Insights on the electrochemical behavior of BZY and BZCY proton conductors densified with a low percentage of Ni or Cu

Abstract

The reduction of operating temperatures of solid oxide electrochemical cells requires the development of novel materials, particularly those with high conductive charge carriers. This scenario presents challenges in developing proton conductive electrolytes and optimizing thermal treatments for their densification. A simple strategy for obtaining dense BaZr_0.8Y_0.2O_3-δ (BZY) and BaZr_0.7Ce_0.2Y_0.1O_3-δ (BZCY) ceramics, which represent the most frequently investigated proton conductive ceramics today, is presented in this paper and complies with using a low percentage of nickel or copper (1 wt.%), while minimizing their inclusion in the structure in order to minimize their possible electronic leakage in the electrolyte. Structural, morphological, and electrochemical analyses were carried out and results demonstrated a dependence of the overall conductivity on the type of perovskite and the nature of sintering aid, as well as the structural and morphological characteristics of BZY and BZCY. There is a noticeable difference between BZY and BZCY in terms of the propensity to achieve high densification, with the second more prone to do this. On the other hand, BZCY showed a particular tendency to promote electronic leakages, particularly at high temperatures due to the presence of Ce and exacerbated by reducing conditions. In spite of the 99.2% densification achieved with Cu-doped BZCY prepared according to one of the employed methods, the morphology must be improved further for the specimen to gain superior electrical properties.