Large Piezoelectric Coefficient Research Articles

Unexpectedly high piezoelectricity of Sm-doped lead zirconate titanate in the Curie point region

Large piezoelectric coefficients in polycrystalline lead zirconate titanate (PZT) are traditionally achieved through compositional design using a combination of chemical substitution with a donor dopant and adjustment of the zirconium to titanium compositional ratio to meet the morphotropic phase boundary (MPB). In this work, a different route to large piezoelectricity is demonstrated. Results reveal unexpectedly high piezoelectric coefficients at elevated temperatures and compositions far from the MPB. At temperatures near the Curie point, doping with 2 at% Sm results in exceptionally large piezoelectric coefficients of up to 915 pm/V. This value is approximately twice those of other donor dopants (e.g., 477 pm/V for Nb and 435 pm/V for La). Structural changes during the phase transitions of Sm-doped PZT show a pseudo-cubic phase forming ≈50 °C below the Curie temperature. Possible origins of these effects are discussed and the high piezoelectricity is posited to be due to extrinsic effects. The enhancement of the mechanism at elevated temperatures is attributed to the coexistence of tetragonal and pseudo-cubic phases, which enables strain accommodation during electromechanical deformation and interphase boundary motion. This work provides insight into possible routes for designing high performance piezoelectrics which are alternatives to traditional methods relying on MPB compositions.

Effects of sintering temperature and KBT content on microstructure and electrical properties of (Bi.5Na.5)TiO3-BaTiO3-(Bi.5K.5)TiO3 Pb-free ceramics

A route exploring the morphotropic phase boundaries (MPB) region in (Bi.5Na.5)TiO3-BaTiO3-(Bi.5K.5)TiO3 ternary system has been designed based on the phase diagram. X-ray diffraction (XRD) has been performed to determine the phases of the prepared samples. The dielectric, ferroelectric, and piezoelectric properties of [(1-x) 0.9363(Bi.5Na.5)TiO3–0.0637BaTiO3]-x(Bi.5K.5)TiO3 (BNKBT100x) ternary lead-free piezoelectric ceramics are investigated as the functions of x and sintering temperature. When x was varied from 0 to 0.11, the BNKBT100x ceramics show single perovskite structure sintered at 1130–1210 °C. These ceramics show large dielectric permittivity, small dielectric loss, and diffused phase transition behavior. Well-defined ferroelectric polarization-electric field (P-E) hysteresis loop and relative large piezoelectric and electromechanical coefficients are also found in these ceramics. When increasing x, the electrical performances first increase, then decrease. The same rule is found when varying the sintering temperature. The optimized composition and sintering temperature are finally obtained.

Magnetoelectric effect in stretch-shear mode self-biased LiNbO3 based composite with high-frequency resonant response

Magnetoelectric (ME) composites have received attention abidingly due to the promising potential applications in magnetic field sensor and energy harvester. In recent years, shear mode ME composite was frequently discussed with promising applications in high-frequency magnetic field with large signal-to-noise ratio. Single-crystal LiNbO3, as a lead-free piezoelectric phase with high mechanical quality factor and small dielectric constant, is suitable for achieving a large shear ME effect with large shear piezoelectric coefficient d15 or d24, and different piezoelectric coefficients can be obtained by crystal-cut transformation. The transformation rule of shear ME coefficient with transformation of LiNbO3 crystal orientation and the MHz high-frequency magnetic detection is still lacking. Furthermore, self-biased ME composite can be obtained with SrFe12O19 ribbon, which is useful for the integration and miniaturization of ME sensor. In the present work, we use a series of X-cut LiNbO3 to obtain different d15 or d16 in a stretch-shear ME composite. Piezoelectric coefficient d15 and ME coefficient E15 of Metglas/LiNbO3 composite are obtained in experiment, respectively. The results show that LiNbO3 xzt/30 has the largest d15 and E15, and the transformation rule of E15 is consistent with the coordinate transformation of d15. The structure of stretch-shear ME composite is optimized to improve the ME coefficient. Then the stretch-shear mode self-biased SrFe12O19/Metglas/LiNbO3 composite is fabricated, and shear ME response is observed under zero external direct current magnetic bias. Moreover, E15 at electromechanical resonance frequency is gained at shear-mode high frequency (0.991 MHz and 3.51 MHz). The largest ME coefficient E15 is acquired in the stretch-shear 5-foil Metglas/LiNbO3 (xzt/30) composite of 134.16 mV/(cmOe) at 1 kHz and 9.17 V/(cm Oe) at 3.51 MHz. This work is beneficial to the confirming of the corresponding rules of shear ME coefficient and LiNbO3 piezoelectric coefficient, showing that the composite possesses the potential applications in integration, miniaturization and high-frequency resonant sensor.

