Browsing by Author "Wang, Junling"

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Strain-driven phase transitions and associated dielectric/piezoelectric anomalies in BiFeO(3) thin films
(2010-10-11)
Huang, C. W.
;
Chu, Y. H.
;
Chen, Z. H.
;
Wang, Junling
;
Sritharan, T.
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 u(m)=-0.0382 without an energy barrier. For a tensile misfit strain of u(m)=0.0272, another phase transition between the monoclinic and orthorhombic phases was predicted with sharply high dielectric and piezoelectric responses. (c) 2010 American Institute of Physics. [doi:10.1063/1.3499658]
Strain-driven phase transitions and associated dielectric/piezoelectric anomalies in BiFeO3 thin films
(2010-10-11)
Huang, C. W.
;
Chu, Y. H.
;
Chen, Z. H.
;
Wang, Junling
;
Sritharan, T.
Strain-driven phase transitions and related intrinsic polarization, dielectric, and piezoelectric properties for single-domain films were studied for BiFeO3 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 u(m)=-0.0382 without an energy barrier. For a tensile misfit strain of u(m)=0.0272, another phase transition between the monoclinic and orthorhombic phases was predicted with sharply high dielectric and piezoelectric responses. (c) 2010 American Institute of Physics. [doi:10.1063/1.3499658]
Universal Ferroelectric Switching Dynamics of Vinylidene Fluoride-trifluoroethylene Copolymer Films
(2014-04-24)
Hu, Wei Jin
;
Juo, Deng-Ming
;
You, Lu
;
Wang, Junling
;
Chen, Yi-Chun
In this work, switching dynamics of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer films are investigated over unprecedentedly wide ranges of temperature and electric field. Remarkably, domain switching of copolymer films obeys well the classical domain nucleation and growth model although the origin of ferroelectricity in organic ferroelectric materials inherently differs from the inorganic counterparts. A lower coercivity limit of 50 MV/m and 180 degrees domain wall energy of 60 mJ/m(2) are determined for P(VDF-TrFE) films. Furthermore, we discover in copolymer films an anomalous temperature-dependent crossover behavior between two power-law scaling regimes of frequency-dependent coercivity, which is attributed to the transition between flow and creep motions of domain walls. Our observations shed new light on the switching dynamics of semi-crystalline ferroelectric polymers, and such understandings are critical for realizing their reliable applications.