Ferroelectric Matrix Research Articles

A study on BaTiO3 – NiFe2O4 composite; microstructure, multiferroic and magnetodielectric properties

The lead-free x NiFe2O4 – (1-x) BaTiO3 (x = 0, 0.05, 0.1, 0.15) multiferroic composites were prepared via the solid-state sintering technique. Microstructure, multiferroic, and magnetodielectric properties of composites were investigated. According to the XRD data (from x = 5 to 15 wt%), the tetragonality factor (cT/aT) and unit cell volume of the BaTiO3 (BTO) crystal system diminished. Based on SEM images, ferromagnetic NiFe2O4 (NFO) grains are uniformly dispersed in the ferroelectric BTO matrix without additional reaction in the interfaces of two phases. The highest values of dielectric (dielectric constant (εr) ∼ 1905 and dielectric loss factor (tan δ) ∼ 0.049) and ferroelectric properties (saturation polarization (PS) ∼ 13 μC/cm2 and remnant polarization (Pr) ∼ 10 μC/cm2) are attained for x = 5 wt% due to the lowest NFO (non-ferroelectric) concentration. Also, with increasing ferrite concentration (up to 15 wt%), the ferroelectric properties of the composites show a gradual decrease. The saturation magnetization (MS) values rise due to increasing ferrite concentration (from 2 to 5 emu/g for x = 5 to 15 wt%). Moreover, coercivity (HC) drops from 150 to 110 Oe. The simultaneous observation of the ferroelectric and ferromagnetic characteristic hysteresis loops confirmed the multiferroic effect for x = 5, 10, and 15 wt%. The highest magnetodielectric constant (3 %) is obtained for x = 15 wt% multiferroic composite at the applied magnetic field of 6 kOe.

An Intragranular Segregation Structure Enables an Excellent Energy Storage Performance in Composite Dielectrics through Delayed Saturation Polarization.

An electrostatic capacitor for energy storage is an important basic component of pulse power electronics. The electrical breakdown strength (Eb) of normal ferroelectrics is low, which limits their application in dielectric energy storage. Constructing a 0-3-type composite dielectric, that is, introducing an insulating metallic oxide into the ferroelectric matrix, can greatly enhance Eb. Unfortunately, an intergranular secondary phase typically forms that causes large attenuation of the dielectric constant, which leads to limited improvement of energy storage performance. In this work, a composite ceramic with an intragranular segregation structure was intentionally designed using the BaTiO3-BaZrO3-CaTiO3 (BCZT) system as an example. Compared with those of a BCZT solid solution without a secondary phase and a BCZT composite with a grain-boundary secondary phase, the rationally designed BCZT composite with an intragranular secondary phase delivered a large recoverable energy density of 5.86 J/cm3 and high efficiency of 86.7% at a moderate electric field of 550 kV/cm. Such performance was achieved because the intragranular segregation structure displayed delayed saturation polarization with a high Eb. This microstructural engineering strategy is generally applicable to optimize composite dielectrics to meet the demands of high-performance energy storage capacitors.

Ultrathin Ternary FeCoNi Alloy Nanoarrays in BaTiO3 Matrix for Room-Temperature Multiferroic and Hyperbolic Metamaterial.

Multifunctional vertically aligned nanocomposite (VAN) thin films exhibit considerable potential in diverse fields. Here, a BaTiO3-FeCoNi alloy (BTO-FCN) system featuring an ultrathin ternary FCN alloy nanopillar array embedded in the BTO matrix has been developed with tailorable nanopillar size and interpillar distance. The magnetic alloy nanopillars combined with a ferroelectric oxide matrix present intriguing multifunctionality and coupling properties. The room-temperature magnetic response proves the soft magnet nature of the BTO-FCN films with magnetic anisotropy has been demonstrated. Furthermore, the anisotropic nature of the dielectric-metal alloy VAN renders it an ideal candidate for hyperbolic metamaterial (HMM), and the epsilon-near-zero (ENZ) wavelength, where the real part of permittivity (ε') turns to negative, can be tailored from ∼700 nm to ∼1050 nm. Lastly, room-temperature multiferroicity has been demonstrated via interfacial coupling between the magnetic nanopillars and ferroelectric matrix.