Unveiling the Influence of Surface Fermi Level Pinning on the Piezoelectric Response of Semiconducting Nanowires

AbstractZnO nanowires (NWs) are excellent candidates for the integration of energy harvesters, mechanical sensors, piezotronic and piezophototronic devices. However, ZnO NWs are usually nonintentionally n‐doped during their growth. Thus, it can be expected theoretically that their piezoelectric response be degraded and mostly geometry‐independent as a result of strong screening effects by free carriers, while experimentally many NW‐based piezoelectric transducers demonstrate quite reasonable performance. In this paper, this apparent contradiction is explained by surface Fermi level pinning (SFLP). Simulations based on the finite element method are developed to investigate the influence of SFLP on the electrical response of ZnO piezogenerators based on arrays of vertical ZnO NWs (the so‐called VING) operated in compression or bending mode. The results show that the nonsymmetrical response with respect to loading direction, which has been observed experimentally when the VING is bent, can be explained when account is taken of the reverse piezoelectric effect associated with SFLP. Influence of geometry and comparison to thin film are also discussed. It is found that the performance improvement, which is observed experimentally at scales much larger than predicted by ab initio models when NWs are compared to thin films, can be partly related to SFLP effects rather than larger piezoelectric coefficients.

Low-temperature-sintered Bi0.5Na0.5TiO3-based lead-free ferroelectric ceramics with good piezoelectric properties

Li2CO3 has been used as a sintering aid for fabricating lead-free ferroelectric ceramic 0.93(Bi0.5Na0.5TiO3)-0.07BaTiO3. A small amount (0.5wt%) of it can effectively lower the sintering temperature of the ceramic from 1200°C to 980°C. Unlike other low temperature-sintered ferroelectric ceramics, the ceramic retains its good dielectric and piezoelectric properties, giving a high dielectric constant (1570), low dielectric loss (4.8%) and large piezoelectric coefficient (180 pC/N). The “depolarization” temperature is also increased to 100°C and the thermal stability of piezoelectricity is improved. Our results reveal that oxygen vacancies generated from the diffusion of the sintering aid into the lattices are crucial for realizing the low temperature sintering. Owing to the low sintering temperature and good dielectric and piezoelectric properties, the ceramics, especially of multilayered structure, should have great potential for practical applications.

Large Piezoelectric Effect in a Lead-Free Molecular Ferroelectric Thin Film.

Piezoelectric materials have been widely used in various applications, such as high-voltage sources, actuators, sensors, motors, frequency standard, vibration reducer, and so on. In the past decades, lead zirconate titanate (PZT) binary ferroelectric ceramics have dominated the commercial piezoelectric market due to their excellent properties near the morphotropic phase boundary (MPB), although they contain more than 60% toxic lead element. Here, we report a lead-free and one-composition molecular ferroelectric trimethylbromomethylammonium tribromomanganese(II) (TMBM-MnBr3) with a large piezoelectric coefficient d33 of 112 pC/N along polar axis, comparable with those of typically one-composition piezoceramics such as BaTiO3 along polar axis [001] (∼90 pC/N) and much greater than those of most known molecular ferroelectrics (almost below 40 pC/N). More significantly, the effective local piezoelectric coefficient of TMBM-MnBr3 films is comparable to that of its bulk crystals. In terms of ferroelectric performance, it is the low coercive voltages, combined with the multiaxial characteristic, that ensure the feasibility of piezo film applications. Based on these, along with the common superiorities of molecular ferroelectrics like light weight, flexibility, low acoustical impedance, easy and environmentally friendly processing, it will open a new avenue for the exploration of next-generation piezoelectric devices in industrial and medical applications.

