Frequency Dependence of Cationic Interdiffusion Kinetics in Er ₂ O ₃ /Y ₂ O ₃ Diffusion Couples Under AC Flash Events

ABSTRACT The cationic interdiffusion behavior during flash events was investigated using Er 2 O 3 /Y 2 O 3 diffusion couples under alternating current (AC) electric fields at different frequencies (50–2000 Hz) with similar specimen temperatures. The diffusion length of Er 3+ in the Y 2 O 3 body was athermally enhanced with increasing frequency. The diffusion distance reached 20 µm after holding at 50 Hz for 3 h. However, a 10 µm longer diffusion distance was observed in the specimen treated at 2000 Hz for the same duration despite similar specimen temperatures. Notably, at a frequency of 2000 Hz, pronounced grain boundary migration occurred in conjunction with the spread of Er 3+ cations into the Y 2 O 3 grains, resulting in a layer‐by‐layer modulation of the Er concentration. Based on these results, we propose a mechanism for cationic mass transport into grain interiors during AC‐flash events. The proposed mechanism is driven by a synergistic interaction between grain boundary migration amplified at higher frequencies, and grain boundary diffusion. Grain boundary migration was possibly affected by the variations in the pore structures formed at different frequencies, which could result in frequency‐dependent mass transport behaviors.