Ferroelectric Composites Research Articles

The phase transition and enhanced dielectric properties in La0.7Ba0.3MnO3 /P(VDF-HFP) composited films

Polymer-based ferroelectric composites, particularly those containing Poly (vinylidene fluoride) (PVDF), have emerged as preferred materials for flexible electronics and sensors owing to their excellent electro-mechanical attributes and ease of fabrication. The efficacy of PVDF composites is significantly influenced by the fillers and the proportion of the β-phase present. This research details the synthesis of La0.7Ba0.3MnO3 (LBMO) particles via solid-state reaction, surface-functionalized with acetic acid, and subsequently introduced as nucleating agents into Poly (vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) to fabricate LBMO/P(VDF-HFP) composite membranes. The LBMO fillers before modification significantly increased the β-phase content from 32.7 % to 87.8 % in 5 wt% unmodified LBMO/P(VDF-HFP) membranes. After modification, the hydroxyl groups attached to acetic acid-modified LBMO form hydrogen bonds with -CF2 groups in P(VDF-HFP), inducing the formation of the β phase while enhancing macroscopic polarization and piezoelectricity. At a 7.5 wt% acetate-modified LBMO doping level, the composite membrane exhibits a β-phase content of 64.5 %, but concurrently enhancing the film's dielectric properties. At 103 Hz, the dielectric constant of 5 wt% modified LBMO/P(VDF-HFP) membrane increases to 24.8, with a minimal rise in dielectric loss from 0.0293 to 0.0314. Moreover, under a 10 N compressive load at 1 Hz, the 5 wt% modified LBMO/P(VDF-HFP) composite achieves an open-circuit voltage of 4.3 V. These improved dielectric and piezoelectric properties indicate the composite's suitability for energy harvesting applications.

Relaxor-like behavior of the dielectric response of dense ferroelectric composites

We study experimentally and theoretically the influence of size effects and structural factors on the dielectric and ferroelectric properties of the dense ferroelectric composites. The composites have the form of the tape-casted films with 28 vol% of nanosized or submicron BaTiO3 particles dispersed in the polyvinyl butyral. We measured and analyzed the temperature dependences of the capacitance and dielectric losses in the temperature range (−200 – +200)oC and frequency range (102–105) Hz. The nonmonotonic temperature dependences of dielectric permittivity of the studied composite films have a wide plateau-like maxima located between 80oС and 160oС, in contrast to the relatively sharp maximum near the Curie temperature (∼124oC) observed in the fine-grained and coarse-grained ceramics, sintered from the same nanosized or submicron BaTiO3 particles at 1250oC. The shift of the dielectric permittivity and losses maxima (in more than 40oC) and their strong frequency dispersion do not agree with the behavior expected for the systems with a weak interaction between ferroelectric particles and a polymeric matrix. In contrast, we reveal the relaxor-like behavior of the composite dielectric response. To explain the observed results, we propose the analytical model, which considers the strong dipole-dipole cross-interaction of the BaTiO3 particles in the dense nanocomposite. The analytical model is corroborated by the structural studies of the BaTiO3 nanosized and submicron particles by X-ray phase analysis and static 137Ba NMR spectra, as well as by the finite element modelling of the composite polar properties, which confirms the strong cross-interactions between the dipole moments of single-domain nanoparticles and/or between the domain walls of different submicron polydomain particles.The obtained results may be useful for development of cheap and flexible lead-free dense ferroelectric nanocomposites with relaxor-like behavior of the dielectric response, which are promising for non-volatile memory and energy-saving elements, modulators, electrical converters and piezoresistive elements.

(Invited) Scalable Manufacturing and Application of Piezoelectric Biomaterials

Piezoelectric materials are a group of important functional building blocks that interfacing the human body by coupling biomechanical energy and electricity. So far, many technology innovations have advanced piezoelectric materials and composites toward a broad range of biomedical applications, which possess unique biocompatibility and flexibility. Fundamentally, materials design and engineering draw the boundary where this technology may advance. In this talk, I introduce our most recent development of piezoelectric materials and composites that are particularly designed for implantable nanogenerator applications. First, I present our wafer-scale approach to creating piezoelectric biomaterial thin films based on amino acids. The self-assembled sandwich film and truss-like structures enabled both strong piezoelectricity and largely improved flexibility. Then, new ferroelectric composites are presented as a new material used in 3D printing for directly manufacturing of piezoelectric architectures with tunable piezoelectric and mechanical properties. Toward the end, novel applications of implantable piezoelectric materials are introduced, which enable the closed-loop electrostimulations for many biomedical therapeutics.