Large piezoelectric strain with ultra-low strain hysteresis in highly c-axis oriented Pb(Zr0.52Ti0.48)O3 films with columnar growth on amorphous glass substrates

Thin films of PbZr0.52Ti0.48O3 (PZT) with largely detached columnar grains, deposited by pulsed laser deposition (PLD) on amorphous glass substrates covered with Ca2Nb3O10 nanosheets as growth template and using LaNiO3 electrode layers, are shown to exhibit very high unipolar piezoelectric strain and ultra-low strain hysteresis. The observed increase of the piezoelectric coefficient with increasing film thickness is attributed to the reduction of clamping, because of the increasingly less dense columnar microstructure (more separation between the grains) with across the film thickness. A very large piezoelectric coefficient (490 pm/V) and a high piezoelectric strain (~0.9%) are obtained in 4-µm-thick film under an applied electric field of 200 kV/cm, which is several times larger than in usual PZT ceramics. Further very low strain hysteresis (H≈2–4%) is observed in 4 to 5 µm thick films. These belong to the best values demonstrated so far in piezoelectric films. Fatigue testing shows that the piezoelectric properties are stable up to 1010 cycles. The growth of high quality PZT films with very large strain and piezoelectric coefficients, very low hysteresis and with long-term stability on a technologically important substrate as glass is of great significance for the development of practical piezo driven microelectromechanical actuator systems.

Composition design and electrical properties of (K0.48Na0.52)NbO3-xLiSbO3}-y{(Bi0.5Na0.5)(Zr1-zSnz)O3} ceramics

In the present study, we designed a new system, (K0.48Na0.52)NbO3-xLiSbO3}-y{(Bi0.5Na0.5)(Zr1-zSnz)O3} and systemically investigated both the piezoelectric performance under weak field and the electrostrain under large electric field. Here the isovalent additive LiSbO3 (LS) was employed to pinch the three ferroelectric phases together, while the aliovalent dopant (Bi0.5Na0.5)(Zr0.8Sn0.2)O3 (BNZS) was introduced to further lower the Curie temperature (Tc). The enhanced piezoelectric properties were achieved by pinching the phases with different symmetries together; hereinto the ceramic with LS content of 0.05 and BNZS content of 0.03 exhibited large piezoelectric coefficient (d33) of 249pC/N. Besides the high piezoelectric performance under weak field, the present ceramics also exhibited large electrostrain under large electric field, ascribing to the Zr4+ and Sn4+ in BNZS. The electrostrain reached 0.27% under the electric field of 4kV/mm (with the converse piezoelectric coefficient d33* of 675pm/V), even superior to the widely used hard PZT.

Coexistence of three ferroelectric phases and enhanced piezoelectric properties in BaTiO3–CaHfO3 lead-free ceramics

Perovskite ferroelectrics possess the fascinating piezoelectric properties near a morphotropic phase boundary, attributing to a low energy barrier that the results in structural instability and easy polarization rotation. In this work, a new lead-free system of (1-x)BaTiO3-xCaHfO3 was designed, and characterized by a coexistence of ferroelectric rhombohedral-orthorhombic-tetragonal (R-O-T) phases. With the increase amount of CaHfO3 (x), a stable coexistence region of three ferroelectric phases (R-O-T) exists at 0.06≤x≤0.08. Both large piezoelectric coefficient (d33∼400pC/N), inverse piezoelectric coefficient (d33*∼547pm/V) and planar electromechanical coupling factor (kp∼58.2%) can be achieved for the composition with x=0.08 near the coexistence of three ferroelectric phases. Our results show that the materials with the composition located at a region where the three ferroelectric R-O-T phases coexist would have the lowest energy barrier and thus greatly promote the polarization rotation, resulting in a strong piezoelectric response.

Ferroelectric Gd-doped ZnO nanostructures: Enhanced dielectric, ferroelectric and piezoelectric properties

Gadolinium doped ZnO nanorods were grown by wet chemical method. Line broadening of each diffraction peak was studied to evaluate the crystallite size, lattice strain, stress and energy density. Crystallite size was estimated by Scherrer and Williamson-Hall methods. The size was found to be in good agreement with the results of transmission electron microscopy. As a result of Gadolinium doping, high remnant polarization (Pr = 0.29 μC/cm2) and coercive field (Ec = 16.41 kV/cm) were observed. The decrease in leakage current due to Gadolinium doping makes ZnO a remarkable candidate for ferroelectric capacitor. High ferroelectric phase transition temperature (Tc = 215 °C) and large piezoelectric coefficient (d33 = 45.49 pm/V) were observed which makes Gadolinium doped ZnO sample useful for high temperature non-volatile ferroelectric memory applications.

