Good Piezoelectric Properties Research Articles

Superior piezoelectric properties of lead-free thick-films and their application to alternative multilayer actuator

Abstract CuO-added 0.97(Li0.04Na0.46K0.5)(Nb0.89Sb0.11)O3-0.03CaZrO3 (CLNKNS-CZ) thick-films synthesized at 1060 °C exhibit a dense microstructure comprising small grains and abnormally grown large grains. They have an orthorhombic-tetragonal polymorphic phase boundary structure and exhibit good piezoelectric properties: d33 = 488 pC/N and kp = 0.45. They have a large electric-field induced strain (0.16% at 4.0 kV/mm) which was maintained at 100 °C, whereas the strain decreased slightly to 0.15% at 150 °C. Moreover, a large strain was maintained after 106 electric-field cycles with a maximum electric field of 1.0 kV/mm. Hence, CLNKNS-CZ thick-films exhibit thermally stable strain with good fatigue properties. We synthesized multilayer ceramics comprising five layers of CLNKNS-CZ thick-films and 70Ag–30Pd electrodes with sharp interfaces between ceramic layers and electrodes. Cantilever-type CLNKNS-CZ actuators showed a large displacement (2.5 mm) and acceleration (33.4 G) at 25 V, and similar results were obtained via simulation. Furthermore, the actuating properties of CLNKNS-CZ actuators are comparable to those of PZT-based actuators.

A mini review on the generation of crimped ultrathin fibers via electrospinning: Materials, strategies, and applications

Structures modification of fibers has been attracting significant attention in various fields and applications. Among different techniques of fabricating ultrathin fibers, electrospinning is the most commonly adopted method because of the ease of forming fibers with a wide range of properties and its exceptional advantages, such as the ability to spin into different shapes and sizes, as well as the adaptable porosity of electrospun fiber webs. The crimped structure has been attracting the attention of scientific researchers owing to its unique properties (eg, spring‐like behavior, supreme strain, remarkable specific surface area, good piezoelectric properties, excellent biological properties, and so on). Therefore, this study summarizes a review of the strategies and methods, reported so far, of generating electrospun crimped ultrathin fibers of various polymers. The review focuses on the polymer types, formation methods, characterizations, and applications of the electrospun crimped ultrathin fibers. We believe this work can serve as an important reference for the materials, strategies, and applications of crimped fibers.

Fabrication of Poly(vinylidene fluoride)/Multiwalled carbon nanotube nanocomposite foam via supercritical fluid carbon dioxide: Synergistic enhancement of piezoelectric and mechanical properties

The fabrication of poly(vinylidene fluoride) (PVDF) based foam with complicated three-dimensional (3D) geometry and excellent piezoelectric property remains great challenge worldwide. In this study, microcellular PVDF/multiwalled carbon nanotube (MWCNT) nanocomposite foaming part was fabricated by supercritical carbon dioxide (scCO2) bead foaming technology. With the assistance of the ball milling, the good dispersion of MWCNT particles in PVDF matrix was achieved, which promoted the heterogeneous nucleation and enhancement effects of MWCNT on PVDF, resulting in the formation of more unique and denser cells, e.g. from 3.4 × 105 cells/cm3 of pure foam to 1.7 × 106 cells/cm3 of the composite foam when MWCNT content was 1.5%, and high compression strength, i.e. 3.1 MPa with 1.5% MWCNT at 10% compressive strain, about 1.1 MPa higher than that of pure foam. During the bead foaming process, the induced crystallization effect of MWCNT as well as the plasticizing and squeezing effect of scCO2 on PVDF matrix contributed to the increase of the β-phase crystal in PVDF matrix, thus endowing the composite foaming part with good piezoelectric property, i.e. 6.5 V of output voltage under periodic compression, which lightened 4 LEDs and made the foaming part had wide potential application in smart electronic field.

