Discovery of Electrochemically Induced Grain Boundary Transitions

TL;DR

This study reveals how electric currents can induce grain boundary transitions in materials, significantly affecting microstructure evolution and offering new ways to tailor material properties electrochemically.

Contribution

It uncovers the mechanism of electrochemically induced grain boundary transitions using a combination of advanced microscopy, spectroscopy, and computational modeling.

Findings

Electrochemical reduction causes grain boundary disorder-to-order transitions.

Such transitions increase grain boundary diffusivities and mobilities.

This leads to abnormal grain growth and microstructural changes.

Abstract

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.