Processing and properties of porous piezoelectric materials with high hydrostatic figures of merit

Porous piezoelectric materials are of interest for applications such as low frequency hydrophones. This is due to their high hydrostatic figures of merit and low sound velocity, which leads to reduced acoustic impedance and enhanced coupling with water or biological tissue. A wide variety of methods are available to produce porous structures such as using reticulated polymer foams or volatile additives which are burnt out during the sintering process (e.g. polymer spheres). Each processing technique and additive produces its own distinctive microstructure, particularly in terms of pore size, morphology and porosity volume fraction. The aim of this paper is to manufacture a variety of porous microstructures and relate the structures to measured hydrostatic figures of merit.