Defect Equilibrium and Ambient Effects on Proton Conduction in Chemical Substitution-Free Hexagonal Perovskite Oxide Ba2ScAlO5 for Intermediate Temperature Energy Devices

This work presents a comprehensive investigation of Ba 2 ScAlO 5 , a hexagonal perovskite-related oxide possessing intrinsic oxygen vacancies without chemical substitution. This material exhibits a high concentration of surface-adsorbed oxygen as indicated by XPS analysis, while O 2 -TPD confirms its significant intrinsic oxygen vacancy content. H 2 O-TPD confirms synergistic physisorbed water and chemisorbed OH - , enhancing Intermediate temperature proton transport. Based on the defect equilibrium model, the influence of oxygen partial pressure and water vapor pressure on the conductive behavior was systematically studied under different atmospheres and temperatures. The results demonstrate that the conduction mechanism transitions from mixed ionic-hole in dry air to proton-dominated transport under humidified conditions within 500-700 °C. Therefore, Ba 2 ScAlO 5 is a promising, undoped electrolyte candidate for intermediate-temperature proton-conducting ceramic devices.