Metadielectrics for high-temperature energy storage capacitors

Dielectric capacitors are highly desired for electronic systems owing to their high-power density and ultrafast charge/discharge capability. However, the current dielectric capacitors suffer severely from the thermal instabilities, with sharp deterioration of energy storage performance at elevated temperatures. Here, guided by phase-field simulations, we conceived and fabricated the self-assembled metadielectric nanostructure with HfO2 as second-phase in BaHf0.17Ti0.83O3 relaxor ferroelectric matrix. The metadielectric structure can not only effectively increase breakdown strength, but also broaden the working temperature to 400 oC due to the enhanced relaxation behavior and substantially reduced conduction loss. The energy storage density of the metadielectric film capacitors can achieve to 85 joules per cubic centimeter with energy efficiency exceeding 81% in the temperature range from 25 °C to 400 °C. This work shows the fabrication of capacitors with potential applications in high-temperature electric power systems and provides a strategy for designing advanced electrostatic capacitors through a metadielectric strategy.

The atomic configuration and metallic state of extrinsic defects in Nb-doped BiFeO3 thin films

Defects in ferroelectric materials can cause microscopic strain and electron doping, which opens up new possibilities for unique physical properties in nanoelectronics. However, comprehending the relationship between these deep-buried defect configurations and the resulting physical properties is a long-term challenge. Here, utilizing the integrated differential phase imaging technique equipped in scanning transmission electron microscopy combined with energy dispersive X-ray spectroscopy, we show the full element-resolved atomic configuration of characteristic extrinsic defects in Nb-doped epitaxial BiFeO3 thin films. Atomic-resolution characterization reveals that the Nb doping substitutes Fe at the center of an oxygen octahedron and creates Fe vacancies near the defect core, leading to the formation of one perovskite cell-wide BiNbO3 chain that is expanded by 19 % in perovskite cell volume and rotated by 45° relative to the matrix lattice. Further quantitative analysis of the defect demonstrates that the ferroelectric polarization distribution around the dopant-induced defects displays a “head-to-head” configuration, indicating the accumulation of negative charges. Supported by electron energy loss spectroscopy and density functional theory calculations, the linear defect leads to one-dimensional metallic channels embedded within the ferroelectric BiFeO3 matrix. These atomic-scale findings establish the structure-functionality relationship of extrinsic defect in Nb-doped BiFeO3 thin films, providing new insight into their fundamental understanding and potential use in low-dimensional nanoelectronics devices.

Strong Local Polarization Fluctuations Enabled High Electrostatic Energy Storage in Pb-Free Relaxors.

Electrostatic energy-storage ceramic capacitors are essential components of modern electrified power systems. However, improving their energy-storage density while maintaining high efficiency to facilitate cutting-edge miniaturized and integrated applications remains an ongoing challenge. Herein, we report a record-high energy-storage density of 20.3 J cm-3 together with a high efficiency of 89.3% achieved by constructing a relaxor ferroelectric state with strongly enhanced local polarization fluctuations. This is realized by incorporating highly polarizable, heterovalent, and large-sized Zn and Nb ions into a Bi0.5Na0.5TiO3-BaTiO3 ferroelectric matrix with very strong tetragonal distortion. Element-specific local structure analysis revealed that the foreign ions strengthen the magnitude of the unit-cell polarization vectors while simultaneously reducing their orientation anisotropy and forming strong fluctuations in both magnitude and orientation within 1-3 nm polar clusters. This leads to a particularly high polarization variation (ΔP) of 72 μC cm-2, low hysteresis, and a high effective polarization coefficient at a high breakdown strength of 80 kV mm-1. This work has surpassed the current energy density limit of 20 J cm-3 in bulk Pb-free ceramics and has demonstrated that controlling the local structure via the chemical composition design can open up new possibilities for exploring relaxors with high energy-storage performance.

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.

The enhanced ionic thermal potential by a polarized electrospun membrane.

Inspired by thermally sensitive ion channels in human skin, a polarized membrane composed of a ferroelectric polymer fiber matrix is used to double the heat-induced potential in ionic thermoelectric devices. The comparison of the thermal potentials between different directions of polarization and temperature gradient indicates the importance of cation-dipole interactions for the enhancement.