Research progress of high piezoelectric activity of potassium sodium niobate based lead-free ceramics

Due to excellent piezoelectric properties and electromechanical coupling properties, lead-based piezoelectric ceramics represented by lead zirconate titanate Pb(Zr<sub><i>x</i></sub>Ti<sub>1–<i>x</i></sub>)O<sub>3</sub> (PZT) are widely used in science and technology, industry, military and daily life. However, the content of Pb in PZT-based ceramics exceeds 60% (mass ratio), which will cause serious damage to human ecological environment in the process of their production, use and waste treatment. Therefore, the development of lead-free piezoelectric ceramics has become one of the hot research spots. Potassium sodium niobate (K<sub>0.5</sub>Na<sub>0.5</sub>)NbO<sub>3</sub> (KNN) lead-free piezoelectric ceramics are considered as one of the most promising material systems to substitute for lead-based piezoelectric ceramics because of their good piezoelectric properties and higher Curie temperature. Through many years of researches, the piezoelectric properties of modified KNN based lead-free piezoelectric ceramics have approached to or even exceeded those of some lead-based piezoelectric ceramics. Combining with our relevant work, we comprehensively review the research progress of high piezoelectric activity of KNN based lead-free piezoelectric ceramics, especially focus on the research progress of high-performance potassium sodium niobate lead-free piezoelectric ceramics, preparation technology and related theoretical mechanisms. The future research direction and prospect of KNN-based lead-free piezoelectric ceramics are also presented.

Research progress of piezoelectrets based micro-energy harvesting

<sec>In this paper, the progress of micro-energy harvesters by using piezoelectret-based transducers as a core element is reviewed, including basic physical principle and properties of piezoelectrets, and their applications in micro-energy harvesting. Piezoelectret is electret-based piezoelectric polymer with a foamed structure. The piezoelectric effect of such material is a synergistic effect of the electret property of the matrix polymer and the foam mechanical structure in the material. Piezoelectret, featuring strong piezoelectric effect, flexibility, low density, very small acoustic impedance and film form, is an ideal electromechanical material for lightweight flexible sensors and mechanical energy harvesters. The piezoelectret prepared by means of grid, template patterning, supercritical CO<sub>2</sub> assisted low-temperature assembly, lithography mold combined with rotary coating and hot pressing has regular voids and good piezoelectric properties. Piezoelectret has been used to harvest vibrational energy, human motion energy and sound energy. </sec><sec>According to the stress direction applied to the piezoelectrets, operating modes of energy harvesters can be divided into 33 and 31 modes. The vibrational energy harvesters based on piezoelectret are utilized to harvest medium frequency vibrational energy generated by factory machines, aircrafts, automobiles, etc. Such energy harvesters can generate considerable power even in a small size. Human motion energy harvesters are generally used to power wearable sensors. The high sensitivity, lightweight, and flexibility of the piezoelectret make such a material a promising candidate for harvesting human motion energy. Owing to very small acoustic impedance, high figure-of-merit, flat response in audio and low-frequency ultrasonic range, the piezoelectrets are more appropriate for acoustic energy harvesting in air medium than conventional PZT and ferroelectric polymer PVDF.</sec><sec>In the future, specific micro-energy harvesters using piezoelectrets as transduction material can be designed and fabricated according to the practical application environment, and their performance can be enhanced by using flexible connections of transduction elements.</sec>

Ferroelectric P(VDF-TrFE)/POSS nanocomposite films: compatibility, piezoelectricity, energy harvesting performance, and mechanical and atomic oxygen erosion.

Poly(vinylidene difluoride) (PVDF) and its copolymers as the polymers with the highest piezoelectric coefficient have been widely used as sensors and generators. However, their relatively low performances limit their applications in some harsh environments. In this work, piezoelectric poly(vinylidene-trifluoroethylene) P(VDF-TrFE) matrices with different amounts of polyhedral oligomeric silsesquioxane (POSS) were prepared by a low temperature solvent evaporation method and thermal poling. The morphology, surface performance, crystalline phase, and piezoelectric and ferroelectric properties of the nanocomposites were investigated and the influence of POSS on these performances was studied. POSS had good compatibility with P(VDF-TrFE) and did not affect the crystalline phase formation of the matrix. The composites presented good piezoelectric properties. Piezo- and triboelectric nanogenerators were designed and fabricated. The voltage and current outputs were analyzed and the polarization effect was evaluated. The average output voltage and the current density of the matrix were 3 V and 0.5 μA cm−2 when subjected to a force of 38 N on an area of 1 cm2. The mechanical properties of P(VDF-TrFE)/POSS nanocomposites were also studied by the nanoindentation test. The hardness and modulus of samples increased 20% and 17% with a low addition of POSS. Atomic oxygen erosion properties of the composites were numerically simulated by the Monte Carlo method. The erosion cavity shape and depth were compared and studied. The influence of POSS addition on the P(VDF-TrFE) matrix and the associated reinforcing mechanism were analyzed.