Polysilane–Barium Titanate Polymeric Composite Obtained through Ultrasonication

This work describes the synthesis of a polysilane (PSH)–barium titanate (BT) ferroelectric polymer composite that keeps stable in the presence of ultraviolet light (UV). To evaluate the stability in the presence of UV radiation and the mechanism of interaction between the PSH matrix and BT, FTIR measurements were carried out. The UV/VIS absorption measurement reveals that PSH absorbs strongly in the ultraviolet range, while the composite behaves similarly to BT. Although PSH is a semiconductor, the dielectric spectrometry analysis determined that BT is a ferroelectric material due to its high dielectric constant and low dielectric losses. In contrast to the polymer matrix, the composite polymer has a greater dielectric constant and a lower loss permittivity. PSH is a semiconductor, as indicated by its electrical conductivity of 10−5 S/cm; nevertheless, the UV-irradiated polymer has antistatic properties (10−8 S/cm). Irradiated or not, the polymer composite is a semiconductor, with conductivity of 10−6 S/cm, significantly lower than that of PSH. The interaction with electromagnetic radiation indicates electromagnetic shielding behavior for both BT (highest absorption magnitude of −57 dB) and the polymer composite (maximum absorption magnitudes range from 8.4 to −15.2 dB). Based on these research results, the novel composite with specific characteristics may be used in electronic applications in UV-irradiated conditions.

Electronic cooling and energy harvesting using ferroelectric polymer composites

Thermal management emerges as a grand challenge of next-generation electronics. Efforts to develop compact, solid-state cooling devices have led to the exploration of the electrocaloric effect of ferroelectric polymers. Despite recent advances, the applications of electrocaloric polymers on electronics operating at elevated temperatures remain essentially unexplored. Here, we report that the ferroelectric polymer composite composed of highly-polarized barium strontium titanate nanofibers and electron-accepting [6,6] phenyl-C61-butyric acid methyl ester retains fast electrocaloric responses and stable cyclability at elevated temperatures. We demonstrate the effectiveness of electrocaloric cooling in a polymer composite for a pyroelectric energy harvesting device. The device utilizes a simulated central processing unit (CPU) as the heat source. Our results show that the device remains operational even when the CPU is overheated. Furthermore, we show that the composite functions simultaneously as a pyroelectric energy converter to harvest thermal energy from an overheated chip into electricity in the electrocaloric process. This work suggests a distinct approach for overheating protection and recycling waste heat of microelectronics.

Harnessing the Power of Nano‐Ferroelectrics: BaTiO3/MXene (Ti3C2Tx) Composites for Enhanced Lithium Storage

Abstract2D Ti3C2Tx MXene is a desirable electrode material for advanced lithium‐ion batteries (LIBs) in the pursuit of high energy and power densities, owing to its extensive reactive area and surface‐induced pseudo‐capacitance. Here, a novel synergistic strategy for fortifying lithium storage capability is first proposed, by in‐situ anchoring BaTiO3 ferroelectric nanoparticles on few‐layered Ti3C2Tx nanosheets (BT/f‐Ti3C2Tx) using a hydrothermal method. The uniform BaTiO3 nanoparticles effectively prevent the restacking of Ti3C2Tx nanosheets, successfully deplete metastable Ti atoms, and intriguingly form a thin and well‐adhered solid electrolyte interface layer, enhancing the aggregation‐resistant, oxidation‐resistant, and electrochemical properties of Ti3C2Tx. Simultaneously, the internal electric fields, originating from the spontaneous polarization of BaTiO3 ferroelectric nanoparticles, can augment the adsorption of Li+, boosting the lithium storage capacity and reaction kinetics. The resulting composite electrode displays a remarkable charge capacity of 84 mAh g−1 at 10 A g−1, almost five times that of pristine Ti3C2Tx electrode. The excellent rate performance and cyclability make BT/f‐Ti3C2Tx composites highly attractive for LIBs. Furthermore, this synthetic approach presented here is scalable and can be extended to other Ti‐based materials. This strategy is expected to underscore the considerable potential of ferroelectric composites for integration into high‐performance LIBs.