Analysis of the electromagnetic properties of 2000NN/2000NM composites with ferroelectric and polymer matrices

The results of studying the electrical properties of ferrite-dielectric composites containing inclusions of Mn-Zn and Ni-Zn spinel ferrites with the same initial magnetic permeability (grades 2000NM and 2000NN, respectively) and different electrical resistance are presented. Four matrix materials, polymer and ceramic dielectrics with a different dielectric permittivity were used in the experiments: polystyrene (PS525), polyvinylidene fluoride (grade F2MB), lead zirconate titanate (ZTS-21), and barium titanate (TBK-3). Experimental samples of composites were obtained by hot (for a polymer matrix) or cold pressing with a binder (in case of ferroelectric ceramic matrix). It has been shown that the microwave-absorbing properties of the resulting composites significantly depend on the electrical properties of the dielectric matrix and the electrical resistivity of the filler. The highest attenuation of electromagnetic waves of 25 – 27 dB in the frequency range 4 – 5 GHz is observed for ferrite-polymer composites with a semiconductor filler of 2000NM with a thickness of microwave-absorbing material of 6 mm. For composites with Mn-Zn ferrite filler, a pronounced shift in the dispersion region of magnetic permeability is also observed, which in turn changes the frequency position of peak radio absorption. For the composites with a ferroelectric matrix, the operating frequency range for both fillers shifted to the low-frequency region 1 – 4 GHz with a maximum attenuation of up to 22 dB at the same thickness. It was experimentally confirmed that at a concentration of ferrite Cm = 40 % wt., the value of the frequency of absorption peal center fc and the minimum value of the reflection loss Kref for a filler with high electrical resistance of 2000NN decrease with an increase in the dielectric constant of the matrix. As for the composites with a 2000NM filler, the (ε’ of the matrix) dependence passes through a minimum. The obtained composites can be considered as effective microwave-absorbing materials for the frequency range 1 – 6 GHz with peak attenuation of the electromagnetic wave in the range 14 – 27 dB and frequency band (less than 10 dB) in the range 1.1 – 2.5 GHz.

Negative differential resistors from carbon-based cryogels incorporating graphene oxide into a ferroelectric polymer matrix

Electronic components with negative differential resistance (NDR) are essential in power electronics to build Gunn diodes, varactors, parametric amplifiers and switching circuits. However, their implementation through silicon-based electronics is costly and demands complex circuitry and components. Here, we introduce for the first time a class of hybrid carbon-based and organic aerogels, prepared at liquid nitrogen temperature (77 K) by a simple and scalable freeze-drying method. These cryogels exhibit NDR. In these cryogels, the carbonaceous phase is represented by d-glucose-graphene oxide nanocomposites while the organic phase is represented by polyvinylidene difluoride (PVDF), a ferroelectric polymer. NDR in our samples is assigned to the local electric field effects of PVDF on the charge carriers of more electrically conducting graphene oxide and d-glucose. Through an operando study via scanning near-field optical microscopy, we also show that low thermal expansion and low thermal conductivity are essential to prevent undesired effects in our devices through parasitic capacitance's discharge.

Magnetoelectric properties of multiferroic ceramic composites

The paper analyzes the influence of hard and soft admixture on the functional properties of multiferroic ceramic composites. Two composite materials via solid-state reaction route were obtained. PZT-type materials (with hard or soft admixture) were selected as the ferroelectric component (90%), and nickel–zinc ferrite as the magnetic component (10%). The influence of the doping type (soft and hard admixture of the ferroelectric composite component) on multiferroic composites’ dielectric, ferroelectric, electromechanical, magnetic, and magnetoelectric properties were analyzed. Microstructural studies revealed the microstructure of composites with the correct distribution of the magnetic component in the ferroelectric matrix, suitable for maintaining both the ferroelectric and magnetic properties of composite materials. Research has shown that using a ferroelectric component as the PZT (from the morphotropic region and doped with the ferroelectrically soft niobium admixture) shows many advantages, positively influencing the functional properties of the multiferroic composite. It ensures effective polarization of the composite sample, obtaining a high magnetoelectric effect, which is required in sensors or magnetoelectric converters. PZT with a hard admixture shows higher stability of physical parameters, but its characteristic property also hinders the effective polarization of the composite sample.

