ICAMS / Interdisciplinary Centre for Advanced Materials Simulation

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Theoretical and experimental study of the core structure and mobility of dislocations and their influence on the ferroelectric polarization in perovskite KNbO3

P. Hirel, A. F. Mark, M. Castillo-Rodriguez, W. Sigle, M. Mrovec, C. Elsässer.

Physical Review B, 92, 214101, (2015)

Abstract
Potassium niobate KNbO3 is a lead-free perovskite and a promising candidate to replace lead-containing ferroelectrics related to PbTiO3. In this study, we use atomistic computer simulation and transmission electron microscopy to investigate dislocations in KNbO3, first to establish the relationship between their atomic-scale properties and the macroscopic mechanical behavior, and second to study their influence on the ferroelectric properties of the material. The easiest dislocation glide system is found to be <110> {(1) over bar 10} at all temperatures, independent from structural phase transformations. The mobility of dislocations and the evolution of the microstructure are measured from room temperature up to 1173 K. A sharp transition in the yield stress is found around 800 K, attributed to the additional activation of the <100> {010} glide system at high temperature. Atomistic simulations quantify the effect of dislocations on the ferroelectric polarization, and TEM observations give indication of the nucleation of domain walls at dislocation cores.


DOI: 10.1103/PhysRevB.92.214101
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