Value Of Piezoelectric Coefficient Research Articles

Lithium-modified (K0.5Na0.5)NbO3–BiAlO3 lead-free piezoelectric ceramics with high Curie temperature

Lead-free piezoelectric ceramics based on the perovskite solid solution 0.995(K0.5Na0.5)1−xLixNbO3–0.005BiAlO3 were prepared using conventional solid-state sintering techniques. According to the analysis of X-ray diffraction patterns, a pure perovskite phase structure could be achieved in the studied composition range of 0≤x≤0.08. As the lithium content increased, the crystal structure gradually transitioned from orthorhombic to tetragonal symmetry. Furthermore, an orthorhombic–tetragonal phase boundary could be observed in ceramics with the compositions of 0.03≤x≤0.05. The ceramics with compositions close to the orthorhombic–tetragonal phase boundary exhibited enhanced piezoelectric activity, possessing the largest values of piezoelectric constant d33, and planar and thickness electromechanical coupling coefficients, of 182 pC/N, 0.375, and 0.460, respectively. Additionally, it was found that these ceramics with excellent piezoelectric properties also possessed a high Curie temperature (~ 450°C), indicating that they would be suitable for application in elevated-temperature piezoelectric devices.

Inter-relations of domain orientations and piezoelectric properties in composites based on relaxor-ferroelectric single crystals

ABSTRACTThis paper presents results on a detailed comparative study of 2–2 relaxor-ferroelectric single crystal / polymer composites. Examples of the hydrostatic piezoelectric performance are discussed for 2–2 composites based on [011]-poled Mn-modified 0.26Pb(In1/2Nb1/2)·O3−0.42Pb(Mg1/3Nb2/3)O3−0.32PbTiO3 single crystals at a molar Mn concentration in the range of 1–5 mol. %. The high piezoelectric activity of these single crystals and rotations of the main crystallographic axes in the single-crystal layers of the composite lead to large values of hydrostatic piezoelectric coefficients , and , squared figure of merit , and electromechanical coupling factor . A rotation mode that leads to a weakening the piezoelectric activity related to the piezoelectric coefficient d32 < 0 is important to achieve composites with a range of large hydrostatic parameters, e.g., ≈ (300–350) pC / N, ∼ 100 mV·m / N, ≈ (21–23) C / m2, ∼ (24–30)·10−12 Pa−1, and ≈ 0.30. In contrast to , higher values of ∼ 10−10 Pa−1 are achieved due to the longitudinal piezoelectric effect. The results obtained in this piezoelectric composite system are interpreted by taking into account the orientation of 71° ferroelectric domains in the single-crystal layers and provide a route to form novel high-performance piezoelectric composites.

Piezoelectric and dielectric properties of 0.995K0.48Na0.48Li0.04Nb(1−x)SbxO3–0.005BiAlO3 lead-free piezoelectric ceramics

Lead-free 0.995K0.48Na0.48Li0.04Nb(1−x)SbxO3–0.005BiAlO3 piezoelectric ceramics with perovskite structure were designed and prepared with conventional ceramic fabrication techniques. The phase transitions of the ceramics were determined by X-ray diffraction patterns and the temperature dependence of dielectric properties. The ceramics possessed an orthorhombic–tetragonal phase boundary with x=0 and exhibited the coexistence of rhombohedral–orthorhombic and orthorhombic–tetragonal phase boundaries at around room temperature, with 0.02≤x≤0.03. Upon further increasing the Sb content, the crystal structure transformed to the rhombohedral-tetragonal phase coexistence in the composition range of 0.04≤x≤0.05. Next, the phase structure turned to a sole rhombohedral symmetry with x≥0.06. A clearly enhanced piezoelectric activity was demonstrated for the ceramic with the rhombohedral-tetragonal phase boundary composition x=0.05, where the values of piezoelectric constant d33, planar and thickness electromechanical coupling coefficients reached 205 pC/N, 0.360 and 0.437, respectively.