Исследование свойств наноструктур оксида цинка, полученных методом импульсного электрохимического осаждения

The properties of zinc oxide nanostructures allow it to be used in various fields of science and technology. The increased interest in this compound is caused by a rare combination of optical and electrophysical properties. The films of this compound have good piezoelectric and electroluminescent properties, due to which zinc oxide can be used as functional layers in surface acoustic waves, elements of nonlinear optics. This allows the oxide to pass visible radiation. In this paper, we study the influence of the conditions for obtaining a coating by pulsed electrochemical deposition on the forbidden zones and the power of a coating based on zinc oxide. It was shown that the temperature and duty cycle of pulses are of great importance in the formation of the coating, which is explained by the kinetics of the electrochemical reaction. The Urbach energy increases with a decrease in crystalline size and increased by almost 3 times, compared with a coarse-grained sample.

Electrophysical Properties of PMN-PT-Ferrite Ceramic Composites.

Ferroelectromagnetic composites based on (1−x)PMN-(x)PT (PMN-PT) powder and Ni-Zn ferrite powder were obtained and are described in this work. As a ferroelectric component, we used (1−x)PMN-(x)PT solid solution (with x = 0.25, 0.28, 0.31, 0.34, 0.37, 0.40), synthesized using the sol-gel method. As a magnetic component, we used nickel-zinc ferrite, obtained using classic ceramic technology. The six compositions of PMN-PT used have rhombohedral symmetry, tetragonal one and mixture of these phases (morphotropic phase area), depending on x. The final ceramic composite samples were obtained using the classic methods involving the calcination route and pressureless final sintering (densification). The properties of the obtained ceramic composite samples were investigated, including microstructure SEM (scanning electron microscope), dielectric properties, electromechanical properties, and DC (Direct Current) electrical conductivity. Results showed that the microstructures of the PP-F composite samples characterized by larger grains were better crystallized, compared with the microstructures of the PMN-PT ceramic samples. The magnetic properties do not depend on the ferroelectric component of the composite samples, while the insertion of ferrite into the PMN-PT compound reduces the values of remnant and spontaneous polarization, as well as the coercive field. The dielectric measurements also indicated that the magnetic subsystem influences the dielectric properties. The present results show that the PP-F ceramic composite has good dielectric, magnetic, and piezoelectric properties, which predisposes this type of material to specific applications in microelectronics and micromechatronics.

BNT‐based ferroelectric ceramics: Electrical properties modification by Ta2O5 oxide addition

AbstractDue to their superior piezo‐responses (strain S > 0.3%), bismuth sodium titanate (BNT)‐based relaxor ferroelectrics have received much attention. Compared to other chemical elements, tantalum (Ta) doping provides superior electro‐strain for these ferroelectrics, while the effect of Ta2O5 as oxide additive has been rarely reported. Herein, lead‐free piezoceramics of Bi0.5(Na0.72K0.22Li0.06)0.5TiO3‐xTa2O5 (BNKLT‐xTa2O5, x = 0‐0.015) are synthesized. We study the effects of Ta2O5 addition on the crystal structure, piezoelectric responses, dielectric properties, and ferroelectric properties of BNKLT ceramics. All of the ceramics exhibit a typical perovskite structure, and Ta2O5 diffuses into the BNKLT lattice to form a uniform solid solution. The addition of Ta2O5 can make the grains more regular and uniform, while excess Ta2O5 result in finer grains. The undoped BNKLT ceramics show good ferroelectric and piezoelectric properties (remnant polarization Pr = 22.5 μC/cm2 and piezoelectric coefficient d33 = 250 pC/N); however, the addition of Ta2O5 leads to an clear degradation in d33 and Pr. Meanwhile, the addition of an appropriate Ta2O5 amount leads to an increase in the electro‐strain, and the unipolar strain reaches 0.385% under 60 kV/cm for x = 0.003, together with a higher normalized strain (d33*=Smax/Emax) of 633 pm/V (x = 0.003). The enhanced strain behaviors can be attributed to the coexistence of the ferroelectric and relaxor states, and an excellent electrostriction coefficient Q33 (Q33 = S/P2) value of 0.038 m4C−2 is obtained under 60 kV/cm for x = 0.003.

