The dependence of cationic diffusivity on current density was investigated using Er 2 O 3 /Y 2 O 3 diffusion couples subjected to alternating current (AC) flash events with current density amplitudes of 30–60 mA∙mm −2 and furnace temperatures of 1050–1300°C at a constant frequency of 1000 Hz. An increase in current density athermally enhanced both the grain boundary and lattice diffusivities, reducing activation energies, whereas the effect of Joule heating on specimen temperature was relatively limited. Porosity also considerably increased with current density, especially at grain boundaries, suggesting that grain boundaries could serve as the source of oxygen gas bubbles (pores) and vacancies under AC flash events. The strong correlation between diffusivity enhancement and porosity evolution indicates that oxygen vacancies generated along grain boundaries play a main role in promoting cationic diffusion during AC flash events.
Yang et al. (Mon,) studied this question.