Probing oxygen ion transport in solid state oxides: A technical review

The study of ion transport in solid state ionic materials underpins the fast development of many electrochemical technologies such as solid state batteries, solid oxide cells, proton conducting solid oxide fuel cells. In order to obtain the ion transport dynamics, different in situ and ex situ techniques have been developed to probe ion transport while each method has its inherent merits and weaknesses. The choice of the method for measuring ionic mass transport primarily depends upon the appropriacy and accessibility of the technique based on sample properties, targeted information of interest and technical limitations. This review introduces aspects of the underlying principles, discusses and compares different techniques available to date in the literature to obtain oxygen mass transport kinetics, primarily focussing on experimental techniques, in particular the isotope exchange depth profiling and electrical conductivity relaxation methods, together with a brief introduction on computational tools.