Ultrahigh efficiency and energy density in tri-layered ferroelectric polymer composites utilizing ultralow loading of micro-sized plates

Ferroelectric-based composites have demonstrated tremendous potential in electrostatic capacitor owing to their exceptional dielectric characteristics. However, it is extremely challenging to attain desirable energy density (Ue) and above 95% efficiency (η) under low electric fields in the ferroelectric polymer-based composites because of the dominating electrical conduction loss. Herein, ferroelectric polymer composites consisting of SrTiO3@SiO2 plates/(PVDF-co-HFP) as the inner layer and polycarbonate (PC) as the outer polymer layers are elaborately proposed. The vital role of the multiple interlaminar interfaces (electrode/dielectric interface and interlayer interface) on the reduction of conduction loss and improvement of corresponding energy storage properties of the ferroelectric polymer is verified by experimental and theoretical simulations. The resulting composite with an ultralow loading of SrTiO3@SiO2 plates (0.5 vol%) displays a record high capacitive performance (∼8.73 J/cm3) at above 95% η under the low electric field of 280 MV/m1, indicating an enormous ∼118% increment of the maximal Ue over the commercial bench-mark biaxially oriented polypropylene (∼4 J/cm3) and far outperforming those of the polymer-based dielectrics reported to date. Along with fast discharge time (9 ns), this contribution presents a versatile and competitive technology for fabricating composites with exceptional energy storage capabilities operating under low electric fields.

Highly luminescent, fast switching electro-optical device based on core-shell bimetallic nanoparticles/ ferroelectric liquid crystal composites.

Owing to the passive nature of liquid crystal (LC) materials, achieving luminous displays using pure LC materials is challenging. In addition, it is difficult to achieve a fast switching time using pristine ferroelectric LC devices without compromising their cell thickness. Herein, we have developed a fast switching and highly luminescent electro-optical device by dispersing a minute concentration of bimetallic nanoparticles (Au@Ag NPs) having a spherical gold core and a silver shell within a ferroelectric liquid crystal (FLC) host matrix, ZLI3654. Au@Ag core-shell NPs having synergic attributes of both counterparts were successfully synthesized by a facile seed-mediated route. The Au core helps to tune the shape of the Ag shell and provides enhanced electron density as well as improved stability against oxidation. Introducing nanoparticles induces little structural modifications to the host FLC, resulting in an improvement in the mesogenic alignment. Interestingly, ∼29-fold enhancement in the photoluminescence (PL) intensity is observed on dispersing 0.25 wt% of Au@Ag NPs into the FLC host matrix. The enhanced electromagnetic field in the FLC-nanocomposite is attributed to the Localized Surface Plasmon Resonance of Au@Ag NPs, which strengthens the photon absorption rates by the FLC molecules, culminating in the massive enrichment of the PL intensity. In addition, the improved localized electric field inside the FLC device led to a noticeable enhancement in the spontaneous polarization, dielectric permittivity, and, most interestingly, ∼53% fastening in the switching time at an optimum concentration (0.25 wt%) of Au@Ag NPs. The improved electro-optical parameters of the Au@Ag NPs/FLC composite have been compared with the performance of both pristine Au NPs/FLC and Ag NPs/FLC composites, respectively, for the comprehensiveness of the study. The present study paves a systematic way to develop FLC-based advanced electro-optical devices with faster switching and higher luminescence properties.

