Strain phase equilibria and phase‐field method of ferroelectric polydomain: A case study of monoclinic K _x Na _{1 −  x} NbO ₃ thin films

Journal Article · Wed Aug 21 00:00:00 UTC 2024 · Journal of the American Ceramic Society

DOI: https://doi.org/10.1111/jace.20072 · OSTI ID:2434085

Wang, Bo ^[1]; Zhou, Meng‐Jun ^[2]; Ladera, Adriana ^[3]; Chen, Long‐Qing  ^[4]

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1. Materials Research Institute and Department of Materials Science and Engineering The Pennsylvania State University University Park Pennsylvania USA, Materials Science Division Lawrence Livermore National Laboratory Livermore California USA
2. State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Center of Smart Materials and Devices, School of Materials Science and Engineering Wuhan University of Technology Wuhan PR China
3. Department of Computer Science and Engineering University of South Florida Tampa Florida USA
4. Materials Research Institute and Department of Materials Science and Engineering The Pennsylvania State University University Park Pennsylvania USA

Abstract Knowledge of the thermodynamic equilibria and domain structures of ferroelectrics is critical to establishing their structure–property relationships that underpin their applications from piezoelectric devices to nonlinear optics. Here, we establish the strain condition for strain phase separation and polydomain formation and analytically predict the corresponding domain volume fractions and wall orientations of, relatively low symmetry and theoretically more challenging, monoclinic ferroelectric thin films by integrating thermodynamics of ferroelectrics, strain phase equilibria theory, microelasticity, and phase‐field method. Using monoclinic K _x Na _{1 −  x} NbO ₃ (0.5 <  x  < 1.0) thin films as a model system, we establish the polydomain strain–strain phase diagrams, from which we identify two types of monoclinic polydomain structures. The analytically predicted strain conditions of formation, domain volume fractions, and domain wall orientations for the two polydomain structures are consistent with phase‐field simulations and in good agreement with experimental results in the literature. The present study demonstrates a general, powerful analytical theoretical framework to predict the strain phase equilibria and domain wall orientations of polydomain structures applicable to both high‐ and low‐symmetry ferroelectrics and provide fundamental insights into the equilibrium domain structures of ferroelectric K _x Na _{1 −  x} NbO ₃ thin films that are of technology relevance for lead‐free dielectric and piezoelectric applications.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE; USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC52-07NA27344
• OSTI ID: 2434085
• Report Number(s): LLNL--JRNL-862607
• Journal Information: Journal of the American Ceramic Society, Journal Name: Journal of the American Ceramic Society Journal Issue: 12 Vol. 107; ISSN 0002-7820
• Publisher: Wiley-BlackwellCopyright Statement
• Country of Publication: United States
• Language: English