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To enhance the piezoelectric properties of poly (vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE))-based composites and prepare a piezoelectric sensor with high sensitivity, two types of potassium sodium niobate (KNN) fillers, micro-particles (MPs) and micro-rods (MRs), were individually doped into a P(VDF-TrFE) matrix to form composites using a traditional solution-casting process. Identically, the two groups of P(VDF-TrFE)-based piezoelectric composites doped with KNN MPs and KNN MRs exhibited an enhanced β -phase and typical ferroelectricity with high residual polarization (P r), which resulted in good piezoelectric constant (d 33) and sensing electrical response. In contrast, the KNN MRs/P(VDF-TrFE) composite showed better piezoelectric output performance compared to the KNN MPs/P(VDF-TrFE) composite in all test scenarios, which is attributed to its depressed dielectric permittivity owing to the ameliorative conductivity dielectric loss. An output voltage (U) of 16 V, 4 V, and 6 V were recorded using 10 g zirconium ball impacting, finger tapping, and finger bending, respectively, in the KNN MRs/P(VDF-TrFE) sensors. This research demonstrates the impact of the filler shape on the electrical performance of P(VDF-TrFE)-based piezoelectric composites, which provides a reliable reference to enhance the energy harvesting and conversion performance of self-powered electronic devices. [ABSTRACT FROM AUTHOR]

A group of 1–3 type piezoelectric Pb (Mg 1/3 Nb 2/3)O 3 -PbTiO 3 /polyvinylidene fluoride (PMN-PT/PVDF) composite sheets are prepared using a complex two-step hot-pressing method. Then the molecular structure model of piezoelectric materials and an inverse piezoelectric simulation of the composites are performed to express the horizontal compression, indicating the clamping activity of ferroelectric PVDF on PMN-PT. As such, this composite sheet possesses a high dielectric permittivity (ε r) of 560 at 100 Hz for its compacted connecting of two phases. After polarization, a very large piezoelectric coefficient (d 33) of 1125 pC/N and a considerable electromechanical coupling factor (k t) of 0.43 is obtained in PMN-PT/PVDF sheet with a proper aspect ratio of 1.4 and a thickness of 2.1 mm, further indicating that promoting effect of PVDF matrix on the strain in Z-direction of PMN-PT. The result shows that ferroelectric PVDF serving as polymer matrix favors the electromechanical coupling effect, and may provide a prospect of the potential application of PMN-PT/PVDF composite in sensor or transistor for matrix ultrasonic probes. [ABSTRACT FROM AUTHOR]

The perfluoroalkyl ethylene ether (PMVE), perfluoro propoxyethylene (PPVE), and chlorofluoroethylene (CFE) (<4 mol%) as the third monomers are embed into the ferroelectric polyvinylidene-trifluoroethylene (P(VDF-TrFE)), respectively, aiming to modify the ferroelectric behaviors of the copolymers. Through calculation, we find the PPVE and PMVE molecular segments possess a large free volume but a low polarity, effective promoting the formation of all-trans β phase in the crystal region of P(VDF-TrFE), and contributing to the high maximum and remnant polarization (P s and P r) of related P(VDF-TrFE-PPVE) (∼6.8 and 6.3 μC cm−2) and P(VDF-TrFE-PMVE) (∼5.6 and 5.0 μC cm−2) under 200 MV m−1, respectively. Differently, the CFE segment provides not only a large volume but also a high polarity, resulting in the phase transition from β to α and thus, the target terpolymer P(VDF-TrFE-CFE) appears a transition from ferroelectrics to relaxor ferroelectrics, and shows a high dielectric permittivity (ε r ∼55.4) at 100Hz. This work may provide a comprehensive insight of modifying the structures of P(VDF-TrFE), offering crucial guidance for optimizing the design of this type ferroelectric materials. [Display omitted] • PMVE, PPVE, and CFE as the third monomers are respectively embed into P(VDF-TrFE) to fabricate its ferroelectric behavior. • CFE provides a large volume and a high polarity, resulting in a phase transition from ferroelectrics to relaxor ferroelectrics. • PPVE and PMVE possess a large free volume but a low polarity, only effective promoting the ferroelectric β phase. [ABSTRACT FROM AUTHOR]

