Phase-field simulation of domain size effect on dielectric and piezoelectric responses in K_0.5Na_0.5NbO₃ epitaxial thin films with superdomain structures

Journal Article · Mon Feb 13 00:00:00 UTC 2023 · Acta Materialia

DOI:https://doi.org/10.1016/j.actamat.2023.118777· OSTI ID:1959681

Zhou, Meng-Jun ^[1]; Wang, Bo ^[2]; Peng, Kun ^[1]; Liu, Han-Xing ^[1]; Chen, Long-Qing ^[3]; Nan, Ce-Wen ^[4]

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1. Wuhan Univ. of Technology (China)
2. Pennsylvania State Univ., University Park, PA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
3. Pennsylvania State Univ., University Park, PA (United States)
4. Tsinghua Univ., Beijing (China)

Size effects of mesoscale ferroelectric domains on the macroscopic dielectric and piezoelectric responses in domain-engineered bulk piezocrystals have been extensively studied for more than two decades. However, less is known about the domain size effects in ferroelectric epitaxial thin films, especially for films consisting of low-symmetry ferroelectric phases and exhibits hierarchical superdomain structures. Herein, using phase-field simulations, we systemically evaluate the effective out-of-plane dielectric and piezoelectric coefficients, κ$$^{*}_{33}$$ and d$$^{*}_{33}$$, as a function of the domain periods for two types of superdomain structures in ferroelectric K_0.5Na_0.5NbO₃ epitaxial thin films. In one type of the superdomain structures, we find that more than 70% increase of κ$$^{*}_{33}$$ and nearly 20% increase of d$$^{*}_{33}$$ can be achieved by tuning the domain period by a few tens of nanometers. Dissimilar behaviors are found when the domain period varies along different lateral directions, suggesting anisotropic domain size effects in thin films. By analyzing the local dielectric and piezoelectric responses from each domain variants and domain walls, we reveal that the domain size effect is governed by the variation of out-of-plane polarization inside the domains. Moreover, we also demonstrate enhanced domain size effects by modulating the misfit strains and temperature to approach the polymorphic phase boundaries, suggesting tunability of the size effect by doping and strain engineering. Furthermore, our results reveal multimodal domain size dependence of dielectric and piezoelectric responses in low-symmetry ferroelectric epitaxial thin films, implying that domain size engineering can be used to tune macroscopic properties of thin-film ferroelectrics, similar to their bulk counterparts.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: National Science Foundation (NSF); USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC52-07NA27344
• OSTI ID: 1959681
• Report Number(s): LLNL-JRNL-842352; 1064608
• Journal Information: Acta Materialia, Journal Name: Acta Materialia Vol. 248; ISSN 1359-6454
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
42 ENGINEERING
Ferroelectric thin film
K0.5Na0.5NbO3
dielectric properties
domain structure
phase-field simulation
piezoelectric properties