Evidence for enormous iodide anion migration in lanthanum oxyiodide-based solid.

The I ion conduction was demonstrated and quantified in the LaSrZnOI solid. The I ion is considered to be an inferior conductor because of its large ionic size compared to the previously reported conducting ion species. Using modified Tubandt electrolysis, a weight increase at the anodic pellet and a corresponding weight decrease at the cathodic pellet were observed. The weight changes were in good agreement with the theoretical values estimated by considering pure I ion migration. Furthermore, the iodine element appeared at the anode, and the iodine concentration at the cathode decreased after electrolysis, indicating that the migrating species was only I. This is the first study to elucidate the conduction of iodide ions in solids.