Photonic Structure Induced Enhancement in the Triplet State Dynamics of Organic Phosphors at Room Temperature

AbstractTriplet state modification in organic phosphorescence molecules for a desired color and quantum yield is typically pursued by chemical modification. A facile methodology is introduced to tune the triplet state dynamics of a phosphorescent molecule by changing the host‐matrix parameters. An organic phosphor, Br2PmDI (2–Bromo pyromellitic diimide), dispersed at dilute levels (1.5 wt.%) in a semicrystalline high‐κ relaxer ferroelectric host matrix emit room‐temperature phosphorescence accompanied by a delayed fluorescence component. The host relaxer ferroelectric polymer film can be engineered to form a photonic matrix with a regular micropore structure of refractive index contrast ≈0.6 that can increase the density of optical states and introduce photonic coupling. The phosphorescence quantum yield of Br2PmDI in this photonic matrix increases by ≈2.3 fold, and the lifetime reduces by a factor of three. The coupled quantum states are investigated by time‐resolved spectroscopy at different temperatures and pump intensities.

Enhanced Piezoelectricity and Thermal Stability of Electrostrain Performance in BiFeO3-Based Lead-Free Ceramics

BiFeO3-based ceramics possess an advantage over large spontaneous polarization and high Curie temperature, and are thus widely explored in the field of high-temperature lead-free piezoelectrics and actuators. However, poor piezoelectricity/resistivity and thermal stability of electrostrain make them less competitive. To address this problem, (1 - x) (0.65BiFeO3-0.35BaTiO3)-xLa0.5Na0.5TiO3 (BF-BT-xLNT) systems are designed in this work. It is found that piezoelectricity is significantly improved with LNT addition, which is contributed by the phase boundary effect of rhombohedral and pseudocubic phase coexistence. The small-signal and large-signal piezoelectric coefficient (d33 and d33*) peaks at x = 0.02 with 97 pC/N and 303 pm/V, respectively. The relaxor property and resistivity are enhanced as well. This is verified by Rietveld refinement, dielectric/impedance spectroscopy and piezoelectric force microscopy (PFM) technique. Interestingly, a good thermal stability of electrostrain is obtained at x = 0.04 composition with fluctuation η = 31% (Smax'-SRTSRT×100%), in a wide temperature range of 25-180 °C, which is considered as a compromise of negative temperature dependent electrostrain for relaxors and the positive one for ferroelectric matrix. This work provides an implication for designing high-temperature piezoelectrics and stable electrostrain materials.

Study on relaxor polymer interface matrix for piezoelectric nanocomposite generators

Piezoelectric nanocomposites consisting of a polymer matrix and ceramic fillers are candidate components of flexible, wearable, and self-powered electronic devices. The physical discrepancy between ferroelectric polymers and ceramics in a piezoelectric interface makes it difficult to assemble efficient hybrid piezoelectric nanocomposites without polarization and extraneous artifacts. Here, we describe the effect of a relaxor ferroelectric terpolymer matrix on the piezoelectric output, which can enhance the energy harvesting or sensor performance of piezoelectric composite device of nanocomposite generators with filler nanoparticles of lead zirconium titanate. The dielectric property and reduced ferroelectric hindrance of the proposed terpolymer matrix provides more poling to align the polarization of piezoelectric ceramic fillers compared with a normal ferroelectric copolymer matrix. Therefore, relaxor ferroelectric polymers can be better than normal ferroelectric polymers as the matrix of hybrid polymer-ceramic piezoelectric nanocomposite. This research provides important physical information about the interface between a polymer matrix and ceramic fillers in flexible piezoelectric nanocomposite applications.

Remarkable energy-storage performances and excellent stability in CaTiO3-doped BiFeO3-BaTiO3 relaxor ferroelectric ceramics

The actual pulse capacitor application of BiFeO3-based relaxor ferroelectric ceramics has been greatly hindered by low dielectric breakdown strength and poor thermal stability. In this work, these issues are solved by manufacturing nanodomain-engineered and grain-engineered BiFeO3-BaTiO3-CaTiO3 relaxor ferroelectric ceramics. The introduction of CaTiO3 induces nanoscale domains in the ferroelectric BiFeO3-BaTiO3 matrix, bringing about temperature-insensitive dielectric response and almost hysteresis-free polarization field response. Furthermore, largely enhanced dielectric breakdown strengths are also achieved, which is mainly attributed to the refinement of the grain size and the depression of the oxygen vacancy concentration. Consequently, remarkable energy-storage performances with high recoverable energy density (Wrec ∼ 5.03 J/cm3), high efficiency (η ∼ 89.7%), and outstanding thermal stability (Wrec variation < 4% from 30 to 150 ℃) are obtained. Moreover, ultrafast release time (t0.9 ∼ 65 ns) and high power density (∼75.14 MW/cm3) are also achieved, proving the BiFeO3-BaTiO3-CaTiO3 ceramics' enormous potential for underlying advanced pulse capacitor applications.

