A novel method based on the Virtual Particle Mori–Tanaka (VPMT) is developed to predict the effective electro-elastic properties, d₃₃ and g33, of structured piezoelectric particulate composites with improved accuracy by means of a single parameter related to the spatial distribution of imperfectly aligned rod-like PZT particles. The VPMT method is found to have excellent prediction capabilities for idealized particle configurations. Several new correction functions are presented to capture the drop in piezoelectric composite’s electro-elastic properties as a function of topological imperfections. These imperfections are related to longitudinal and lateral inter-particle spacings and the topology of the chain like structures themselves. The functions are evaluated in detail and show physically consistent behaviour.

The need for flexible, highly sensitive tactile sensors that can fit onto curved surfaces is driving the conformable sensor materials research in the field of human–machine interactions. Here we report a new type of compliant piezoelectric active composite, a micro-porous polyurethane-PZT material, capable of generating a voltage output upon touch. The composites are synthesized with the aim of maximizing the piezoelectric sensitivity of particulate composite sensor materials. The goal is to reduce the dielectric constant of the polymer matrix and improve flexibility of conventional bulk piezo-composites, consisting of ceramic particles in a dense polymeric matrix, by adding a third (gaseous) phase to the system in the form of uniformly sized pores. The presence of the gaseous component in the polymer matrix in the form of well-distributed spherical inclusions effectively decreases the polymer dielectric permittivity, which increases the piezoelectric voltage sensitivity (g₃₃) of the composite sensors significantly. The unique combination of dielectrophoretic structuring of PZT particles and the addition of a gaseous phase to the polymer resin results in the highest performance of the particulate composite sensors reported in the literature so far. The newly developed micro-porous composites show g₃₃ value of 165 mV m/N that is twice that of the structured PZT-bulk PU composites (80 mV m/N) and more than five times the g₃₃ value of bulk PZT ceramics (24–28 mV m/N). The capability of the flexible freestanding sensors for application in touch sensing devices for soft robotics is demonstrated.

Tri-phase PZT-porous polyurethane (PU) composites are investigated with the aim of developing conformable, highly sensitive tactile sensors for application in Human-Machine Interactions. The main goal is to reduce the dielectric constant of the polymer matrix, and improve flexibility of traditional diphase piezo-composites, consisting of ceramic particles in a dense polymeric matrix, by adding a third (gaseous) phase to the system. The presence of the gaseous component in the polymer matrix in the form of well-distributed spherical inclusions effectively decreases the polymer dielectric permittivity, which improves the piezoelectric voltage coefficient of the composites significantly. The unique combination of dielectrophoretic structuring of PZT particles and the addition of a gaseous phase to the polymer resin results in the highest performance of the particulate composite sensors reported in the literature so far. The g₃₃ values of the newly developed triphase composites are twice that of the structured di-phase PZT-dense PU composites (80 mV.m/N) and more than five times the g₃₃ value of bulk PZT ceramics (24-28 mV.m/N).

The effects of Zr/Ti ratio on the dielectric and piezoelectric properties of the sintered Pb(Zr_xTi_(1−x))_0.99Nb_0.01O₃ piezoelectric ceramics across the entire range of phase diagram of the PZT solid solution was studied systematically. The materials were prepared by the conventional mixed oxide process. The phase purity and crystal structure of the calcined powders and sintered ceramics was analysed using X-ray diffraction. The microstructure of the sintered ceramics has been investigated using scanning electron microscopy. It is seen that even though there is a significant increase in dielectric constant (ϵ_r) and piezoelectric charge coefficient (d₃₃) at the PZT-52 (MPB) composition, the voltage sensitivity (g₃₃) of the PZT-0 (lead titanate) ceramics are higher than that of MPB.