Ferro-/pyroelectric response of 0.57BF-0.31PMN-0.12PT ternary ceramic far away from morphotropic phase boundaries

A ternary BiFeO3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (BF-PMN-PT) solid solution with a composition far away from morphotropic phase boundaries (MPB) has been synthesized by solid-state reaction method. XRD analysis revealed a pure perovskite phase without any trace of pyrochlore phase. The system exhibited a broad phase transition with transition temperature Tc ~ 285°C. The hysteresis loop of the ceramics displayed high remanent polarization (Pr ~ 41.23μC/cm2) and coercive field (Ec ~ 35.41kV/cm). The true-remanent polarization after removing the non-remanent components was evaluated by remanent hysteresis and PUND tasks, which revealed the actual usable polarization component for memory devices. Time-dependent compensated plots confirmed the resistive-leakage free characteristic of the BF-PMN-PT ceramics which makes them useful for application in devices like actuators where the electric field is switched at different rates. Fatigue test showed the ferroelectric parameters (switching and non-switching polarization values) do not vary over 107 cycles which is important especially in electromechanical transducers and memory devices. A large piezoelectric charge coefficient (d33 ~ 115pC/N) was observed for the investigated ceramics.

Controllable defects and electrical properties of nonstoichiometric Na0.5-xBi0.5+xBi2Nb2O9 high temperature piezoceramics

High temperature piezoelectric materials have attracted much attention owing to their potential applications for structural health monitoring and nondestructive evaluation in new jet engines, steam and nuclear plants. Nonstoichiometric (Na0.5-xBi0.5+x)Bi2Nb2O9 high temperature piezoceramics were prepared by a conventional solid-state sintering route. The microstructure, dielectric, DC resistivity and piezoelectric properties were investigated. Pure Aurivillius phase structure only existed in a narrow region (−0.02 ≤ x < 0.02). Moreover, the anisotropic grain morphologies were significantly restrained by increasing Bi contents. The oxygen vacancies were artificially tailored in nonstoichiometric compositions. The dynamic piezoelectricity as a function of the poling electric field was also studied and underlying physic mechanism was discussed. (Na0.48Bi0.52)Bi2Nb2O9 ceramic has the large piezoelectric coefficient (d33∼20.8pC/N), high Curie-temperature (TC∼796 °C) and low thermal aging rate (<10% @700 °C), indicating that it is a promising candidate for ultra-high temperature piezoelectric sensor applications.

Exceptionally High Piezoelectric Coefficient and Low Strain Hysteresis in Grain-Oriented (Ba, Ca)(Ti, Zr)O3 through Integrating Crystallographic Texture and Domain Engineering.

Both low strain hysteresis and high piezoelectric performance are required for practical applications in precisely controlled piezoelectric devices and systems. Unfortunately, enhanced piezoelectric properties were usually obtained with the presence of a large strain hysteresis in BaTiO3 (BT)-based piezoceramics. In this work, we propose to integrate crystallographic texturing and domain engineering strategies into BT-based ceramics to resolve this challenge. [001]c grain-oriented (Ba0.94Ca0.06)(Ti0.95Zr0.05)O3 (BCTZ) ceramics with a texture degree as high as 98.6% were synthesized by templated grain growth. A very high piezoelectric coefficient (d33) of 755 pC/N, and an extremely large piezoelectric strain coefficient (d33* = 2027 pm/V) along with an ultralow strain hysteresis (Hs) of 4.1% were simultaneously achieved in BT-based systems for the first time, which are among the best values ever reported on both lead-free and lead-based piezoceramics. The exceptionally high piezoelectric response is mainly from the reversible contribution, and can be ascribed to the piezoelectric anisotropy, the favorable domain configuration, and the formation of smaller sized domains in the BCTZ textured ceramics. This study paves a new pathway to develop lead-free piezoelectrics with both low strain hysteresis and high piezoelectric coefficient. More importantly, it represents a very exciting discovery with potential application of BT-based ceramics in high-precision piezoelectric actuators.