The electromechanical properties of PVDF-based polymers, namely converting electrical into mechanical energy, are mainly decided by the crystal structure and domain size of the target product. Thus, we prepare the poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)), its terpolymer poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)), and tetrapolymer poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene -hexafluoropropylene) (P(VDF-TrFE-CFE-HFP)) films for comparison, respectively, where the role of the introduction of third and fourth monomers in the electromechanical properties of P(VDF-TrFE) is completely disclosed. Because of introducing CFE and HFP monomers, P(VDF-TrFE) with the ferroelectricity has converted into the relaxor ferroelectric P(VDF-TrFE-CFE-HFP) with a slimmer P-E loop while maintaining good maximum polarization (P m). Since the nano ferroelectric domains in the relaxor ferroelectric material are easy to reverse along the polarizing electric field, The P(VDF-TrFE-CFE-HFP) sample achieved a dielectric constant (ε r) of ∼29 and a strain in the thickness direction (S 33) of ∼ -5%, respectively, while the ε r and S 33 of P(VDF-TrFE) sample are ∼11 and ∼-0.8 %, respectively. This research indicates the availability of the third and fourth monomers for improving the electromechanical effect of such electrostrictive polymers, having wide applications in flexible actuators, transformers, sensors, and so forth. In this work, we developed a P(VDF-TrFE-CFE-HFP) tetrapolymer by introducing a small amount of hexafluoropropylene (HFP) into P(VDF-TrFE-CFE). A high dielectric constant (ε r) of ∼29 and a strain in the thickness direction of ∼ -5% are obtained in the P(VDF-TrFE-CFE-HFP) sample, respectively, which is higher than that of the P(VDF-TrFE) sample (∼11 and ∼-0.8 %). [Display omitted] • P(VDF-TrFE-CFE-HFP) film sample was fabricated by the solution-casting method. • The HFP monomer could enable the polymer with the relaxor ferroelectricity to keep high maximum polarization. • A dielectric constant (ε r) of ∼29 and an electrostriction (S 33) of ∼-5% are obtained in P(VDF-TrFE-CFE-HFP). [ABSTRACT FROM AUTHOR]

Piezoelectric self-powered electronic devices can convert ambient mechanical vibrations into electrical energy in an environmentally friendly manner, significantly alleviating the scarcity of non-renewable sources. This work prepares an one-dimensional potassium sodium niobate micro rods (1D KNN MRs) using the molten salt - topological chemical reaction method, showing the significant advantages over 0-dimension (0D) nanoparticles due to its anisotropy. Simultaneously, KNN MRs are introduced into poly (vinylidene fluoride-trifluoroethylene) to form a KNN MRs/P(VDF-TrFE) piezoelectric composite, effectively facilitating the piezoelectric β -phase in P(VDF-TrFE) film, and contributing to a high remnant polarization (P r ∼12.3 μC/cm2) at 125 MV/m and a high piezoelectric constant (d 33 = −28 pC/N). Interestingly, a piezoelectric sensor assembled by KNN MRs/P(VDF-TrFE) composite shows a considerable piezoelectric output of 17.6 V at a scene of 2.5 MPa stress, offering a novel route for designing the optimum ceramic/polymer combinations suitable for mechanical energy conversion and energy harvesting. [Display omitted] [ABSTRACT FROM AUTHOR]