Effect of Lanthanum Substitution on the Structural, dielectric, Ferroelectric and Piezoelectric Properties of Mechanically Activated PZt Electroceramics

Different compositions of (Pb1-xLax) (Zr0.60Ti0.40)O3 (abbreviated as PLZT x/60/40; x=0, 0.07, 0.08 and 0.10) ceramics were prepared by a combinatorial approach by high energy mechano-chemical ball milling and cold isostatic pressing (CIP). X-ray diffraction patterns and transmission as well as scanning electron microscope were used for the micro-structural and morphological studies. The average particle size of PLZT milled powders was measured from the TEM images and was found to be in the nm range.XRD patterns of the sintered PLZT x/60/40 ceramics confirm the perovskite phase formation after heat treatment. SEM of sintered PLZT x/60/40 ceramics show a close packed dense structure. PLZT 8/60/40 ceramics show the fine grains (~1.3 µm) with density ~97 per cent. Dielectric constant and loss were measured as a function of temperature. PLZT 8/60/40 ceramics shows the highest value of room temperature dielectric constant ~2480 at 1 kHz. Ferroelectric studies were done with the help of polarisation (P-E) and strain (S-E) vs. electric field measurements. PLZT 8/60/40 ceramics shows the maximum value of remnant polarisation (~36 µC/cm2) and strain (~0.27 per cent), respectively. PLZT x/60/40 ceramic samples were poled at optimized poling conditions. The measured values of piezoelectric charge coefficient (d33) and electromechanical coupling factor (kp) of PLZT 8/60/40 ceramics were found to be, ~690 pC/N and ~71 per cent, respectively.

Phase Structure, Microstructure and Electrical Properties of BCZT Ceramics Prepared by Seed-Induced Method

The effect of particle sizes of CaZrO3 (CZ) nanocrystal on the phase structure, microstructure and electrical properties of Ba0.85Ca0.15Zr0.10Ti0.90O3 (BCZT) was studied. The CaCO3 and ZrO2 were used as starting materials for CaZrO3 (CZ) seeds synthesized by the molten-salt method. The results were found that the CZ powder has a pure perovskite with the particle size about 370 to 460 nm. Then the CZ nanocrystals were mixed with the metal oxides BaCO3, CaCO3, ZrO2 and TiO2 by mixed oxide method. The phase structure, microstructure and electrical properties of BCZT ceramic were investigated as a function of particle size and concentration of CZ. The results indicated that all samples showed pure perovskite phase. The highest values of density, grain size, dielectric constant (εr) and piezoelectric coefficient (d33) were 5.50 g/cm3, 10.95 μm, 2992 and 446 pC/N, respectively which obtained at the CZ seed size 459 nm.

Microwave sintering of fine grained PLZT 8/60/40 ceramics prepared via high energy mechanical milling

Fine powders of lanthanum modified (Pb0.92La0.08)(Zr0.60Ti0.40)O3 (PLZT 8/60/40) were processed by high energy mechanical ball milling. The ceramic pellets from these powders were sintered by using microwave sintering. Microwave processed ceramics were further investigated for their sintering behaviour, microstructure, dielectric and piezoelectric properties. The XRD pattern of PLZT shows a single phase formation except for the ceramics sintered at 1200°C. Higher density and more uniform grain distribution were found for PLZT ceramics, microwave sintered at 1150°C, in spite of having much shorter sintering time. As a result, comparable dielectric and piezoelectric properties were obtained for microwave sinterd PLZT ceramics. These show the grain size ∼1.2μm, and the highest relative density ∼99.46%. The dielectric constant for the unpoled PLZT ceramics was found to be ∼2100. The piezoelectric charge (d33) and electromechanical coupling coefficient (kp) value for the PLZT ceramics were found to be, ∼574 pC/N and ∼67% respectively.

Study of xCo0.8Ni0.2Fe2O4+(1−x) Pb0.99625 La0.0025Zr0.55Ti0.45O3 magnetoelectric composites

We are reporting here, the studies of the structural, dielectric, ferroelectric and magnetic properties of magnetoelectric composites of La modified lead zirconate titanate (PLZT) and Ni modified cobalt ferrite (CNFO) with compositional formula xCo0.8Ni0.2Fe2O4+(1−x) Pb0.99625La0.0025Zr0.55Ti0.45O3 (x=0.00, 0.05, 0.10, 0.15 and 1.00 by weight) prepared by the solid state reaction method. Coexistence of both the phases in composites was confirmed by X-Ray diffraction technique. The microstructure and average grain size were determined from Scanning Electron Micrograph (SEM) in backscattered mode. Both the phases could be observed clearly. The variations of dielectric properties with frequency and temperature were also studied. P–E and M–H hysteresis measurements were carried. Magnetoelectric coupling (ME) coefficient for samples with x=0.05 and 0.10 were measured as a function of DC magnetic field. Maximum value of ME coefficient (1.2mV/cmOe) and piezoelectric coefficient (96 pC/N) for x=0.05 were observed.

