Modeling the dielectric response of incipient ferroelectrics

Interest in incipient ferroelectrics has been renewed due to their promise for applications at cryogenic temperatures. The dependence of the dielectric constant of an incipient ferroelectric on temperature and the applied biasing field can be modeled correctly by solution of the Ginsburg-Devonshire equation. A set of simple and correct formulas is derived to provide simulation of the dielectric constant of an incipient ferroelectric as a function of temperature and the biasing field. As a typical representative of this, SrTiO3 is used. The inhomogeniety of the composition or/and structure of the material is quantitatively described by a specially introduced coefficient. The correlation effect is used to describe the size effect for a thin film capacitor. The boundary conditions for a ferroelectric polarization on the surface of electrodes are considered, The boundary conditions are specified for the interface between the ferroelectric and the metal or the high temperature superconductor. Comparison of the simulated and experimental data for both the bulk sample and for the thin film capacitor shows good numerical agreement. The model is intended to be used for developing the computer aided design of microwave components and devices based on ferroelectric films. (C) 1997 American Institute of Physics. [S0021-8979(97)03021-1].