Multiscale Simulations of Defect Dipole-Enhanced Electromechanical Coupling at Dilute Defect Concentrations

Abstract

The role of defects in solids of mixed ionic-covalent bonds such as ferroelectric oxides is complex. Current understanding of defects on ferroelectric properties at the single-defect level remains mostly at the empirical level, and the detailed atomistic mechanisms for many defect-mediated polarization-switching processes have not been convincingly revealed quantum mechanically. We simulate the polarization-electric field (P-E) and strain-electric field ({$\epsilon$}-E) hysteresis loops for BaTiO3 in the presence of generic defect dipoles with large-scale molecular dynamics and provide a detailed atomistic picture of the defect dipole-enhanced electromechanical coupling. We develop a general first-principles-based atomistic model, enabling a quantitative understanding of the relationship between macroscopic ferroelectric properties and dipolar impurities of different orientations, concentrations, and dipole moments. We find that the collective orientation of dipolar defects relative to the external field is the key microscopic structure feature that strongly affects materials hardening/softening and electromechanical coupling. We show that a small concentration (0.1 at.%) of defect dipoles dramatically improves electromechanical response. This offers the opportunity to improve the performance of inexpensive polycrystalline ferroelectric ceramics through defect dipole engineering for a range of applications including piezoelectric sensors, actuators, and transducers.

References in corpus (4)

• Charge migration in Pb(Zr,Ti)O3 ceramics and its relation to ageing, hardening and softening
• The nature of iron-oxygen vacancy defect centers in PbTiO3
• Formation and switching of defect dipoles in acceptor doped lead titanate: A kinetic model based on first-principles calculations
• High-frequency electron paramagnetic resonance investigation of the Fe3+ impurity center in polycrystalline PbTiO3 in its ferroelectric phase

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• Control of ferroelectric domain wall dynamics by point defects: Insights from ab initio based simulations
• Improving the Functional Control of Aged Ferroelectrics using Insights from Atomistic Modelling
• Point defect design in (Ba,Sr)TiO${}_3$ -- an insight on agglomeration