Investigation of alumina- and scandia-doped zirconia electrolyte for solid oxide fuel cell applications: Insights from broadband impedance spectroscopy and distribution of relaxation times analysis

Zirconia based oxygen conductors are state of the art solid electrolytes used for solid oxide fuel cell applications. In this study, we investigated zirconia double-doped with aluminium and scandium oxide. The Al0.04Sc0.06Zr0.9O1.95 electrolyte was prepared using Pechini method. In the 300–800 K temperature range, this material's structure is cubic with a fraction of monoclinic modification, while above 800 K it becomes completely cubic. The ceramic form of Al0.04Sc0.06Zr0.9O1.95 electrolyte was investigated using broadband impedance spectroscopy, utilizing equivalent circuit analysis and distribution of relaxation times (DRT) technique. The high-frequency relaxation process's complexity observed in the spectra's DRT representation at temperatures up to 500 K was associated with the two zirconia phases. The Al0.04Sc0.06Zr0.9O1.95 electrolyte was tested in a hydrogen-oxygen laboratory solid fuel cell in the temperature range 973–1123K. Understanding the fundamentals of the relaxation processes is necessary to increase the durability of the ceramic electrolyte in the fuel cell.