Temperature Dependence of the Dielectric Permittivity of BaTiO3-CoFe2O4 Ceramic Composites.

Two-phase ceramic composites of cobalt ferrite dispersed in a barium titanate matrix were prepared and their dielectric permittivity was characterized. A rounding of their dielectric constant near the ferroelectric transition temperature of the BaTiO3 phase was observed. A generalized brick-wall model, taking into account the BaTiO3 contribution, fitted with the Landau-Devonshire theory, and the CoFe2O4 permittivity, experimentally determined, was used in order to obtain their effective dielectric constant. The effective model was applied to the discussion and fitting of the temperature dependence of the dielectric permittivity of the composites. The Landau-Devonshire coefficients for the BaTiO3 phase were also obtained. [ABSTRACT FROM AUTHOR]