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

Abstract

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.

Dependence of polarization offset on driving frequency, film thickness and composition gradient in compositionally graded ferroelectric materials

“…When the frequency f * is larger than 0.1, the modeled hysteresis loop is very symmetrical and centered at the origin of the axes, while the simulated hysteresis loop will become significantly distorted if f * < 0.005. This agrees with the analysis reported by Wong et al [7]. Since the dynamic shifting effect is highly related to the temporal characteristic of the TDSCL conduction, a frequency dependence of the rate of approach to the steady state offset is expected.…”

Ferroelectric properties of compositionally graded BST ceramics

“…We would like to note that a number of authors, when interpreting experimental data on graded thin films, have doubts about the intrinsic nature of the effects connecting them with the asymmetrical leakage currents [24,25]. The materials studied in our work had high enough direct current (DC) resistivity ( % 2 Â 10 11 m) that did not depend on the polarity of the applied field.…”

Origin of the linear term in the pseudo-spin Hamiltonian of compositionally graded ferroelectrics

“…Since publishing of the pioneering work [1] many papers [2][3][4][5][6][7][8][9][10][11][12][13][14][15] have been devoted to investigation of compositionally graded ferroelectrics (CGF). One of the most interesting results of experimental observation on CGF is discovery of a new type of the pyroelectric effect.…”