Finite element modelling of bilayer porous PZT structures with improved hydrostatic figures of merit

A finite element model is presented in which bilayer lead zirconate titanate (PZT) structures that are formed from a dense layer and a porous layer are investigated for their hydrostatic sensing properties. The model simulates the poling of the porous ferroelectric material to determine the distribution of poled material throughout the structure. The fraction of PZT successfully poled is found to be closely related to resulting piezoelectric and dielectric properties of the composite. Structures with high layer porosity (>40 vol.%) and porous layer relative thickness (>0.5) were found to have a significantly improved hydrostatic piezoelectric coefficient, dh, hydrostatic voltage coefficient, gh, and hydrostatic figure of merit, dh.gh. The highest dh.gh of 7.74 × 10⁻¹² m²/N was observed in the structure with a porous layer relative thickness of 0.6 and porosity of 60 vol.%, which was more than 100 times higher than that for dense PZT (dh.gh = 0.067 × 10⁻¹² m²/N) and over three times that of PZT with 60 vol.% porosity with 3-3 connectivity (dh.gh = 2.19 × 10⁻¹² m²/N). The results demonstrate the potential for layered porous materials for use in hydrophones.