Models for the frequency dependence of coercive field and the size dependence of remanent polarization in ferroelectric thin films

We have confirmed the theory of Ishibashi and Orihara for the frequency dependence of coercive fields in ferroelectric thin films.SrBi2NbTaO9, SrBi2Ta2O9, and PbZr1-x Ti x O3 (PZT) data from DeVilbis et al. reveal a power-law dependence of form Ec (f) = Bfd/α , where d is the dimensionality of domains (ca. unity in uniaxial ferroelectrics such as SBT and SBNT) and α is approximately 6, in agreement with theoretical predictions. Models are also presented for the polarization and fatigue data from NEC of micron-sized thin-film strontium bismuth tantalate capacitors, emphasizing behaviour at unsaturated voltages.