Study of the role of porosity on the functional properties of (Ba,Sr)TiO 3 ceramics

The role of porosity on the low and high field dielectric properties was studied in Ba0.70Sr0.30TiO3 ceramics with various porosity levels obtained by using lamellar graphite as sacrificial template. The permittivity decreases with increasing porosity, from around ε ∼ 7690 (dense ceramic) down to 380 (ceramic with 29% porosity), while preserving the Curie temperature at about 35 °C. The effective permittivity was discussed by using Effective Medium Approximation and Finite Element Method approaches. The role of porosity and specific microstructural characteristics induced by the pore forming addition, from closed porosity (0–3) towards a combined (0–3, 2–2) with lamellar-type of microstructures for the most porous ceramics was taken into consideration. All the investigated ceramics preserve a high level of tunability as in the dense material, irrespective of the porosity level, while the zero field permittivity was decreased to a few hundreds.