Modified sepiolite/PVDF‐HFP composite film with enhanced piezoelectric and dielectric properties

ABSTRACTFlexible film with both piezoelectric and dielectric properties is considered to be a potential candidate for the energy conversion and storage devices. In this study, the Li+ and H2O modified sepiolite/poly(vinylidene fluoride‐co‐hexafluoropropylene) (LiSEP‐H2O/PVDF‐HFP) composite films with both good piezoelectric and dielectric properties were prepared by traditional coating process. When the H2O content was 13 wt %, the LiSEP‐H2O/PVDF‐HFP composite exhibited high d33 of 32 and dielectric constant of 48. Moreover, the effects of the Li+ and adsorbed H2O on the d33, F(β), dielectric constant, short‐circuit currents were discussed. The adsorbed H2O enhanced the β‐phase by the hydrogen bonds and Li+ improved the polarization to realize the composite film with increased piezoelectric and dielectric properties respectively. We expected the common modification to lead other clay minerals realizing the future applications in the adjustment of composites' electric properties. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48412.

The effect of stress state on AlN thin films and AlN/Finemet magnetoelectric composite device

Piezoelectric aluminum nitride (AlN) thin films with high c-axis oriented were deposited on Fe73.5Cu1Nb3Si13.5B9 (Finemet) substrates using a pulsed DC magnetron sputtering system. The influences of stress state on piezoelectric properties of AlN thin films, and magnetoelectric (ME) coupling properties of AlN/Finemet device have been investigated. The result shows that samples with flat state have a good piezoelectric property of 1.71 pm/V, which is higher than samples with compressive state and tensile state. It has been found that the stress state of the sample has a significant effect on magnetoelectric coupling coefficient. The ME coupling coefficient αME of samples were measured as 212.5 V/cm Oe (flat state), 167.5 V/cm Oe (compressive state), 141.6 V/cm Oe (tensile state), which is potential for weak magnetic field measurement.

3D printing of electroactive PVDF thin films with high β-phase content

Bi-axially oriented electroactive PVDF thin films were prepared by a 3D printing process during which multiple parameters play a critical role in enhancing β-phase and crystallinity of the thin films. The PVDF molecular chains were rotated and stretched to form orderly arrangement by the pulling of in situ strong auxiliary electric potential (voltage) and the mechanical pulling force, and the aligned PVDF molecular chains improved the crystallinity of the thin films. Doping very small amount of multi-walled carbon nanotubes (MWCNTs) or graphene (GR) as a nucleating agent significantly increased the content of the β-phase in the films. Adding GR behaved is better than the MWCNTs in improving the β-phase due to the lamellar structure of graphene can generate a large number of micro electric fields stimulating the transformation of molecular chain from trans-gauche-trans-gauche(TG+TG−) to all-trans (TTTT). The content of β-phase in the PVDF/GR(0.03 wt%) composite thin film researched at 61.52%. Under the special environment of 3D printing, the printed PVDF thin films became very dense with high β-phase after depositing layer-by-layer. It exhibited good piezoelectric properties without post-poling treatment and mechanical stretching.

Microscopic study of polydopamine modified BaTiO3/poly(vinylidene fluoride-trifluoroethylene) nanocomposite films

Poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] has been intensively studied because of its good piezoelectric properties and at the same time being flexible and bio-compatible, making it a strong candidate for biomedical application. Doping with inorganic piezoceramic nanoparticles will enhance its ferro−/piezoelectricity. Further enhancements in ferro−/piezoelectricity of P(VDF-TrFE) are expected from surface modification of the nanoparticles through improving the bonding between the nanoparticles and polymer matrix. In this paper, a piezoresponse force microscopy (PFM) study on P(VDF-TrFE) doped with polydopamine modified BaTiO3 (BT-Pdop) nanoparticles is introduced. The microscopic study is complicated by the fine domain structures. As ferro−/piezoelectricity is directly related with domain size, instead of a domain-wise study, a statistical correlation (domain size) analysis was carried out for this composite. Since PFM measurement is based on the converse piezoelectric effect (the first harmonic response of the sample surface upon the applied electric stimulation), topographical effects should be taken into account in analyzing the related piezoresponse images. Hence, the correlation lengths of both topographical and piezoresponse images on the same area were studied. The doping dependence of the correlation length of BT-Pdop/P(VDF-TrFE) behaves differently for piezoresponse (polarization) and topography (grain) images. In particular, the correlation lengths of piezoresponse and topography images are in different ranges: 23–29 nm for the former and 55–66 nm for the latter; also, the composition dependences are different. Accordingly, the piezocorrelation reflects the material's real piezoresponse. It can also be deduced that the macroscopic polarization behavior in Pdop-BT/P(VDF-TrFE) results from extrinsic contributions.

