Characterisation of porous PZT ceramics by first-order reversal curves (FORC) diagrams

The method of investigation based on the first-order reversal curves (FORC) is proposed for describing the role of porosity on the switching properties of Nb–PZT ceramics with anisotropic porosity prepared using lamellar graphite as pore-forming agent. The experimental FORC diagrams have two distinct parts attributed to the reversible and irreversible components of the ferroelectric polarization. A more localized distribution was found in the dense material, while in the porous one (40% porosity) the distribution is broad and spread towards higher fields, due to the local depolarising field created at the boundaries. The FORC susceptibilities indicate the degree of tunability of the permittivity under the applied field. In this analysis it was found that porosity has a detrimental effect on the tunability of the system in the same range of the electrical fields.