Piezoelectricity refers to the phenomenon where mechanical stress is converted into electrical signals or, conversely, electrical signals are converted into mechanical stress. Ferroelectric materials, characterized by high dielectric permittivity and spontaneous polarization, retain their polarization even after the removal of an electric field. In such materials, poling plays a crucial role in enhancing the piezoelectric effect, with the process of aligning dipoles being known as poling. This review focuses on studies that have compared and analyzed the enhancement of piezoelectric properties in ceramics and polymers through two representative poling methods: AC poling (ACP) and DC poling (DCP). Even within the same category of ceramics or polymers, variations in piezoelectric properties are observed based on the material type, poling method, and poling conditions. Under certain conditions, ACP has been shown to provide superior poling effects compared to DCP. Through this review, we propose that ACP has the potential not only to replace the traditionally used DCP in the poling of piezoelectric materials but also to serve as a more effective method. This could spark increased interest in the study of poling methods for piezoelectric polymers, a field that has received relatively less attention.

Electrical poling is a crucial step to convert ferroelectrics to piezoelectrics. Nevertheless, no systematic investigation on the effect of poling has been reported. Given that the poling involves an alignment of spontaneous polarization, the condition for poling should be different when a material has an internal bias field that influences the domain stability. Here, we present the effect of poling profile on the dielectric and piezoelectric properties in Mn-doped Pb(Mg_1/3Nb_2/3)O₃-29 mol%PbTiO₃ single crystal with an internal bias field. We showed that both the dielectric permittivity and the piezoelectric coefficient were further enhanced when the poling procedure ends with a field application along the opposite direction to the internal bias field. We expect that the current finding would give a clue to understanding the true mechanism for the electrical poling.

Ferroelectric material properties are strongly governed by domain structures and their evolution processes, but the evolution processes of complex domain patterns during a macroscopic electrical poling process are still elusive. In the present work, domain-evolution processes in a PZT ceramic near the morphotropic phase-boundary composition were studied during a step-wise electrical poling using piezoresponse force microscopy (PFM). Electron backscatter diffraction was used with the PFM data to identify the grain boundaries in the region of interest. In response to an externally the applied electric field, growth and retreat of non-180° domain boundaries wasere observed. The results indicate that ferroelectric polarization-switching nucleates and evolves in concordance with the pattern of the pre-existing domains.

In this paper, PZT piezoelectric ceramic specimens with 4 compositions (Zr/Ti=50/50, 53/47, 56/44, 58/42) in Pb(Zr,Ti)O3 system were fabricated. We studied effects of poling strength and thermal aging on the temperature characteristics of eletromechanical coupling factor k31 of the specimens, which were poled with the DC electric fields, 1.5, 2.5 and 3.5 kV/mm respectively and thermally aged for an hour at 200℃. The eletromechanical coupling factor k31 of the specimen with the composition Zr/Ti=53/47, nearest to the morphotropic phase boundary decreased the most greatly, irrelevant to the intensity of poling field, due to 1st thermal aging. And the temperature coefficient of eletromechaical coupling factor k31 was(-) in the ereragonal phase composition and (+) in the rhombohedral phase composition, which is reverse in the temperature coefficient of resonance frequency. It is interesting that eletromechanical coupling factor k31 of PZT ceramics is shown to be able to be able to increase as temperature increase in the interval -20~80℃.

Abstract: Carbon nanotubes (CNT) / polyvinylidene fluoride (PVDF) piezoelectric composite films for nanogenerator devices were fabricated by spray coating method. When the CNT/PVDF mixture solution passes through the spray nozzle with small diameter by the compressed nitrogen gas, electric charges are generated in the liquid by a triboelectric effect. Then randomly distributed {3 phase PVDF film could be re-oriented by the electric field resulting from the accumulated electrical charges, and might be resulted in extremely one-directionally aligned 13 phase PVDF film without additional electric field for poling. X-ray diffraction patterns were used to investigate crystal structure of the CNT/PVDF composite films. It was confirmed that they revealed extremely large portion of the f3 phase PVDF crystalline in the film. Therefore we could obtain the poled CNT/PVDF piezoelectric composite films by the spray coating method without additional poling process.