Investigation into the dynamic molecular and conductivity mechanisms of piezoelectric ceramics Pb[Zr_xTi_1−x]O₃/epoxy piezocomposites

Abstract Throughout this work, an experimental and theoretical analysis of the molecular dynamics, correlated with the alternating current conductivity σ_ac(ω, T),of unidirectional piezoelectric composites used as actuators and/or sensors in different systems was carried out. The 3D‐representation of the imaginary part M″(ω, T) of the electric modulus shows, apart from the presence of the classical secondary β and the primary α dipolar relaxation processes, the appearance of a new peak attributed to the Maxwell‐Wagner‐Sillars (MWS) interfacial polarization whose amplitude depends on the rate of reinforcement. In our case, since we are usually within the range of fragile materials, the stiffness of the 26% fiber content composite is about 4.5 times greater than that of 13.4% (via the fragility parameter D), shows a less pronounced curvature and the nature of the relaxation times is closer to the Arrhenius type. Due to the high dispersion of the conductivity with the frequency of applied electrical field in the range (1‐10⁴ Hz), Jonscher's “universal power law” has been revised by adding a new term, which takes into account the displacement current density. The ac conductivity adjustment procedure, using the new obtained expression, turns out to be accurate and follows the experimental data reported in the low, high, and even intermediate frequency domains. This theoretical approach allowed us to determine the key parameters (∆ε, τ_max,…) unique to each relaxation process, and to demonstrate the MWS interfacial polarization that is directly linked to the adhesion between the PZT fibers and the epoxy resin matrix.