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Micromechanical simulation of ferroelectric domain processes at crack tips
摘要： The electromechanical loading situation at cracks in ferroelectric ceramics is essentially affected by domain switching. Under high electrical and/or mechanical external fields, the state of polarization and remanent strains is substantially changed at the crack tip. These irreversible dissipative processes influence the fracture toughness of the cracked ferroelectric material. In the present paper, the micromechanical domain switching processes at the crack tip are studied by numerical simulation and compared with the in situ experimental results obtained by Jones et al. (Acta Mater 55(16):5538–5548, 2007) using X-ray diffraction analyses in synchrotron. Main attention is payed to the spatial distribution of preferred domain orientation in a mechanically loaded compact tension specimen made of a soft tetragonal lead zirconate titanate ceramics. It is found that the mechanically induced favored domain orientation distribution depends on position within the plane of the CT specimen and correlates with projected deviatoric stresses and strains. Some issues concerning shortcomings in the experimental and simulation results are raised and discussed. The outcome of this type of simulations forms the basis for more realistic fracture mechanical evaluations in future.
关键词： Domain switching,Crack tip,Ferroelectric/piezoelectric materials,Fracture,Process zone
更新于2025-09-23 15:23:52
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Ferroelectric Polarization-Switching Dynamics and Wake-Up Effect in Si-Doped HfO <sub/>2</sub>
摘要： Ferroelectricity in ultra-thin HfO2 offers a viable alternative for ferroelectric memory. Reliable switching behavior is required for commercial applications; however, the many intriguing features of this material have not been resolved. Herein, we report an increase in the remnant polarization after electric field cycling, known as the 'wake-up' effect, in terms of the change in the polarization switching dynamics of a Si-doped HfO2 thin film. Compared with a pristine specimen, the Si-doped HfO2 thin film exhibited a partial increase in polarization after a finite number of ferroelectric switching behaviors. Polarization switching behavior was analyzed using the nucleation-limited switching model characterized by a Lorentzian distribution of logarithmic domain-switching times. The polarization switching was simulated using the Monte Carlo method with respect to the effect of defects. Comparing the experimental results with the simulations revealed that the wake-up effect in HfO2 thin film is accompanied by the suppression of disorder.
关键词： Domain switching,Ferroelectricity,Defects,FeRAM,HfO2,Thin films
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE ISAF-FMA-AMF-AMEC-PFM Joint Conference (IFAAP) - Hiroshima (2018.5.27-2018.6.1)] 2018 IEEE ISAF-FMA-AMF-AMEC-PFM Joint Conference (IFAAP) - Domain Switching by Applied Electric Field in (001) and (111)-epitaxial (K<inf>0.5</inf>Na<inf>0.5</inf>)NbO<inf>3</inf>Films
摘要： (K1-xNax)NbO3 (KNN) is especially paid attention to as a lead-free piezoelectric material. It is known that KNN has a morphotropic phase boundary (MPB) at x ~ 0.5, which shows a high piezoelectric property. However, it has not been fully clarified how the domain structure of KNN changes by applied electric field. In this study, we observed electric field-induced strain and domain fraction change of KNN films by synchrotron X-ray diffraction.
关键词： Na)NbO3,domain switching,films,(K
更新于2025-09-23 15:23:52
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Domain and Switching Control of the Bulk Photovoltaic Effect in Epitaxial BiFeO3 Thin Films
摘要： Absence of inversion symmetry is the underlying origin of ferroelectricity, piezoelectricity, and the bulk photovoltaic (BPV) effect, as a result of which they are inextricably linked. However, till now, only the piezoelectric effects (inverse) have been commonly utilized for probing ferroelectric characteristics such as domain arrangements and resultant polarization orientation. The bulk photovoltaic effect, despite sharing same relation with the symmetry as piezoelectricity, has been mostly perceived as an outcome of ferroelectricity and not as a possible analytical method. in this work, we investigate the development of BpV characteristics, i.e. amplitude and angular dependency of short-circuit current, as the ferroelastic domain arrangement is varied by applying electric fields in planar devices of Bifeo3 films. A rather sensitive co-dependency was observed from measurements on sample with ordered and disordered domain arrangements. Analysis of the photovoltaic response manifested in a mathematical model to estimate the proportion of switched and un-switched regions. the results unravel the potential utility of BPV effect to trace the orientation of the polarization vectors (direction and amplitude) in areas much larger than that can be accommodated in probe-based techniques.