Wearable self-powered ballistic signal detectors with ferroelectric composites arrays for cardiovascular and diabetic complication

Abstract Background Flexible and wearable electronic devices with lightweight are needed to monitor and guide treatment in patients with cardiovascular disease and diabetic complication. We aimed to develop self-powered wearable bio-signal sensing arrays for cardiovascular and diabetic complication diagnosis and continuous monitoring. Methods Ferroelectric composites were designed to have piezoelectric property and high flexibility. Detection of arterial pulse as ballistogram (BCG) was simultaneously compared with electrocardiogram (ECG) in 20 controls. Heart rate and components of ECG was compared with those of BCG. Then, 9 ferroelectric BCG sensors as a square type array with self-power generation were fabricated to attachable thin film. Pressure distribution with BCG sensor array attached to socks were compared between 20 controls and 20 patients with diabetic neuropathy or vasculopathy during standing and ambulation for gait pressure distribution. Pressure distribution pattern was compared to neuropathy and vasculopathy parameters. Results Heart rate between BCG and ECG was significantly correlated (interclass correlation coefficient, ICC 0.99, 95% CI 0.98-0.99, p<0.001). QRS and T wave in ECG were correlated to second and third wave in BCG. Radial artery augmentation index by blood pressure monitoring was significantly correlated to BCG pressure (ICC 0.76, 95% CI 0.38-0.90, p=0.002). Analysis of foot pressure distribution demonstrated the highest pressure point at the anterolateral plantar area below a little tow. However, pressure gradient between anterolateral and anteromedial plantar area in diabetic patients was greater than that in controls (42.3±10.2 mV vs. 31.2±8.5 mV, p=0.024). Pressure gradient in diabetic patients was correlated to ankle-brachial index (ICC 0.62, 95% CI 0.32-0.90, p=0.036), but not to neuropathy parameters. Conclusion Wearable BCG sensor could accurately detect heart rate, blood pressure index and significantly correlated to ABI. Pressure distribution pattern and gradient analysis in diabetic patients by wearable BCG sensor arrays might predict diabetic complications. Gait remedial training guided by wearable BCG sensor arrays might aid to prevent diabetic complications.

Ferroelectric Composites of BaTiO3 and SrTiO3 with the Low-Melting Additive B2O3

Ferroelectric Composites of BaTiO3 and SrTiO3 with the Low-Melting Additive B2O3

Perovskite solar cells with ferroelectricity

AbstractHalide perovskites show excellent optoelectronic properties for solar cell application. Notably, perovskite crystalline structures have been widely reported to deliver superior ferroelectric properties. As a result, the integration of the ferroelectric process with the photon‐to‐electron energy conversion process becomes feasible to generate interesting photo‐physical properties and further boost the device performance of perovskite solar cells (PSCs), which have started to attract more and more attention in recent years. Here, we have reviewed the recent progress in PSCs with ferroelectricity (FE‐PSCs), by classifying them into three regimes according to the degree of phase segregation, for example, the layer‐structured ferroelectric/halide perovskite composite, micro phase‐separated ferroelectric/halide perovskite composite, and the intrinsic ferroelectric halide perovskite composite. The different composite structures enable a large range of interesting optoelectronic properties and the specific structure significantly enhances the device performance of PSCs. The most prominent contribution of ferroelectricity is that it can provide an extra electrical field to drive charge generation, transport, and collection. Further, key challenges and opportunities of the integration of ferroelectricity with photovoltaics are discussed. We hope our work can draw intensive attention in this field to accelerate the establishment of the basic theories in ferroelectricity and the commercialization of PSCs.

Improved Energy Storage Performance of Composite Films Based on Linear/Ferroelectric Polarization Characteristics.

The development and integration of high-performance electronic devices are critical in advancing energy storage with dielectric capacitors. Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (PVTC), as an energy storage polymer, exhibits high-intensity polarization in low electric strength fields. However, a hysteresis effect can result in significant residual polarization, leading to a severe energy loss, which impacts the resultant energy storage density and charge/discharge efficiency. In order to modify the polarization properties of the polymer, a biaxially oriented polypropylene (BOPP) film with linear characteristics has been selected as an insulating layer and combined with the PVTC ferroelectric polarization layer to construct PVTC/BOPP bilayer films. The hetero-structure and polarization characteristics of the bilayer film have been systematically studied. Adjusting the BOPP volume content to 67% resulted in a discharge energy density of 10.1 J/cm3 and an energy storage efficiency of 80.9%. The results of this study have established the mechanism for a composite structure regulation of macroscopic energy storage performance. These findings can provide a basis for the effective application of ferroelectric polymer-based composites in dielectric energy storage.