Nb5+ and Ga3+ co-doped Ti 0.9 Zr 0.1 O 2 ceramics were synthesized using the conventional solid-state reaction method. Single rutile-liked phase of octahedron structure were identified for all compositions in (Nb 0.5 Ga 0.5) x (Ti 0.9 Zr 0.1) 1-x O 2 (NGT) with x = 0.01 to 0.10 by X-ray diffraction patterns coupled with Rietveld refinement. Microstructural scanning image, together with energy dispersive x-ray spectroscopy (EDX), revealed good chemical homogeneity in NGT samples. A giant dielectric permittivity of 5 × 104 and a low loss of 0.02 was obtained in NGT with x = 0.01 due to the contribution of electron-pinned and defect-dipole effect. Furthermore, a temperature (-20–120 °C), frequency (0.1–104 Hz) and bias electric field (100–200 V/mm) independent dielectric permittivity and loss was found in this composition, which is critical for potential applications of supercapacitors. [ABSTRACT FROM AUTHOR]

Abstract An ultraviolet photosensitive ZrO 2 precursor solution was prepared using acetylacetone as the chelating agent and n-butanol zirconium (Zr(OC 4 H 9) 4) as the raw material. Sol-gel-derived ZrO 2 pore-sealing films were fabricated on a micro-arc oxidized aluminum alloy (MAO-Al). The coated ZrO 2 sol-gel films were treated by either UV irradiation or a heat treatment process. The corrosion properties of the ZrO 2 /MAO-Al materials in a 3.5 wt % NaCl solution were studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). X-ray diffraction (XRD) measurements showed that the ZrO 2 layer was amorphous. Scanning electron microscopy (SEM) results revealed that cracks could easily form in the ZrO 2 films that were heat treated at 100 °C and 300 °C, thus degrading the corrosion resistance of the samples. However, UV irradiation can help to prevent cracking. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) indicated that UV light decomposes the organic species in a ZrO 2 sol-gel film at low temperatures, facilitating the formation of a Zr-O-Zr network in the film. The anticorrosion ability of a sample with a ZrO 2 film irradiated by UV light at 100 °C is enhanced compared with those of samples coated by a ZrO 2 layer and heat treated at 100 °C or 300 °C. [ABSTRACT FROM AUTHOR]

Abstract: The dielectric, piezoelectric and ferroelectric properties of a poly (vinylidene fluoride-co-trifluoroethylene) (P (VDF-co-TrFE)) copolymer synthesized via a novel hydrogenation process are presented in this work. Comparing with the direct copolymerized P(VDF-co-TrFE), the head-to-head (H–H) connection of vinylidene fluoride (VDF) and trifluoroethylene (TrFE) units in hydrogenized P(VDF-co-TrFE) results in the increasing crystal domains and the improvement of overall crystallinity and. Therefore, excellent electric properties, including dielectric constant of 11 at a frequency of 100 Hz, a piezoelectric value (d 33) of −23 pC/N, a remnant polarization (P r ) of 7 μC/cm2 and a maximum polarization (P s ) of 10 μC/cm2 were observed in hydrogenized P(VDF-co-TrFE), which are rather close to that obtained in copolymerized copolymer. The results indicate that the improved condensed structures offer the low cost and convenient hydrogenized P(VDF-co-TrFE) broader application scenery in piezoelectric devices than the direct copolymer. [Copyright &y& Elsevier]

Abstract: A series of poly(vinylidene fluoride-chlorotrifluoroethylene) (P(VDF-CTFE))/barium strontium titanate (BST) nanocomposites were fabricated by solution casting method. The addition of BST nanoparticles could enhance both the dielectric constant and the displacement of the resultant composite significantly. The surface activation of BST nonaparticles with KH550 was confirmed as an effective way to improve the breakdown strength of the composite. The high electric displacement (D >15μC/cm2), breakdown field (>200MV/m) and low dielectric loss in P(VDF-CTFE)/BST nanocomposites suggest that the high electrical energy density may be desirable. That indicates the potential application of this class of copolymer/ceramics nanocomposites for high energy storage components. [Copyright &y& Elsevier]