Evidence for interface-rate limited densification kinetics at Al₂O₃-GdAlO₃ interfaces characterized by in situ ultrahigh temperature transmission electron microscopy

The sintering behavior of single Al₂O₃ particles resting on GdAlO₃ is characterized using in situ transmission electron microscopy imaging. In bicrystal experiments, particles with lower Al₂O₃-GdAlO₃ phase boundary energies shrink via Ostwald ripening with no evidence of densification that would result from an atomic flux along the interface. Particles with higher Al₂O₃-GdAlO₃ phase boundary energies undergo intermittent rigid body motion associated with an interfacial flux mediated by interfacial line defects, e.g. disconnections. Long incubation periods elapse between these comparatively rapid rigid body motion events. The interfacial diffusivity during each event agrees with the magnitude of interfacial diffusion obtained from independent measurements of interfacial diffusivity. The results from the model experiments suggest that capillarity driven interfacial strain mediation, e.g. densification during sintering, is interface rate limited at the driving forces investigated.