From Swiss-cheese to discrete ferroelectric composites: assessing the ferroelectric butterfly shape in polarization loops

We explore the polarization hysteretic behaviour and field-dependent permittivity of ferroelectric-dielectric 2D materials formed by random dispersions of low permittivity inclusions in a ferroelectric matrix, using finite element simulations. We show how the degree of impenetrability of dielectric inclusions plays a substantial role in controlling the coercive field, remnant and saturation polarizations of the homogenized materials. The results highlight the significance of the degree of impenetrability of inclusion in tuning the effective polarization properties of such ferroelectric composites: coercive field drops significantly as percolation threshold is attained and remnant polarization decreases faster than a linear decay.

Ferroelectric Thin Films and Composites Based on Polyvinylidene Fluoride and Graphene Layers: Molecular Dynamics Study

This work is devoted to the study of nanosized polymer polyvinylidene fluoride (PVDF) thin ferroelectric films (two-dimensional ferroelectrics) and their composites with graphene layers, using molecular dynamics methods to (1) study and calculate the polarization switching time depending on the electric field and film thickness, (2) study and calculate the polarization switching time depending on changes of the PVDF in PVDF-TrFE film, and (3) study the polarization switching time in PVDF under the influence of graphene layers. All calculations at each MD run step were carried out using the semi-empirical quantum method PM3. A comparison and analysis of the results of these calculations and the kinetics of polarization switching within the framework of the Landau–Ginzburg–Devonshire theory for homogeneous switching in ferroelectric polymer films is carried out. The study of the composite heterostructures of the “graphene-PVDF” type, and calculations of their polarization switching times, are presented. It is shown that replacing PVDF with PVDF-TrFE significantly changes the polarization switching times in these thin polymer films, and that introducing various graphene layers into the PVDF layered structure leads to both an increase and a decrease in the polarization switching time. It is shown that everything here depends on the position and displacement of the coercive field depending on the damping parameters of the system. These phenomena are very important for various ferroelectric coatings.

Influence of ultrasonic treatment and heating/cooling under electric field on high-k cellulose-barium titanate composites

The present research reports the ultrasonic assisted synthesis of ferroelectric cellulose-barium titanate composites (C/BT). As proved by wide angle X-ray diffraction (WAXD) and by scanning electronic microscopy (SEM), the composites consist of perovskite-type barium titanate particles (BT) of 400- 600 nm, disposed around the cellulose microfibers. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and wide angle X-ray diffraction (WAXD) revealed the modifications of structure/morphologies of the prepared sample as compared to pristine cellulose, with direct consequences on the polymer crystalline domains, on the uniformity of BT dispersion and on the dielectric properties of the composites. The composites obtained by ultrasonic treatment possess high dielectric constants (58.6-140.5), better breakdown strengths (8.9-17.7 kV/mm) and energy storage densities (2.6-9.0 J/cm3) as compared to BT particles, as well as very low dielectric losses (0.27-3 x 10-4) at industrial frequencies (50-55 Hz), the values being dependent on the content of barium titanate and on the preparation parameters.

Properties of ferroelectric composites in the microwave range

Ferroelectric ceramics of barium titanate and its solid solutions have found wide applications in technology, while compositions of a binary system with strontium titanate are most in demand. Electrically controlled components based on the barium titanate – strontium titanate ferroelectric ceramics are widely used in accelerator technology and the use of these materials is relevant at the present time. In the microwave range, composites based on the solid solution system barium titanate – strontium titanate ВаxSr1–xTiO3 (BST). Ferroelectric samples based on ВаxSrx–1TiO3 compound, where x = 0; 0.1; 0.3; 0.5; 0.7 were obtained using a conventional ceramic technology. The temperature dependences of the electrical properties of bulk ceramic samples based on ferroelectric composites were received in the temperature range 100°C to 350°C at a frequency of 1 kHz. It has been established that dielectric parameters significantly depend on the BaTiO3 content in BST compositions. To carry out a research in the frequency range from 0.1 to 8.5 GHz, an experimental setup was manufactured for measuring the electrical properties of ferroelectric materials based on an Agilent E5071C vector analyzer and a microstrip line. To conduct temperature studies, a microstrip line with a controlled sample was placed in a heat, cold and moisture chamber of the Bench-Top SU-261 series, in which it has been heated up to 60°C. The amplitude-frequency characteristics of the transmission coefficient (S21) of samples when heated from 20 °C to 60°C with an interval of 10 degrees were studied. The resonant frequency and quality factor of the resonator have been determined from the amplitude-frequency characteristic. Based on the value of the resonant frequency and the geometric dimensions of the sample, the dielectric constant of the sample material was calculated. It has been shown that with increasing barium titanate content (x = 0.1–0.3), the dielectric constant of the samples under study increases, and the resonant frequency shifts to lower frequencies. For samples with a barium titanate content of 50% and higher (x≥0.5), there are no resonance dependences and strong absorption of electromagnetic waves is observed. It has been established that with increasing temperature, the resonant frequency of composite material samples shifts to higher frequencies. Frequency dispersion of the dielectric constant is observed, which indicates the relaxor properties of the ceramic samples under study. Experimental investigations were carried out using a microwave strip line, a coaxial measuring cell and a capacitive converter; this made it possible to measure the dielectric constant of materials with values of more than several hundred in the microwave range and significantly reduce the control time when conducting thermal studies. It was shown that with a change in temperature, the electrophysical properties of the samples change significantly, which can be used in various systems and devices to change the reflection coefficient and phase of the electromagnetic wave.

