Y-Gd-Zn tri-doped BaCeO3-BaZrO3 proton conducting electrolytes with improved electrical and transport properties

In this study, the BaCeO₃-BaZrO₃ material was modified using an internal addition method of ZnO as a sintering aid. resulting in the synthesis of the Zn, Y and Gd triple-doped BaCe_0.6Zr_0.2-xY_0.15Gd_0.05Zn_xO_3-δ (BCZYGZnx, x = 0, 0.02, 0.04, 0.06) materials. The impact of Zn doping as a sintering aid on the phase structure, microscopic morphology, electrical and transport properties of BCZYGZnx proton conductor materials were systematically investigated. The XRD results demonstrate that BCZYGZnx materials with a single perovskite structure have been successfully synthesized by the solid-phase reaction method. The SEM analysis results demonstrate that the introduction of Zn²⁺ can markedly enhance the sintering performance of the materials. A comprehensive analysis of relaxation time distribution (DRT) and equivalent circuit scheme (ECS) was conducted to investigate the effects of temperature, test atmosphere and Zn doping concentration on the conductivity of BCZYGZnx materials. The results demonstrate that BCZYGZn0.04 material exhibits the highest conductivity of 9.25 × 10^–3 S cm⁻¹ at 700 °C under pH₂O = 0.018 atm and pO₂ = 0.20 atm atmospheres. The proton transference number of the BCZYGZnx materials were calculated according to the defect equilibrium model and the results indicate that BCZYGZn0.04 material has a higher proton transference number, reaching 0.88 at 600 °C. Furthermore, the proton transference properties of the material are mainly affected by the water pressure and less by the oxygen partial pressure according to the predominant regions of proton conduction in diverse atmospheres. In conclusion, the Zn doping strategy enhances the electrical and transport properties of BaCeO₃-BaZrO₃ materials.