Strain-driven phase transitions and associated dielectric/piezoelectric anomalies in BiFeO3 thin films
ABSTRACT Strain-driven phase transitions and related intrinsic polarization, dielectric, and piezoelectric properties for single-domain films were studied for BiFeO 3 using phenomenological Landau–Devonshire theory. A stable and mixed structure between tetragonal and rhombohedral-like (monoclinic) phases is predicted at a compressive misfit strain of um=-0.0382 without an energy barrier. For a tensile misfit strain of um=0.0272 , another phase transition between the monoclinic and orthorhombic phases was predicted with sharply high dielectric and piezoelectric responses.
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ABSTRACT: Dielectric response of the BiFeO3 films in a parallel-plate capacitor configuration is studied in the frequency range 1 MHz–30 GHz and under dc electric field up to 45 V/μm in view of their application in tunable film bulk acoustic wave resonators. The observed relatively high permittivity 130 without remarkable frequency dispersion is explained by contribution of the domain wall vibrations. It is shown that the substrate induced strain and Maxwell-Wagner contributions are negligible. The measured dielectric response allows estimation of the BiFeO3 sound velocity and acoustic impedance as 3100 m/s and 26 · 10 kg/ms, respectively.Integrated Ferroelectrics 01/2012; 134(1):111-117. · 0.38 Impact Factor