Observation of the local electromechanical response in 2–2 ceramic–ceramic lead-free ferroelectric composites via digital image correlation

This study investigates bilayers of 0.94(Na1/2Bi1/2)TiO3–0.06BaTiO3 (NBT–6BT) and 0.90(Na1/2Bi1/2)TiO3–0.06BaTiO3–0.04(K0.5Na0.5)NbO3 (NBT–6BT–4KNN) using digital image correlation, enabling the separate analysis of strain response in each layer. The bilayers were electrically connected without mechanical connection (polarization coupled) as well as mechanically and electrically connected (polarization and strain coupled) to determine the role of interlayer mechanical interactions. The large signal longitudinal and transverse piezoelectric coefficients, d33∗ and d31∗, were characterized for both cases. In the polarization coupled composite, d33∗ decreased linearly from 410 to 260 pm/V with increasing vol. % NBT–6BT. In contrast, in the polarization and strain coupled case, d33∗ and d31∗ were maximum at 50 vol. % NBT–6BT with values of 440 and −130 pm/V, respectively, highlighting the critical role of strain interactions in ceramic–ceramic composites. The stress-induced phase transformation through strain coupling significantly impacted the electromechanical response, with improved strain values observed in the NBT–6BT–4KNN layer. Furthermore, this study highlights the variability in the significance of strain coupling within bilayer systems as a function of the altering volume fraction of their constituent components.

Biowaste-based porous carbon nanoparticle doped polymer dispersed ferroelectric liquid crystal composites: an impact on optical and electrical properties

Bio-waste-based porous carbon nanoparticles (PCNPs) were synthesized using green synthesis and investigated their doping effect on the optical and electrical properties of polymer-dispersed ferroelectric liquid crystals (PDFLCs) composites. Here we employed the polymerization-induced phase separation (PIPS) approach for constructing the PDFLCs. Our results indicate that the dispersion of PCNPs into the PDFLC material results in an alteration to several physical parameters, including morphology, dielectric permittivity, conductivity and optical band gap. A decrease in the ac conductivity of the doped samples was seen. Additionally, UV-Visible study reveals that inclusion of PCNPs resulted in a decrease in the optical band gap of PDFLC, with a value of approximately 3.1 eV. These findings demonstrate the potential of using PCNPs as dopants in PDFLCs for various applications, including sensing, energy storage and optoelectronics.

Tri-layer high-temperature all-organic films with superior energy-storage density and thermal stability

Tri-layered all-organic composites exceed the upper energy-storage-density limits of commercial bench-mark BOPP (∼1.4 J cm−3) and representative ferroelectric polymer-based composites (<4 J cm−3) at elevated temperature.

A wireless ultrasound energy harvester based on flexible relaxor ferroelectric crystal composite arrays for implanted bio-electronics

We proposed a bio-inspired PUEH based on high-performance relaxor ferroelectric crystal composites. The as-developed PUEH exhibited a high output power density of 0.27 mW mm−3, surpassing those of reported PUEHs.