关键词： BiFeO3,ferroelectricity,polarization orientation,domain switching,bulk photovoltaic effect
更新于2025-09-16 10:30:52
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Electric-field-controllable nonvolatile multilevel resistance switching of Bi <sub/>0.93</sub> Sb <sub/>0.07</sub> /PMN-0.29PT(111) heterostructures
摘要： Electric-field switchable multilevel nonvolatile resistance states are achieved at room temperature in Bi0.93Sb0.07/0.71Pb(Mg1/3Nb2/3)O3-0.29PbTiO3(111) (PMN-0.29PT) heterostructures. During the initial poling of the PMN-0.29PT, the variation of the resistance of the Bi0.93Sb0.07 film with the electric field tracks the variation of the electric-field-induced in-plane strain of the PMN-0.29PT effectively, revealing that the resistance switching is dominated by the ferroelectric-domain-switching-induced lattice strain but not the domain-switching-induced polarization charges. A relative resistance change DR/R ≈ 7% at 300 K and up to ≈10% at 180 K were achieved near the coercive field EC of the PMN-0.29PT(111) substrate. At least five stable resistance states with good endurance properties could be obtained at room temperature by precisely controlling the electric-field pulse sequence as a result of the nonvolatile remnant strain transferring from the PMN-0.29PT to the film, providing a simple and energy efficient way to construct multistate resistive memory.
关键词： Bi0.93Sb0.07/PMN-0.29PT(111) heterostructures,nonvolatile,multilevel resistance switching,ferroelectric-domain-switching-induced lattice strain,electric-field
更新于2025-09-10 09:29:36
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Ferroelectricity mediated by ferroelastic domain switching in HfO <sub/>2</sub> -based epitaxial thin films
摘要： Herein, ferroelastic domain switching from the nonpolar b-axis to the polar c-axis oriented domain in ferroelectric ?lms is demonstrated. Scanning 7%-YO1.5-substituted HfO2 (YHO-7) epitaxial transmission electron microscopy (STEM) indicates that the polarization of a pristine ?lm deposited on a Sn-doped In2O3/(001)YSZ substrate by the pulsed laser deposition method tends to be along the in-plane direction to avoid a strong depolarization ?eld with respect to the out-of-plane direction. Applying an electric ?eld aids in ferroelastic domain switching in YHO-7 ?lms. Such ?lms exhibit ferroelectric characteristics with a relatively large saturated polarization around 30 lC/cm2 by polarization reorientation from the in-plane to the out-of-plane directions and an increased dielectric constant. The synchrotron X-ray diffraction measurements with a focused beam for the pristine and poled area indicate ferroelastic 90(cid:2) domain switching as the odd number re?ection disappears, which is only allowed in the nonpolar b-axis orientation. STEM observations also show a signi?cant increase in the c-axis oriented domain. This observation of ferroelastic domain switching strongly supports the conclusion that the ferroelectricity of HfO2 originates from the non-centrosymmetric orthorhombic phase.
关键词： ferroelectricity,ferroelastic domain switching,epitaxial thin films,HfO2
更新于2025-09-10 09:29:36
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Effect of large-scale domain switching on intensity factors for a crack in 3D ferroelectric single crystals using the I-integral method
摘要： Due to their intrinsic brittleness, ferroelectric materials are prone to fracture under extreme electromechanical operational loads. The fracture of ferroelectric materials is usually accompanied by large-scale domain switching. This paper develops the interaction integral (I-integral) method for a crack in three-dimensional ferroelectrics through applying a virtual load increment to the current state. Unlike the widely-used switching-toughening model, the I-integral is not restricted to small scale switching. Due to designable choice of the virtual load increment, the I-integral allows to decouple the intensity factors of different fracture modes. The local intensity factors along the curved crack front can be directly extracted, since the I-integral is independent of integration volume. With these merits, the I-integral method is a very promising technique in fracture analysis of ferroelectrics under large-scale domain switching. Moreover, the I-integral method is used in combination with the phase field model to simulate a tensile test of nanoscale PbTiO3 ferroelectric single crystal with a semi-circular surface crack. Results show that various patterns of polarization pairs appear as soon as the applied load is increased beyond a critical value. The stable domain structures are divided into two layers by the plane where the crack is located and in each layers several polarization vortices formed eventually. Apart from the geometry and loading conditions, the position where the crack front is located with respect to the polarization vortex is a key factor affecting the switching-induced change of the stress intensity factor.
关键词： crack,interaction integral (I-integral),large-scale domain switching,phase field model,ferroelectric,intensity factor
更新于2025-09-10 09:29:36
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Transparent tetragonal-cubic zirconia composite ceramics densified by spark plasma sintering and hot isostatic pressing
摘要： Targeting higher toughness transparent ceramics, tetragonal (3 mol % yttria) and cubic (8 mol % yttria) ZrO2 starting powder mixtures were densified by spark plasma sintering (SPS) in vacuum at 1100°C and post hot isostatic pressing (HIP) in argon at 1100°C. The influence of the ultra-fine microstructure and phase composition on the fracture resistance and light transmission in the visible and infra-red range was assessed. Of special interest was the influence of a thermal annealing step in air on the transparency of the SPS and SPS-HIP ceramics.
关键词： Total Forward Transmission,Hot Isostatic pressing,Spark Plasma Sintering,Ferro-elastic domain switching,Transparent zirconia
更新于2025-09-10 09:29:36