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The proton conductor oxide yttrium doped barium zirconate (BaZr1-xYxO3-δ, BZYx) is a promising solid electrolyte for solid oxide fuel cells (SOFC) operating at intermediate temperatures (400 to 700 o C). However, the BZY refractory nature (MP ~ 2600 o C) inhibits the achievement of the densification needed for application in SOFCs (relative density ≥ 95% T.D.), requiring long dwell times and high temperatures (T ≥ 1600 o C, t ≥ 24 h). Those extreme conditions cause barium stoichiometry deviation, which affects the defect chemistry and the depletion of proton conductivity. Therefore, BZY processing in less aggressive conditions, preserving cation stoichiometry, leading to dense microstructures with low intergranular resistivity are the great challenges of the scientific community nowadays. Aiming to increase particles sinterability, BZYx (x = 10 to 50 mol% of Y 3+ ), solid solutions where synthesized by the Oxidant Peroxide Method (OPM). The original OPM experimental procedure was modified to allow the BZY formation with different dopant content. One of the modifications was to carry out the synthesis under laboratory and nitrogen atmospheres. The study of structural, thermal, morphological, thermochemical and electrical properties of all samples was performed. The samples where calcined at different temperatures and the particles sinterability and densification were also investigated. The thermochemical properties of BZYx solid solutions were investigated by high temperature oxide melt solution calorimetry, for evaluation of the formation enthalpies (ΔHf,ox). The total electrical conductivity of the BZY10 and BZY20 sintered samples synthesized under nitrogen was 1.6 x 10 -3 and 1.3 x 10 -3 S/cm at 530 o C, respectively. The blocking of charge carriers at interfaces contributes to the low total electrical conductivity. Raman spectroscopy analysis and the evaluated ΔHf,ox values obtained suggest that from 20 mol% Y 3+ , defect interaction might happen, leading to vacancy clustering. This effect might cause the depletion of mobile oxygen vacancies, affecting the mobility of protons, with a decrease in proton conductivity.

Caracterização de zirconato de bário dopado com ítrio, sintetizado pelo método dos peróxidos oxidantes