Dynamics of anisotropic oxygen-ion migration in strained cobaltites

TL;DR

This study reveals how strain influences anisotropic oxygen-ion migration pathways in ultrathin cobaltites, providing insights for engineering oxygen vacancy channels to optimize ionic conduction in electronic devices.

Contribution

It demonstrates strain-dependent oxygen vacancy channel switching mechanisms and constructs atomic-scale migration pathways in cobaltites, advancing understanding of ion transport control.

Findings

Vertical-to-horizontal OVC switching under tensile strain

Horizontal-to-diagonal switching under compression

Strain-dependent phase diagram of OVC stability

Abstract

Orientation control of oxygen vacancy channel (OVC) is a highly desirable for tailoring oxygen diffusion as it serves fast transport channel in ion conductors, which is widespread exploited in solid-state fuel cells, catalysts, and ion-batteries. Direct observation of oxygen-ions hopping towards preferential vacant sites is a key to clarifying migration pathways. Here we report the anisotropic oxygen-ion migration mediated by strain in ultrathin cobaltites via in-situ thermal activation in an atomic-resolved transmission electron microscopy. Oxygen migration pathways are constructed on the basis of the atomic structure during the OVC switching, which is manifested as the vertical-to-horizontal OVC switching under tensile strain, but the horizontal-to-diagonal switching under compression. We evaluate the topotactic structural changes to OVC, determine the crucial role of tolerance factor for OVC stability and establish the strain-dependent phase diagram. Our work provides a practical guide for engineering OVC orientation that is applicable ionic-oxide electronics.