Dislocation-point defect interaction on plasticity across the length scale in SrTiO3

TL;DR

This study investigates how Nb doping affects dislocation behavior and plasticity in SrTiO3 across nano, meso, and macro scales, revealing suppressed dislocation activity and increased yield stress.

Contribution

It provides a comprehensive multiscale analysis showing that Nb doping inhibits dislocation nucleation, multiplication, and mobility in SrTiO3, linking defect chemistry to mechanical properties.

Findings

Nb doping increases pop-in stresses and lattice friction.

Doped samples show ~50% higher yield stress.

Oxygen vacancies promote plasticity, Sr vacancies hinder dislocation motion.

Abstract

Point defect engineering is widely used to tailor the electronic and transport properties of complex oxides, yet its influence on dislocation plasticity remains poorly understood. Here, we establish how donor (Nb) doping modifies dislocation nucleation, multiplication, and mobility in single-crystal SrTiO3 by bridging nano-, meso-, and macroscale deformation. Using a combinatorial approach involving nanoindentation, cyclic Brinell indentation, and bulk uniaxial compression, we show that 0.5 wt% Nb doping consistently suppresses room-temperature plasticity. Nanoindentation reveals increased pop-in stresses, increased lattice friction stress, and reduced creep rates, indicating inhibited dislocation nucleation and motion with Nb doping. Mesoscale Brinell indentation exhibits discrete, widely spaced slip traces reflecting more difficult dislocation multiplication. Bulk uniaxial compression confirms ~50% higher yield stress in Nb-doped (0.5 wt%) SrTiO3 samples. Comparison with Fe-doped SrTiO3 (equivalent doping concentration) isolates the role of defect chemistry: oxygen vacancies promote incipient plasticity, whereas Sr vacancies dominate in Nb-doped SrTiO3, strongly hindering dislocation motion. This length-scale bridging approach consistently reveals suppressed dislocation nucleation, multiplication, and motion in the 0.5 wt% Nb-doped samples. These insights underline the importance of dislocation-defect chemistry on the mechanical behavior of functional oxides.