Role of the pore interconnectivity on the dielectric, switching and tunability properties of PZTN ceramics

The influence of phase interconnectivity in porous Pb-0.988(Zr0.52Ti0.48)(0.976)Nb0.024O3 ceramics on the structural, dielectric and tunability properties is reported. Porous ceramics with the same porosity level, but with different types of pore interconnectivity (0-3) and (3-3) type have been prepared by using dry and wet mixing of perovskite powder with starch porosity former agent. By comparison to the dense sintered ceramic (predominantly tetragonal), high porosity tends to favour the formation of monoclinic phase on the expense of the tetragonal one. A strong decrease of the effective permittivity with respect with the dense ceramic in both the porous structures was found, with lower values for the (3-3) connectivity. To describe the observed role of the phase interconnectivity on the dielectric properties, Finite Element Modeling calculations were performed. The local boundary conditions for such specific configurations generate a local field inhomogeneity, with a broad field distribution and decrease of the average field, which is more pronounced in the (3-3) porous configuration. As result, a strong decrease of the effective permittivity, switching polarization, loop area and rectangularity factor are predicted for this configuration, and confirmed by high-field experiments (tunability epsilon(E) and P(E) ferroelectric loops). This study shows that not only the pore amount, but the pore interconnectivity has a major role on the electrical properties and well-designed phase interconnectivity may provide useful functional properties.