0.9Sr0.1Ga0.8Mg0.2O3-δ solid electrolyte2018 - REIS, S.L.; MUCCILLO, E.N.S.The effects of small amounts of gallium oxide on intragrain and intergrain conductivity of La0.9Sr0.1Ga0.8Mg0.2O3-δ are investigated by impedance spectroscopy in the 280–420 °C range. Bulk specimens with 0.5, 1.0 and 1.5 mol% gallium oxide are prepared by solid state reaction at 1350 °C. All specimens achieved relative density values higher than 95%. The additive promotes grain growth indicating solid solution formation. A small fraction of the additive remains at grain boundaries and increases the fraction of the gallium-rich, LaSrGa3O7, impurity phase. The intragrain conductivity of gallium oxide containing specimens is higher than that of the parent solid electrolyte. Similar effect is found for the intergrain conductivity, which is maximum for 1 mol% gallium oxide addition.Artigo IPEN-doc 23171 Improved ionic conductivity of zirconia-scandia with niobia addition2017 - GROSSO, ROBSON L.; REIS, S.L.; MUCCILLO, E.N.S.The ionic conductivity and the crystalline structure of ZrO2−10 mol% Sc2O3- x mol% Nb2O5 solid electrolytes were investigated for x=0.25, 0.5 and 1. Dense specimens with relative densities higher than 95% were prepared by solid state reaction and sintered at 1500 °C for 5 h. Full stabilization of the cubic structure at room temperature was obtained for compounds with x=0.5 and 1, whereas the cubic and rhombohedric structures coexist for x=0.25. The highest ionic conductivity in codoped system was found for specimen containing 0.5 mol % niobium pentoxide, with the same order of magnitude as that of the parent solid electrolyte (zirconia-10 mol % scandia) in the high temperature range (above 600 °C). Preliminary investigation on phase stability shows that the isothermal conductivity of the new solid electrolyte remained constant up to 100 h at 600 °C. Niobium pentoxide addition was found to improve the overall ionic conductivity of zirconia-scandia solid electrolyte.