Effect of Two Different ZnO Addition Strategies on the Sinterability and Conductivity of the BaZr0.4Ce0.4Y0.2O3−δ Proton-Conducting Ceramic Electrolyte

A comparative study has been made to relate the effect of different addition strategies for the sintering aid of ZnO (∼1 wt %) on the performance of the BaZr0.4Ce0.4Y0.2O3−δ (BZCY442) electrolyte in order to improve the sinterability and conductivity of this material more efficiently. Two samples, Zn-doped BaCe0.4Zr0.4Y0.15Zn0.05O3−δ (BZCYZn, internal doping) and BZCY–ZnO (BZCY442 mixed with ZnO, external addition), were synthesized. The BZCYZn crystallized at a single phase after sintering at 1350 °C, and the segregation of Y2O3 was observed in BZCY–ZnO in the same conditions. The relative densities of the BZCYZn and BZCY–ZnO samples sintered at 1350 °C for 5 h were 98 and 94%, respectively. The high total conductivity in BZCYZn benefited from the low barrier height at the grain boundary core determined by the Mott–Schottky space charge layer model, which was 0.15 V for BZCYZn and 0.26 V for BZCY–ZnO. A cell with BZCYZn as the electrolyte generated a power density of 414.5 mW cm–2 at 700 °C. The total ionic transport number of BZCYZn was determined to be ∼0.90 at 600 °C under fuel cell conditions.