Optical, piezoelectric, leakage current and polarization fatigue studies of NBT-KNN ceramics near MPB

ABSTRACTLead-free (1-x)Na0.5Bi0.5TiO3-xK0.5Na0.5NbO3/(1-x)NBT-xKNN solid solutions (x = 0.05, 0.06, 0.07, 0.08) near morphotropic phase boundary (MPB) were investigated for their optical, piezoelectric, polarization fatigue and leakage current properties. Optical band gap of all the ceramics was found to be ∼3 eV. The x = 0.07 composition exhibited large piezoelectric and electromechanical coupling coefficient, small leakage current density of ∼1.04 × 10−6 A/cm2 at 40 kV/cm. The bipolar fatigue behavior carried out by the remnant polarization vs. number of cycles (up to 109). These findings confirmed the existence of MPB in x = 0.07 composition and its potentiality for memory and actuator applications.

Electronic, Elastic and Piezoelectric Properties of Two-Dimensional Group-IV Buckled Monolayers* *Supported by the National Natural Science Foundation of China under Grant No 51672208, the National Science and Technology Pillar Program during the Twelfth Five-Year Plan Period under Grant No 2012BAD47B02, the Sci-Tech Research and Development Program of Shaanxi Province under Grant Nos 2010K01-120, 2011JM6010 and 2015JM5183, the Shaanxi Provincial Department

Electronic, elastic and piezoelectric properties of two-dimensional (2D) group-IV buckled monolayers (GeSi, SnSi and SnGe) are studied by first principle calculations. According to our calculations, SnSi and SnGe are good 2D piezoelectric materials with large piezoelectric coefficients. The values of d 11 of SnSi and SnGe are 5.04 pm/V and 5.42 pm/V, respectively, which are much larger than 2D MoS2 (3.6 pm/V) and are comparable with some frequently used bulk materials (e.g., wurtzite AlN 5.1 pm/V). Charge transfer is calculated by the Löwdin analysis and we find that the piezoelectric coefficients (d 11 and d31) are highly dependent on the polarizabilities of the anions and cations in group-IV monolayers.

Influence of composition on the unipolar electric fatigue of Ba(Zr0.2Ti0.8)O3‐(Ba0.7Ca0.3)TiO3 lead‐free piezoceramics

AbstractThe lead‐free (1−x)Ba(Zr0.2Ti0.8)O3‐x(Ba0.7Ca0.3)TiO3 system is considered as promising candidate for the replacement of lead‐based piezoceramics in actuation applications, during which electric fatigue is a major concern. This issue was addressed in this work, where the unipolar fatigue resistance of three (1−x)Ba(Zr0.2Ti0.8)O3‐x(Ba0.7Ca0.3)TiO3 compositions with different crystallographic structures (rhombohedral, orthorhombic, and tetragonal) was evaluated. Strain asymmetry and development of an internal bias field were observed in all compositions. The decrease in the remanent polarization and the large signal piezoelectric coefficient after 107 unipolar cycles was found to lie between 6%‐12% and 2%‐13%, respectively. The most pronounced fatigue was observed for the orthorhombic composition, which has the largest extrinsic contribution to strain. On the other hand, the best fatigue resistance was observed for the tetragonal composition, which has a predominantly intrinsic strain response. The correlation of fatigue resistance with strain mechanism was corroborated with determination of the Rayleigh parameters and changes in the domain morphology after cycling as confirmed by piezoresponse force microscopy.

Improved electrical properties of BaTiO3 modified BiScO3-PbTiO3 ceramics with high Curie temperature

