Oxygen Vacancies at Dislocation Core Modulate Plasticity in Strontium Titanate

TL;DR

This study combines advanced microscopy, spectroscopy, and simulations to reveal how oxygen vacancies at dislocation cores influence plasticity in SrTiO3, highlighting vacancy evolution as a key factor in dislocation mobility.

Contribution

It provides the first direct observation and correlation of dislocation core structure, oxygen vacancy density, and mobility during deformation in an oxide material.

Findings

Short dislocation loops are Ti-reduced and oxygen-deficient at the core.

Longer loops remain near stoichiometry in the core.

Oxygen-vacancy trails modulate dislocation glide in SrTiO3.

Abstract

Dislocation core chemistry in oxides critically influences mechanical behavior and functionality; yet the evolution of core chemistry during the dislocation motion in them has not been directly observed. Here, using SrTiO3 as a model material, we combine aberration-corrected scanning transmission electron microscopy and electron energy-loss spectroscopy with atomic-level molecular dynamics (MD) simulations to correlate the <110>{1-10} dislocation core structure, oxygen vacancy density, charge state, and mobility with each other. We find that the mechanically induced dislocation loops exhibit dissociated cores, whose oxygen vacancy density depends on the gliding distance: short loops are Ti-reduced and oxygen-deficient at the edge dislocation core, whereas longer loops remain close to stoichiometry in both the edge and screw components. MD simulations reveal that kink-assisted edge dislocation glide in SrTiO3 leaves oxygen-deficient trails behind, modulating the oxygen content inside the edge core. These results demonstrate that oxygen-vacancy evolution at the dislocation core intrinsically couples with plasticity in ionic crystals, suggesting a mechanism for oxygen vacancy-dependent dislocation mobility in plastically deformed oxides.