Polarization behavior of ferroelectric multilayered composite structures

Tsang

2004

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We model the dynamic polarization behavior of ferroelectric films by an analytical approach. Using a parallelogramlike P-E hysteresis model, explicit expressions were obtained for describing the D-E loops of ferroelectric films as would be measured from a Sawyer-Tower circuit. By introducing the consideration of electrical conduction, resistive losses inflate the ferroelectric loop to some extent. In addition, an asymmetric conduction will result in polarization offsets with the magnitude and direction depending on the asymmetric conductivities of the materials. The inflated loop, as well as the offset phenomena, which have been observed experimentally ͓e.g., L. Zheng, C. Lin, W.-P. Xu, and M. Okuyama, J. Appl. Phys. 79, 8634 ͑1996͔͒, will be discussed by means of our modeled results. Some simple exact formulas have been derived and the effects of electric, dielectric, and ferroelectric parameters, as well as the applied field on the ''apparent'' polarization were also examined.

Section: B Polarization Offsets In Ferroelectrics With Asymmetric Comentioning

confidence: 99%

Explicit expressions for the dynamic polarization behavior in ferroelectrics with symmetric/asymmetric electrical conductivity

Tsang

2004

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“…Indeed, we have also found that this hypothesis remains valid for other loop shapes, as we have numerically performed the above analysis with a more realistic hysteresis model of a different loop shape. 30 On the other hand, when the P-E hysteresis loop of each constituent has a "symmetric" shape, i.e., P͑E͒ =−P͑−E͒, for the increasing and decreasing field branches, Eq. (12) seems to be satisfied for any combination of the constituents.…”

Section: ͵ T Eamentioning

confidence: 99%

“…For materials with a smoother polarization gradient, a multilayered structure 30 with a sufficient number of layers should be employed. On the other hand, our analytical formulation is also suitable for the study of the behavior of other ferroelectric layered structures.…”

Section: ͵ T Eamentioning

confidence: 99%

Modeling of anomalous shift and asymmetric hysteresis behavior of ferroelectric thin films

2004

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Surface acoustic wave micromotor with arbitrary axis rotational capability Appl. Phys. Lett. 99, 214101 (2011) Dielectric model of point charge defects in insulating paraelectric perovskites J. Appl. Phys. 110, 094110 (2011) A correlated electron diffraction, in situ neutron diffraction and dielectric properties investigation of poled (1-x)Bi0.5Na0.5TiO3-xBaTiO3 ceramics J. Appl. Phys. 110, 084114 (2011) Domain size engineering in tetragonal Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 crystals J. Appl. Phys. 110, 084110 (2011) Influence of the critical point on the electrocaloric response of relaxor ferroelectrics J. Appl. Phys. 110, 064118 (2011) Additional information on J. Appl. Phys. An analytical bilayer model has been developed to consider the effect of the existence of a dead layer (e.g., due to polarization degradation) at the film-electrode interface in an otherwise homogeneous ferroelectric thin film. By introducing asymmetric conductivity in the dead layer, the anomalous horizontal (along the field axis) shift behavior of hysteresis loops in ferroelectric thin films is successfully reproduced. Assuming that the ferroelectric P-E hysteresis loops of the layers are parallelogramlike, explicit expressions are derived for calculating the internal fields in the film, as well as the "apparent" D-E loop as measured from a Sawyer-Tower circuit. The general switching sequence for the ferroelectric phases will be considered. Using the ferroelectric-ferroelectric bilayer model, other anomalous phenomena, including vertical shift and deformed loop shape are also modeled.

“…Therefore, an elaborate ferroelectric hysteresis model capable of modeling saturated and unsaturated loops in arbitrary fields is an essential tool to such a study. The model of Miller et al, 5 adopted in our previous works to study ferroelectric films and composites, [6][7][8] can in principle simulate unsaturated hysteresis loops. This model is computationally efficient and most of the general features of hysteresis behavior in ferroelectrics can be reproduced.…”

Section: Introductionmentioning

confidence: 99%

Modeling of bias-field-dependent dielectric properties in ferroelectric thin films

Tsang

2005

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The bias-field-dependent dielectricity of ferroelectric thin films is studied by use of a multilayer model capable of modeling saturated and unsaturated hysteresis behavior under arbitrary fields. The simulated minor hysteresis loops at different bias fields are used to calculate the variation of dielectric permittivity with the bias field. The -E loops show asymmetric shifting along the field axis when the film is assumed to possess a secondary dielectric layer with trapped charge. Simulated D-E and -E loops are compared with the experimental data on barium zirconate titanate and lead zirconate titanate thin films. In general, the model predictions show reasonably good agreement with experiment. Effects of charge density and the ac measurement field amplitude on the measured permittivity, as well as the dielectric tunability have also been examined.