Piezoelectric performance of PZT-based materials with aligned porosity: experiment and modelling

A new micromechanical model is proposed to analyse the piezoelectric properties of freeze-cast porous composite materials based on a ferroelectric lead zirconate titanate-type (PZT) ceramics. The important influence of the composite microgeometry and the porous ceramic matrix on the piezoelectric coefficients d^∗ _3j and g^∗ _3j and the piezoelectric anisotropy factor d^∗ ₃₃/|d^∗ ₃₁ in the porosity range of m_p = 0.2-0.6 is evaluated and discussed. The resulting piezoelectric parameters of parallel-connected freeze-cast composites with highly aligned pore channels are then compared to those of PZT-based porous materials with randomly distributed porosity. Due to the relatively large piezoelectric coefficients d^∗ ₃₃ ∼ 10² pC N^-1, g^∗ ₃₃ ≈ 40-100 mV m N^-1, anisotropy factor d^∗ ₃₃/|d^∗ ₃₁ ≈ 3-5 and the presence of aligned porous channels, the parallel-connected freeze-cast composite has advantages over conventional monolithic PZT-type ceramics (e.g. g ₃₃ = 24.2 mV m N^-1 and d ₃₃/|d ₃₁| = 2.2 in the PZT-5 ceramic) and is suitable for piezoelectric transducer, sensor, acoustic, and energy-harvesting applications.