Strategy to improve phase compatibility between proton conductive BaZr0.8Y0.2O3-δ and nickel oxide

BaZr0.8Y0.2O3-delta (BZY20) is a promising candidate as an electrolyte in protonic ceramic fuel cells (PCFCs), and nickel (Ni) is known to show good electrode properties for the anode reaction. However, their compatibility seems to be questionable, since during the co-sintering process for cell fabrication, a second phase of BaY2NiO5 formed due to a reaction between BZY20 and NiO. The results in this work revealed that BaY2NiO5 was unstable against high temperature (1500 and 1600 degrees C), and could also be reduced in a hydrogen atmosphere at 600 degrees C. The products of these reactions may affect fuel cell performance. A systematic work was then performed to provide fundamental insight into the reactivity between BZY20 and NiO, which was found to be impacted significantly by the compositional homogeneity of the BZY20 powder used for cell fabrication, and also the BaO activity during the co-sintering process. It is concluded that improving the compositional homogeneity of BZY20, by elevating the final heating temperature for BZY20 from 1300 to 1600 degrees C in this work, and choosing a proper sintering strategy may improve effectively the phase purity of the cell.