Grain size dependence of the rayleigh coefficients in barium titanate ceramics

Grain size dependence of the initial dielectric constant and Rayleigh coefficients of BaTiO 3 ceramics with grain sizes from 0.5μm to 20μm have been studied. A region of Rayleigh law validity was observed for each grain size. The initial dielectric constant show a maximum for the ceramic with 2.5μm grain size and the Rayleigh coefficient increases with increasing the grain size. Using a statistical theory of the low field P(E) loop and the hypothesis of a maximum domain wall density at a critical grain size in ceramics, theoretical grain size dependencies with maxims for both the initial dielectric constant ϵ in (g) and Rayleigh coefficient a(g) have been derived.