Abstract The Bi Me O 3 -PbTiO 3 ( Me = Sc 3+ , In 3+ , Yb 3+ ) systems have been predicted to have remarkable advantage in their Curie temperature in comparison with other perovskite ferroelectric materials. As one member of these options, the BiScO 3 -PbTiO 3 (BS-PT) solid solution has drawn much attention from scientists for their high Curie temperature and excellent piezoelectric coefficient. Herein, we report the improved electrical properties of BiScO 3 -PbTiO 3 ceramics modified by BaTiO 3 (0.36BiScO 3 -(0.64- x )PbTiO 3 - x BaTiO 3 ). A large piezoelectric coefficient ( d 33 ) of 350 pC/N, a high Curie temperature ( T C ) of 393 °C，a high ferroelectric phase transition temperature ( T RT ) of 196 °C and a reduced coercive field ( E C ) of 24.6 kV/cm were obtained at x = 0.1. Moreover, the structure transition, phase transition temperature and electrical properties was also studied with the content of BaTiO 3 in the large range of x = 0–0.4. A morphotropic phase boundary (MPB) was found with the composition in the range of x = 0.05–0.2. The piezoelectric coefficients exhibit good thermal stability for slightly change of d 33 * with temperature range of 30–150 °C, making it a candidate for use in high power and high temperature field.

A Game Changer: A Multifunctional Perovskite Exhibiting Giant Ferroelectricity and Narrow Bandgap with Potential Application in a Truly Monolithic Multienergy Harvester or Sensor.

An ABO3 -type perovskite solid-solution, (K0.5 Na0.5 )NbO3 (KNN) doped with 2 mol% Ba(Ni0.5 Nb0.5 )O3-δ (BNNO) is reported. Such a composition yields a much narrower bandgap (≈1.6 eV) compared to the parental composition-pure KNN-and other widely used piezoelectric and pyroelectric materials (e.g., Pb(Zr,Ti)O3 , BaTiO3 ). Meanwhile, it exhibits the same large piezoelectric coefficient as that of KNN (≈100 pC N-1 ) and a much larger pyroelectric coefficient (≈130 µC m-2 K-1 ) compared to the previously reported narrow-bandgap material (KNbO3 )1-x -BNNOx . The unique combination of these excellent ferroelectric and optical properties opens the door to the development of multisource energy harvesting or multifunctional sensing devices for the simultaneous and efficient conversion of solar, thermal, and kinetic energies into electricity in a single material. Individual and comprehensive characterizations of the optical, ferroelectric, piezoelectric, pyroelectric, and photovoltaic properties are investigated with single and coexisting energy sources. No degrading interaction between ferroelectric and photovoltaic behaviors is observed. This composition may fundamentally change the working principles of state-of-the-art hybrid energy harvesters and sensors, and thus significantly increases the unit-volume energy conversion efficiency and reliability of energy harvesters in ambient environments.

Prediction of two‐dimensional BiSb with puckered structure

Using global particle‐swarm optimization method and first‐principles calculations, we predict that the monolayer BiSb with puckered structure (p‐BiSb) enjoys lowest energy in the configurations of the single layer BiSb theoretically predicted until now. Its moderate direct band gap predicted with HSE functional indicates that it is promising for further nano‐electronic and nano‐optical devices. Our calculations also reveal that uniaxial strain is an effective way to modulate its band gap. More importantly, p‐BiSb shows relatively large piezoelectric coefficient, indicating its potential for sensors. Top and side view of the structure of p‐BiSb and relaxed‐ion polarization change under applied uniaxial strain () along the a direction of p‐BiSb.

Epitaxial ScAlN grown by molecular beam epitaxy on GaN and SiC substrates

ScxAl1-xN is a promising ultra-wide bandgap material with a variety of potential applications in electronic, optoelectronic, and acoustoelectric devices related to its large piezoelectric and spontaneous polarization coefficients. We demonstrate growth of ScxAl1-xN on GaN and SiC substrates using plasma-assisted molecular beam epitaxy with x = 0.14–0.24. For metal-rich growth conditions, mixed cubic and wurtzite phases formed, while excellent film quality was demonstrated under N-rich growth conditions at temperatures between 520 and 730 °C. An rms roughness as low as 0.7 nm and 0002 rocking curve full-width at half maximum as low as 265 arc sec were measured for a Sc0.16Al0.84 N film on GaN. To further demonstrate the quality of the ScAlN material, a high-electron-mobility transistor heterostructure with a Sc0.14Al0.86 N barrier, GaN/AlN interlayers, and a GaN buffer was grown on SiC, which showed the presence of a two-dimensional electron gas with a sheet charge density of 3.4 × 1013 cm−2 and a Hall mobility of 910 cm2/V·s, resulting in a low sheet resistance of 213 Ω/◻.