  Electric fields and currents, which are used in innovative materials
processing and electrochemical energy conversion, can often alter
microstructures in unexpected ways. However, little is known about the
underlying mechanisms. Using ZnO-Bi2O3 as a model system, this study uncovers
how an applied electric current can change the microstructural evolution
through an electrochemically induced grain boundary (GB) transition. By
combining aberration-corrected electron microscopy, photoluminescence
spectroscopy, first-principles calculations, a generalizable thermodynamic
model, and ab initio molecular dynamics, this study reveals that
electrochemical reduction can cause a GB disorder-to-order transition to
markedly increase GB diffusivities and mobilities. Consequently, abruptly
enhanced or abnormal grain growth takes place. These findings advance our
fundamental knowledge of GB complexion (phase-like) transitions and electric
field effects on microstructural stability and evolution, with broad scientific
and technological impacts. A new method to tailor the GB structures and
properties, as well as the microstructures, electrochemically can also be
envisioned.