High-Performance Flexible Piezoelectric Nanogenerator Based on Electrospun PVDF-BaTiO3 Nanofibers for Self-Powered Vibration Sensing Applications

In the present era of intelligent electronics and Internet of Things (IoT), the demand for flexible and wearable devices is very high. Here, we have developed a high-output flexible piezoelectric nanogenerator (PENG) based on electrospun poly(vinylidene fluoride) (PVDF)-barium titanate (BaTiO3) (ES PVDF-BT) composite nanofibers with an enhanced electroactive phase. On addition of 10 wt % BaTiO3 nanoparticles, the electroactive β-phase of the PVDF is found to be escalated to ∼91% as a result of the synergistic interfacial interaction between the tetragonal BaTiO3 nanoparticles and the ferroelectric host polymer matrix on electrospinning. The fabricated PENG device delivered an open-circuit voltage of ∼50 V and short-circuit current density of ∼0.312 mA m-2. Also, the PVDF-BT nanofiber-based PENG device showed an output power density of ∼4.07 mW m-2, which is 10 times higher than that of a pristine PVDF nanofiber-based PENG device. Furthermore, the developed PENG has been newly demonstrated for self-powered real-time vibration sensing applications such as for mapping of mechanical vibrations from faulty CPU fans, hard disk drives, and electric sewing machines.

Coexisting multi-phase and relaxation behavior in high-performance lead-free piezoceramics

Phase boundary engineering (PBE) has remarkably enhanced the piezoelectric properties of potassium sodium niobate {(K, Na)NbO3, KNN} piezoceramics, yet the physical mechanisms need to be further understood. Here we outline a new physical phenomenon to describe piezoelectricity enhancement in KNN-based ceramics with PBE. We propose that the enhancement is due to the multi-phase coexistence featured with strong relaxation behavior. The strong relaxation behavior was unambiguously revealed by cryogenic experiments and originated from the polar nanoregions (PNRs) exhibiting a scale of 2.1 nm and a weak tetragonality (c/a = 1.0040). in situ temperature-dependent experiments uncovered the thermal evolution of the ferroelectric matrix and PNRs in both unpoled and poled samples, the first report in KNN-based ceramics. Our experiments combined with phenomenological theory revealed that ultra-fine nanodomains, PNRs, and easy polarization rotation together promote macro dielectric and piezoelectric properties in the relaxation-featured multi-phase coexistence. This work reveals the physical mechanism from different levels (e.g., local-mesoscopic-macroscopic), thus providing a new systematic understanding of the observed enhancement of piezoelectricity.

Exploration of the mechanisms enabling high performance in relaxor ferroelectric crystals

