Jie Wang's blog
The influence of crack face electrical boundary conditions on the nonlinear behavior of ferroelectric single crystalSubmitted by Jie Wang on Thu, 2013-05-02 08:37.
doi:10.1088/0964-1726/22/6/065001 (FEATURED ARTICLE of IOP)
Effect of electrical boundary conditions on the polarization distribution around a crack in a ferroelectric single domainSubmitted by Jie Wang on Sun, 2011-01-02 09:41.
Polarization distributions around an open crack with different electrical boundary conditions in a single crystal ferroelectric are investigated by using a phase field model. The surface effect of polarization is taken into account in the phase field model, which has not been included in previous ferroelectric crack models. The simulation results show that the impermeable crack and the crack filled with air have a significant influence on the polarization distribution, while the permeable and the crack filled with water have little influence. It is also found that the zero boundary condition of polarization increases the influence of the crack on the permeable crack and the crack filled with water.
The ability to control the domain patterns in ferroelectric nanostructures holds promise as a method to tailor physical properties for specific applications. We proposed a new way to control the domain patterns in ferroelectric nanostructures. Desirable domain patterns can be obtained through different surface charges. The surface charges can be supplied by the atomic and molecular adsorbates on the surfaces of ferroelectric nanostructures.
Ferroelectric nanotubes have potential application in inkjet printing and drug delivery due to their piezoelectric property and unique geometry. For different applications, different electrical boundary conditions are applied to ferroelectric nanotubes. In the present work, domain structures in ferroelectric nanotubes (FNTs) under different electrical boundary conditions are predicted through a phase field model. Simulation results show that domain structures are highly dependent on the compensation of polarization-induced surface charges.
Influence of depolarization field on polarization states in epitaxial ferroelectric thin films with biaxial misfit strainsSubmitted by Jie Wang on Fri, 2007-05-25 07:23.
Depolarization field and misfit strain are two important factors that may greatly influence the properties of ferroelectric thin films. The effect of depolarization field on polarization states of single-domain ferroelectric thin films with nonequally biaxial in-plane misfit strains are studied in the present work by numerically solving three coupled Euler-Lagrange equations, which are derived from the minimization of total free energy.
Polarization switching-induced shielding or anti-shielding of an electrically permeable crack in a mono-domain ferroelectric material with the original polarization direction perpendicular to the crack is simulated by a phase field model based on the time-dependent Ginzburg-Landau equation. The domain wall energy and the long-range mechanical and electrical interactions between polarizations are taken into account. The phase field simulations exhibit a wing-shape- switched zone backwards the crack tip. The polarization switching-induced internal stresses shield the crack tip from applied mechanical loads.
The Eighth International Conference on Fundamentals of Fracture (ICFF VIII) is the successor of the previous seven held at NBS, Gaithersburg (USA, 1983), Gatlinburg (USA, 1985), Irsee (Germany, 1989), Urabandai (Japan, 1993), NIST, Gaithersburg (USA, 1997), Cirencester (UK, 2001), and Nancy (France, 2005). You are warmly invited to participate in ICFF VIII which will be held 3-7 January 2008 in Hong Kong University of Science and Technology, Hong Kong, and in Guangzhou, China. As the previous conferences, ICFF VIII provides an international forum for presentation and discussion of the latest scientific and technological development in fundamentals of fracture. The general theme of ICFF VIII is to cover all aspects of fracture at a fundamental level, including contributions from those working in the disciplines of Continuum Mechanics, Physics, Chemistry, Bioscience, Metallurgy, Ceramics, Polymer Science, etc. You are cordially invited to submit an abstract to join in this memorable event.
Time-dependent Ginzburg-Laudau (TDGL) equation is the simplest kinetic equation for the temporal evolution of a continuum field, which assumes that the rate of evolution of the field is linearly proportional to the thermodynamical driving force. The computation model based on this equation is also called phase field model. Phase field simulation can predict quite beautiful patterns of microstructures of material. It has been widely applied to simulating the evolution of microstructure by choosing different field variables. For example, using the single conserved field (concentration field), continuum phase field models has been employed to describe the pattern formation in phase-separating alloys (Nishimori and Onuki, 1990 Phys. Rev. B, 42,980) and the nanoscale pattern formation of an epitaxial monolayer (Lu and Suo, 2001 J. Mech. Phys. Solids, 49,1937). On the other hand, using the nonconserved field (polarization field), the phase field model has been utilized to simulating the formation of domain structure in ferroelectrics (Li et al. 2002 Acta Mater, 50,395). The thermodynamical driving force is usually nonlinear with respect to the field variable. In the case of nonlinearity, the solution to TDGL equation may not be unique. Different grid density, length of iteration step, initial state and random term (introduced to describe the nucleation process) may induce different results in the simulation. Does anyone investigate the effect of these factors on the final pattern? I wonder whether we can prove the solution is unique or not.
The effect of long-range elastic interactions on the toroidal moment of polarization in a ferroelectric nanoparticleSubmitted by Jie Wang on Thu, 2006-11-02 02:23.
The effect of long-range (LR) elastic interactions on the toroidal moment of polarization in a two-dimensional ferroelectric particle is investigated using a phase field model. The phase field simulations exhibit vortex patterns with purely toroidal moments of polarization and negligible macroscopic polarization when the spontaneous strains are low and the simulated ferroelectric size is small. However, a monodomain structure with a zero toroidal moment of polarization is formed when the spontaneous strains are high in small simulated ferroelectrics, indicating that, because of the LR elastic interactions, high values of spontaneous strains hinder the formation of polarization vortices in ferroelectric particles. Applied Physics Letters 88, 182904 (2006)