In Situ TEM Study of Structural Changes in Na-β″-Alumina Using Electron Beam Irradiation

Real-time structural changes in Na-β″-alumina were observed in situ using transmission electron microscopy (TEM) with electron beam irradiation. Na-β″-alumina has been widely investigated as a solid electrolyte material for sodium–sulfur secondary batteries owing to its high ionic conductivity. This high conductivity is known to be due to the Na(+) ions on the loosely packed conduction planes of Na-β″-alumina. In the present study, we acquired real-time videos of the generation of spinel blocks caused by the conduction of Na(+) ions. In addition, by observing Na extraction during electron beam irradiation, we experimentally confirmed that spinel block generation originates from the Na(+) ion conduction, which has been a subject of recent debate.