Exploring the Conductivity Landscape of Notable Ceramic Electrolytes Under Varying Ambient Conditions

Ceramic electrolytes play a crucial role in the development of ceramic electrochemical cells. In this study, we explore the conductivity behavior of two notable ceramic electrolytes, oxide ion conducting Ce0.8Sm0.2O2 (SDC) and proton conducting BaCe0.7Zr0.1Y0.1Yb0.1O3-δ (BCZYYb), under varying ambient conditions. Using the DC four-probe method, we examined the conductivity of these electrolytes in the temperature range of 850–450 °C under pure air, 3% H2O-air, and 5% H2O-air conditions. The results reveal that SDC has a higher total conductivity, mainly oxide ions, and electrons, than BCZYYb, which conducts protons more effectively. SDC has a higher electron density and larger crystallite size than BCZYYb, which could account for its higher bulk conductivity. BCZYYb exhibits effective proton conductivity at lower temperatures (below 750 °C) through hydration with lower activation energies. The enthalpy of protonation in BCZYYb reaches −21.38 kJ mol−1 under 3% H2O-air conditions from 450 to 550 °C. The findings of this study provide critical insights into the fundamental mechanisms that govern the conductivity of ceramic electrolytes and can guide future efforts to optimize ceramic electrolytes for advanced electrochemical conversion and energy storage applications.