Model for grain size effect on dielectric nonlinearity of ferroelectrics

Dielectric nonlinearity is an important characteristic of ferroelectrics. It is assumed that in ferroelectrics the grains are all uniform, in order and cubic-shaped. Moreover, the dielectric constant of the grain boundary does not vary with direct current bias. And then the grains and the grain boundaries were modeled in terms of capacitors and resistors. Based on these analyses, a model for grain size effect on dielectric nonlinearity of ferroelectrics was established. In this model there are some parameters such as the grain size and the grain boundary width, which intensively influence on the dielectric properties of ferroelectric ceramics and thin films. The accuracy of the model prediction was quantitatively verified by our experimental data. The results proved that the above model can describe the grain size effect on dielectric nonlinearity of ferroelectrics.