Flexible polyvinylidene fluoride based nanocomposites with high and stable piezoelectric performance over a wide temperature range utilizing the strong multi-interface effect

Because of the good piezoelectric properties among polymers, poly(vinylidene fluoride) (PVDF) has been extensively applied in constructing flexible sensors and energy harvesters. Recent progress towards high performance sensors and energy harvesters has trigged significant interest in the fabrication of PVDF materials with superior piezoelectricity and good thermal piezoelectric stablility. Herein, we reported a flexible PVDF based nanocomposite that maintained high and stable piezoelectricity over a wide temperature range from 10 to 100 °C through the strong multi-interface effect. In this work, PVDF was firstly blended with poly(vinylidene fluoride-co-hexafluropropylene) (PVDF-HFP), and then dopamine modified BaTiO3 hollow nanoparticles were introduced into the blend polymer matrix. Through optimizing the fabrication process and modulating the mass ratio of PVDF-HFP and BaTiO3, notably strenghthened ferroelectricity and piezoelectricity was achieved in the final composites, wherein the piezoelectric coefficient d33 reached a peak of 40 pC/N and showed good retention with increasing temperatures up to 100 °C.

Pseudocubic-based polymorphic phase boundary structures and their effect on the piezoelectric properties of (Li,Na,K)(Nb,Sb)O3-SrZrO3 lead-free ceramics

CuO-added 0.96(LixNa0.5-xK0.5)(Nb1-ySby)O3-0.04SrZrO3 ceramics were sintered at 1020 °C for 6 h. Various crystal structures were synthesized in these specimens by controlling the Li2CO3 (x) and Sb2O5 (y) contents: pseudocubic, orthorhombic-pseudocubic polymorphic phase boundary (PPB), tetragonal-pseudocubic PPB, orthorhombic-tetragonal-pseudocubic PPB, and orthorhombic-tetragonal PPB structures. The pseudocubic structure developed in these specimens was similar to the R3m rhombohedral structure instead of the Pm3m cubic structure because the specimens with a pure pseudocubic structure showed good ferroelectric and piezoelectric properties. The piezoelectric properties of the specimens were influenced by their crystal structures. The specimen with the tetragonal-pseudocubic PPB structure showed the best piezoelectric properties because this structure was similar to the tetragonal-rhombohedral morphotropic phase boundary structure developed in Pb(Zr1-xTix)O3-based ceramics. In particular, the specimen with the tetragonal-pseudocubic PPB structure corresponding to x = 0.05 and y = 0.065 showed the largest d33 and kp values of 431 pC/N and 0.43, respectively.

Electrical properties and microstructure of phase combination in BaTiO3-based Ceramics

Perovskite barium titanate (BaTiO3) ceramics are widely used in electronics industries such as capacitors, sensors and actuators. BaTiO3-based ceramics have good dielectric, ferroelectric and piezoelectric properties. BaTiO3 powder was fabricated by mixed-oxide method via a vibro-milling technique. The pellets were then placed in a high purity alumina crucible in air and sintered at 1375 °C for 1, 2, 4, 6 and 8h. X-ray diffraction technique was used to investigate phase formation of BaTiO3 ceramics. Grain size was measured by scanning electron microscopy (SEM). The computer-controlled dielectric measurement system consisted of a high precision LCR-meter. Electric field induced polarization was measured by Sawyer-Tower circuit. In this work, the effect of phase combination in BaTiO3 ceramics on electrical properties (dielectric and electric field induced polarization) and microstructure was investigated.

