Abstract
It has been reported that the flexoelectric effect could be dominant in the nanoscale. The discrepancy between theory and experiments on the frequency dependence of the dielectric constant of an ordered assembly of BaTiO3 nanocubes is nearly resolved by assuming the coexistence of flexo- and ferro-electric effects. Although flexoelectric polarizations perpendicular to the applied alternating electric field contribute to the dielectric constant, those parallel to the electric field do not contribute because the magnitude of the flexoelectric polarization does not change due to the mismatch of strain at the interface of the nanocubes. On the other hand, some dielectric response is possible for the ferroelectric component of the polarization parallel to the electric field.
Highlights
To develop thinner high-performance smartphones and wearable devices, such as eyeglass-type and wristwatch-type, miniaturization and improvement of the properties of dielectric devices such as multilayer ceramic capacitors (MLCCs) are required
Flexoelectric polarization parallel to the applied alternating electric field does not contribute to the dielectric constant
As four vectors of flexoelectric polarization in one nanocube are perpendicular to the applied electric field, and the other two vectors are parallel to the applied electric field under the configuration of Figure 1, the averaged dielectric constant (ε) for an ordered assembly of BaTiO3 nanocubes is assumed to be given as follows under a constant temperature
Summary
To develop thinner high-performance smartphones and wearable devices, such as eyeglass-type and wristwatch-type, miniaturization and improvement of the properties of dielectric devices such as multilayer ceramic capacitors (MLCCs) are required. The measured dielectric constant was about 3800 and 2600 for 290- and 580-nm-thick assemblies, respectively, at 1 MHz at room temperature [5,6] For both thicknesses, the amplitude of the applied alternating electric voltage was the same as 0.5 V. The temperature dependence of the dielectric constant of an ordered assembly of BaTiO3 nanocubes is reproduced by numerical calculations. Flexoelectric polarization parallel to the applied alternating electric field does not contribute to the dielectric constant. The ferroelectric component of polarization parallel to the applied alternating electric field contributes to the dielectric constant. The coexistence of flexo- and ferro-electric effects almost resolves the discrepancy between theory and experiment on the frequency dependence of dielectric constant of an ordered assembly of BaTiO3 nanocubes, which is an improvement compared to Ref. In the present ODE model, the nonlinear effect is taken into account by using the nonlinear potential
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