Influence of charged defects on the dielectric response of incipient ferroelectrics

Charged grain boundaries between crystalline blocks in bulk and thin film samples of incipient ferroelectrics are considered as charged defects producing a built-in electric field which is treated as a statistical dispersion of the biasing field. The normalized statistic dispersion of a biasing field, denoted as ξS, is used as one of the parameters of a phenomenological model of the dielectric response of incipient ferroelectrics. The surface charge density on the grain boundary is quantitatively estimated on the basis of a multiple-scattering analysis of spatially resolved electron-energy-loss spectra of the boundary between crystalline blocks in SrTiO3. The built-in electric field in the incipient ferroelectrics is quantitatively estimated by the parameter ξS which determines some specific features of the dielectric response of the incipient ferroelectric single crystal and thin film samples.