Influence of compositional ratio K/Na on structure and piezoelectric properties in [(Na1−xKx)0.5Bi0.5]Ti0.985Ta0.015O3 ceramics

[(Na1−xKx)0.5Bi0.5]Ti0.985Ta0.015O3 (abbreviated as Ta-NK100x) lead-free ceramics with good piezoelectric properties were prepared using a solid-state reaction method. The structure and electrical properties of Ta-NK100x had been systemically investigated. The highest bipolar strain of 0.458% and the unipolar strain 0.448% are achieved at x = 0.18 at 60 kV/cm. Meanwhile, the corresponding normalized strain $$ \left( {d_{33}^{*} } \right) $$ reaches 747 pm/V. In addition, the unipolar strain of the poled Ta-NK18 increases to 0.537%, and corresponding $$ d_{33}^{*} $$ increases slightly to 894.5 pm/V at 60 kV/cm. The electric-field-induced phase transition between ferroelectric and relaxor is found to play a dominant role in the origin of the large strain. Moreover, the strain behavior remains stable within 105 switching cycles which indicating the prepared ceramics are promising candidates for actuators and stress sensors.

Design on improving piezoelectric strain and temperature stability of KNN‐based ceramics

AbstractLead‐free 0.99(0.96K0.46Na0.54Nb1‐xTaxO3‐0.04Bi0.5(Na0.82K0.18)0.5ZrO3)‐0.01CaZrO3 (0.99(0.96KNNTax‐0.04BNZ)‐0.01CZ) ceramics were prepared by a solid‐state sintering method. Ta2O5 doped in the 0.99(0.96KNNTax‐0.04BNZ)‐0.01CZ ceramics results in a phase structure transition from the orthorhombic (O)/tetragonal (T) phase to the rhombohedral (R)/T phase. The Ta2O5 dopant induces a decrease in the average grain size from ~1.70 to ~0.69 μm. At x = 0.02 and 0.04, the ceramics have a high reverse piezoelectric coefficient (~500 pm/V under 25 kV/cm). The ceramics with x = 0.04 show an optimal level of unipolar strain, reaching 0.17% under 35 kV/cm at room temperature, and their field‐induced strain varies <10% in the temperature range from 25 to 135°C. The presence of the O phase in the polymorphic phase boundary (PPB) improves the temperature stability the reverse piezoelectric coefficient (). Obtaining KNN‐based ceramics with good piezoelectric properties and weak temperature sensitivity by designing a R/O/T phase boundary and controlling the average grain size to the submicrometer level is highly feasible.

Low sintering temperature for lead‐free BiFeO3‐BaTiO3 ceramics with high piezoelectric performance

AbstractThrough modification of the heat‐treatment process using a higher heating rate and a lower binder burnout temperature, the piezoelectric performance of water‐quenched 0.67Bi1.05FeO3‐0.33BaTiO3 (BF33BT) lead‐free piezoelectric ceramics was improved. The observed physical properties of BF33BT ceramics were very sensitive to the process temperatures. The sintering temperature (TS) was changed within a narrow temperature range, and its effects were investigated. The largest rhombohedral distortion (90°‐αR = 0.14°) and tetragonality (cT/aT = 1.022) were observed for the ceramic sintered at 980°C, and its Curie temperature was 476°C. This ceramic showed good piezoelectric properties and large grains; the piezoelectric sensor charge coefficient (d33) was 352 pC/N, and the piezoelectric actuator charge coefficient () was 270 pm/V. The high piezoelectric performance and low TS of BF33BT ceramics indicate their potential as new low‐cost eco‐friendly lead‐free piezoceramics.

Strong magnetoelectric coupling of Aurivillius phase multiferroic composite films with similar layered perovskite structure

Aurivillius phase Bi5Ti3FeO15/Na0.5Bi4.5Ti4O15 multiferroic composite films were synthesized using a sol-gel technique. Multiferroic properties and magnetoelectric coupling effect of composite films were investigated. The domain structures were clearly observed, which prove that composite films endow with good ferroelectric polarization. The maximum piezoelectric coefficient is up to 235 pm/V at 20 V, which proves that good electrostrictive and piezoelectric properties are obtained. The composite films exhibit enormous magnetoelectric voltage coefficient with αE = 410 mV/cm·Oe in magnetic field of Hbias = 7.6 kOe at room temperature, which is ascribed to good ferromagnetic, piezoelectric properties and interface coupling between Bi5Ti3FeO15 and Na0.5Bi4.5Ti4O15 layers. This work not only provides a new idea but also greatly improves the magnetoelectric effect of composite films, which makes magnetoelectric effect more effective in practice.