BaTiO3–Epoxy–ZnO-Based Multifunctional Composites: Variation in Electron Transport Properties due to the Interaction of ZnO Nanoparticles with the Composite Microstructure

Abstract

Piezoelectric and electro-active composites are being investigated as a generation of self-powered energy harvesting devices for a wide range of applications. More specifically, three-phase piezoelectric composites are capable of maintaining high reliability, durability, and sensitivity, all while being economically feasible and nontoxic. In addition, three-phase composites can be tailored towards multifunctional applications depending on which material is incorporated as the third-phase. The criteria that governs the applicability of these composites depend upon their electromechanical properties such as their impedance, resistivity, conductivity, and dielectric constant. Therefore, the present work involves the fabrication of barium titanate-epoxy-zinc oxide (BT-Ep-ZnO) multifunctional composites, and the study of the variation of their electron transport properties. The volume fraction of BT was held constant at 0.40, while the volume fraction of ZnO was varied from 0.01 to 0.10. The dipoles of the electro-active phases were aligned using a contactless corona plasma discharge poling technique. The impedance, resistance, conductance, and capacitance were measured over a frequency range of 20 Hz to 10 MHz. The geometry of the composites was measured and used to normalize the data by calculating the resistivity, conductivity, and dielectric constant. The piezoelectric strain coefficients, d33 and d31, were measured using a piezometer at a frequency of 110 Hz. The fractured surface morphology and distribution of the particles were observed with a scanning electron microscope.

Chitosan-ZnO Nanocomposites Assessed by Dielectric, Mechanical, and Piezoelectric Properties

“…Moreover, in polymer nanocomposites with NPs with high dielectric constant (such as PZT, BaTiO 3, BZT) there is an increase of d 33 with an increase of the dielectric constant with NPs content [ 74 , 75 , 76 ]. However, in BaTiO 3 -epoxy-ZnO (with a fixed concentration of BaTiO 3 ) [ 77 ] and PVDF-ZnO [ 56 ], the dependences of the piezoelectric coefficient and the dielectric constant on the concentration of ZnO exhibit a maximum (similarly to the maximum presented in Figure 4 b). This maximum cannot be explained by classical conductivity percolation effect because the conductivity of CS-ZnO films decreases with ZnO NPs wt.% ( Figure 4 a).…”

Fabrication and Characterization of Flexible Three-Phase ZnO-Graphene-Epoxy Electro-Active Thin-Film Nanocomposites: Towards Applications in Wearable Biomedical Devices

“…At the lower frequencies, space charges are the dominant phenomenon for electron transport and Graphene nanoplatelet clusters and agglomerations play a major role in enhancing electron mobility in the nanocomposite [37]. When the frequency reaches the megahertz range, the anisotropic nature of the ZnO wurtzite structure further contributes to the increase in the electron mobility by localized dipoles [33]. This also reduces electron scattering in the insulative epoxy matrix due to additional electron transport regimes.…”

“…At the lower VFs, the increase in the ZnO VF leads to an increase in Z" values due to the encapsulation of localized Graphene percolation pathways with the ZnO clusters. Beyond a ZnO VF of 0.3, electron transport is increased through the increased surface area of the ZnO clusters which enhanced the electron mobility through electron hopping and direct-contact electron transport mechanisms [33]. With an increase in the VF to 0.7, an increase the Z" values and a drop in the conductivity values points to the increased contact resistance between the different ZnO clusters and also the insulative epoxy matrix which leads to a lower dielectric constant and adversely affects the direct-contact electron transport mechanism [33].…”

“…For each VF, The flexibility of the ZnO nanocomposite is added through the epoxy matrix phase [30][31][32]. As a result of incorporating the epoxy phase in the ZnO phase, the electric and dielectric properties of the nanocomposite are negatively affected by the insulative matrix material [33]. The integration of graphene and other carbon-based nanomaterials can enhance the electrical properties [34,35], thermal properties [36], and also add flexibility and strength to the composite [37].…”

Factors affecting the piezoelectric performance of ceramic-polymer composites: A comprehensive review

“…In order to further enhance the dielectric properties of biphasic composites, several approaches based on including a third phase to the composite have been exploited [133], [134] such as the addition of conductive particles to the two-phase piezoelectric system [135]. Insight from literature highlighted that the addition of conductive carbon black particles to a PZT-PVDF composite resulted in an enhanced d33 of 42pC/N (at a composition of 0.7PZT/0.3PVDF and 0.4% carbon black) at 1kHz when compared to a d33 of 23pC/N for the same system but without carbon black inclusions [136].…”