Electrical and Hydrogen Reduction Enhances Kinetics in Doped Zirconia and Ceria: II. Mapping Electrode Polarization and Vacancy Condensation in YSZ

TL;DR

This study investigates how electrical and hydrogen reduction processes improve the reaction kinetics in doped zirconia and ceria, revealing how electrode polarization and vacancy condensation influence microstructure and oxygen potential distribution.

Contribution

It introduces a microstructural mapping method linking grain size to local oxygen potential, highlighting the role of electrode kinetics and vacancy behavior in ceramic microstructure.

Findings

Abrupt oxygen potential transitions under high current density

Oxygen vacancy condensation causes cavitation in reducing environments

Electrode kinetics directly affect ceramic microstructure and properties

Abstract

Knowing the correlation between grain boundary mobility and oxygen potential in yttria stabilized zirconia (YSZ), we have utilized the grain size as a microstructural marker to map local oxygen potential. Abrupt oxygen potential transition is established under a large current density and in thicker samples. Cathodically depressed oxygen potential can be easily triggered by poor electrode kinetics or in an oxygen-lean environment. Widespread cavitation in the presence of highly reducing oxygen potential suggests oxygen vacancy condensation instead of oxygen bubble formation as commonly assumed for solid oxide fuel/electrolysis cells. These results also suggest electrode kinetics has a direct influence on the microstructure and properties of ceramics sintered under a large electric current.