Electrical properties and transport numbers of yttrium and gadolinium co-doped BaCe0.5Zr0.3Y0.2-xGdxO3-δ proton-conducting electrolyte

BaCe0.5Zr0.3Y0.2-xGdxO3-delta (x = 0, 0.05, 0.1) proton-conducting electrolyte materials co-doped with Y (yttrium) and Gd (gadolinium) were successfully synthesized by solid-state reaction method. The influence of Gd concentration on the phase composition, chemical stability, and electrical conductivity of BaCe0.5Zr0.3Y0.2-xGdxO3-delta (BCZYGx, x = 0, 5, and 10) materials were systematically investigated under different atmospheres within the temperature range of 500-800 degrees C. The BCZYG5 material presents enhanced chemical stability and conductivity in comparison to the pristine BZCY. Electrochemical impedance spectra analysis using the distribution of relaxation times (DRT) and equivalent circuit scheme (ECS) methods revealed that BCZYG5 demonstrates a maximum electrical conductivity of 8.90 x 10-3 S cm-1 at 800 degrees C under 20% O2 and 4.51 kPa H2O. The defect equilibrium model was employed to calculate the partial conductivity and transport numbers. The results indicate a decrease in proton transport numbers with rising temperature, while oxygen ion and electron-hole transport numbers increase. The doping of Gd inhibits electron conduction in both the BCZYG5 and BCZYG10, as illustrated by the map of the dominant region of each carrier. This study will serve as a reference for future research.