<p indent="0mm">Relaxor ferroelectric single crystals, exhibiting excellent dielectric, piezoelectric, electro-optic, and pyroelectric properties, are important functional dielectric materials in electronic technology. Since the 1990s, relaxor ferroelectric crystals have attracted considerable attention in the ferroelectric and piezoelectric research fields and improved the performance of numerous piezoelectric devices, especially medical ultrasonic imaging transducers. In this paper, we briefly introduce the history of relaxor ferroelectric crystals and then focus on the research progress of our group in recent years, as listed below. (1) To elucidate the contribution of polar nanoregions (PNRs)<italic> </italic>to piezoelectricity, we performed closely integrated experimental and computational studies on relaxor ferroelectric crystals. In this work, we obtained key experimental evidence (low-temperature dielectric relaxation) for the contribution of PNRs to the piezoelectric activity in relaxor-PbTiO₃ (PT) crystals via cryogenic measurements, and more importantly, for the first time, we quantified the contribution of PNRs accounting for 50%–80% of the room-temperature dielectric and piezoelectric properties. Based on the phase-field simulations, we proposed a mesoscale mechanism wherein the PNRs are aligned in a ferroelectric matrix facilitating the polarization rotation, which successfully explains the contribution of PNRs to dielectric/piezoelectric properties. This work opens up a new material design paradigm that introduces local heterogeneities to achieve enhanced macroscopic responses. (2) Based on the origin of high piezoelectric activity in relaxor ferroelectric crystals, we proposed a theoretical approach, i.e., judiciously introducing local structure heterogeneity, to engineer the interfacial energies, thereby increasing the piezoelectricity of ferroelectric materials. According to this method, we designed and fabricated a series of rare earth element-doped relaxor ferroelectric crystals with piezoelectric coefficients <italic>d</italic>₃₃ in the 3400–4100 pC/N, double the values of the undoped counterparts. The newly developed piezoelectric materials offer potential benefits for piezoelectric devices, especially high-frequency medical transducers, where ultrahigh clamped dielectric constant (~3000) improves the electrical impedance matching of the transducers, thereby increasing the sensitivity and decreasing the insertion loss in the ultracompact transducers. (3) Using phase-field simulations and experimental measurements, we transformed the originally opaque [001]-poled rhombohedral PMN-PT crystals into a transparent one by using an AC electric field to engineer the domain structure. These crystals possess ultrahigh piezoelectric coefficient <italic>d</italic>₃₃ (&gt;2100 pC/N), outstanding electromechanical coupling factor <italic>k</italic>₃₃ (~94%), and large electro-optical coefficient <italic>γ</italic>₃₃<sc>(~220 pm/V),</sc> far beyond the performance of the state-of-the-art transparent ferroelectric crystal LiNbO₃, showing great potential in various hybrid device applications, including photoacoustic medical transducers and self-energy-harvesting touchscreens. Furthermore, we discovered that the larger domain sizes lead to higher piezoelectricity in [001]-poled rhombohedral perovskite ferroelectric crystals, opposing the long-standing belief that a smaller domain size always results in higher piezoelectricity in ferroelectric crystals. This observation may benefit the future design of piezoelectric materials. Finally, the applications of our newly designed relaxor ferroelectric crystals in electromechanical and electro-optical devices are introduced, and the future perspectives of relaxor ferroelectric crystals are discussed.

Fabrication and magnetoelectric investigation of flexible PVDF-TrFE/cobalt ferrite nanocomposite films

Flexible nanocomposite films, with cobalt ferrite nanoparticles (CFN) as the ferromagnetic component and polyvinylidene fluoride–trifluoroethylene (PVDF-TrFE) copolymer as the ferroelectric matrix, were fabricated using a blade coating technique. Nanocomposite films were prepared using a two-step process; the first process involves the synthesis of cobalt ferrite (CoFe2O4) nanoparticles using a sonochemical method, and then incorporation of various weight percentages (0, 2.5, 5, and 10%) of cobalt ferrite nanoparticles into the PVDF-TrFE to form nanocomposites. The ferroelectric polar β phase of PVDF-TrFE was confirmed by x-ray diffraction (XRD). Thermal studies of films showed notable improvement in the thermal properties of the nanocomposite films with the incorporation of nanoparticles. The ferroelectric properties of the pure polymer/composite films were studied, showing a significant improvement of maximum polarization upon 5wt% CFN loading in PVDF-TrFE composite films compared to the PVDF-TrFE film. The magnetic properties of as-synthesized CFN and the polymer nanocomposites were studied, showing a magnetic saturation of 53.7 emu g−1 at room temperature, while 10% cobalt ferrite-(PVDF-TrFE) nanocomposite shows 27.6 emu/g. We also describe a process for fabricating high optical quality pure PVDF-TrFE and pinhole-free nanocomposite films. Finally, the mechanical studies revealed that the mechanical strength of the films increases up to 5 wt% loading of the nanoparticles in the copolymer matrix and then decreases. This signifies that the obtained films could be suited for flexible electronics.

Magnetoelectric Vertically Aligned Nanocomposite of YFeO3 and CoFe2O4

AbstractSelf‐assembled two‐phase vertically aligned nanocomposites consisting of ferromagnetic pillars embedded in a ferroelectric matrix provide an attractive geometry for observing magnetoelectric coupling based on the strain‐coupled magnetostrictive and piezoelectric effects at the interfaces. In perovskite‐spinel nanocomposites the ferroelectric phase typically consists of BiFeO3, BaTiO3 or Pb(Zr,Ti)O3. Here, the ferroelectric phase is Y‐rich YFeO3 which exhibits ferroelectricity originating from the local inversion symmetry breaking caused by YFe antisite defects. Coherent interfaces observed between Y‐rich YFeO3 and a magnetic spinel CoFe2O4 in a vertically aligned nanocomposite enable strain‐mediated magnetoelectric coupling at room temperature, confirming the ferroelectricity and piezoelectricity in Y‐rich YFeO3 and extending the range of magnetoelectric nanocomposite compositions.