Characterization of high Zr/Ce ratio Ba(Zr, Ce, Y)O3-δ proton conductors: investigating the impact of Y on materials properties

Abstract

Acceptor substituted Ba(Zr,Ce)O3 proton conducting oxides have attracted significant attention due to their excellent proton conductivity at intermediate temperatures (400-600 °C). A high Zr/Ce ratio is crucial for maintaining stability in humid or other harsh atmospheres. Herein, a systematic study was conducted on the phase composition, microstructure, and the resulting hydration ability and electrochemical performance of high Zr/Ce ratio Ba(Zr,Ce)O3 solid solutions with different Y substitution levels (10 at.% to 30 at.%). In this substitution range no apparent secondary phase can be found from XRD, leading to a continuous increase in hydration content. Y-rich phase was observed in SEM in highly Y substitutional composition. The impact of Y on proton conduction was examined using EIS and given special attention, elucidating the effects of varying amounts of Y on bulk proton conduction. The increase of proton conductivity primarily due to the increased charge carrier (proton) concentration caused by Y substitution. Different concentrations of Y have little effect on proton mobility, indicating a compromise between different mechanisms such as the Y trapping effect and the nano-percolation effect. The grain boundary proton conduction was discussed combining the TEM-EDS results to explain the space charge layer effect. Mechanical properties and thermo-chemical stability were also considered to pave the way for real applications.