Remarkable hydrostatic piezoelectric response of novel 2–0–2 composites

ABSTRACTThis is the first study of the significant influence of the 0–3 ceramic / polymer layer on the hydrostatic piezoelectric parameters of novel 2–0–2 relaxor-ferroelectric single crystal / ferroelectric ceramic / polymer composites. Examples of the performance of two 2–0–2 composites based on domain-engineered single crystals are analysed by taking into account the elastic anisotropy of the 0–3 ceramic/polymer layers with changes in the volume fraction of ceramic inclusions and their aspect ratio. The unique feature of the hydrostatic properties of the studied 2–0–2 composites consists in their large values of piezoelectric coefficients $d*h$ ≈ 1 nC/N and $e*h$ ≈ 20 C/m2, squared figure of merit $d*h$$g*h$∼ 10−10 Pa−1, and electromechanical coupling factor $k*h$ ≈ 0.7.

Structural, Dielectric and Magnetoelectric Properties of x Co0.8Ni0.2 Fe2O4 + (1-x) PbZr0.55Ti0.45O3 Composites

In this paper, we are reporting structural, dielectric, ferroelectric and magnetic properties of polycrystalline composites (ferrite and ferroelectric) of PZT (PbZr0.55Ti0.45O3) + CNFO (Co0.8Ni0.2Fe2O4). The sample with composition x CNFO + (1-x) PZT (x = 0.00, 0.05, 0.10, 0.15 and 1.00) were prepared using the solid state double sintering method. Here the ratio x: (1-x) of two components is by weight. X-ray diffraction (XRD) studies show that lattice constant and tetragonality decreases with increasing ferrite content. Dielectric constant was found to decrease with increase in amount of CNFO. The value of tangent loss (tanδ) was reasonably low (< 0.04) for all the samples. Ferroelectric and ferrimagnetic behavior was confirmed by observing P-E and M-H hysteresis loop, respectively. The room temperature magnetoelectric coupling coefficient (α = dE/dH) was measured as a function of applied DC magnetic field. The value of α was observed to be maximum (855 μV/(cm.Oe)) at DC magnetic field of 1.7 kOe for sample with 5% CNFO. Value of piezoelectric coefficient ‘d33’ decreases from 133 to 60 pC/N.

Growth, structure and optical properties of Tl4HgBr6 single crystals

Tl4HgBr6 single crystals were grown using solution-fusion method. The crystal structure of the ternary bromide was refined. Tl4HgBr6 crystallizes in the non-centrosymmetric space group P4nc with the lattice parameters a=8.9539(8)Å and c=8.7884(8)Å and it is isostructural to the Tl4HgI6 compound. The non-centrosymmetric structure of the Tl4HgBr6 compound was also confirmed by the existence of a modest second harmonic generation effect (0.4–0.5pm/V) and by the value of piezoelectric coefficient (0.9pm/V). The electronic structure of Tl4HgBr6 was explored using X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES). In particular, for the Tl4HgBr6 crystal, we have measured XPS core-level and valence-band spectra for both pristine and Ar+ ion-bombarded surfaces. The XPS data reveal low hygroscopicity of Tl4HgBr6, the property that is very important when handling this material in optoelectronic devices working at ambient conditions. The present XPS data indicate that the Tl4HgBr6 single crystal surface is rather sensitive with respect to Ar+ ion-bombardment: such a treatment reduces significantly mercury content in the topmost surface layers. Comparison on a common energy scale of the XPS valence-band spectrum of Tl4HgBr6 and the XE Br Kβ2 band, representing peculiarities of the energy distribution of the Br 4p states, reveals that the main contribution of the valence Br p states occurs in the upper portion of the valence band, with also their significant contributions in other valence band regions. The measurements of spectral distribution of the absorption coefficient indicate that the Tl4HgBr6 compound is a semiconductor with the bandgap energy value of 2.43eV at 300K, and the bandgap energy increases up to 2.48eV when temperature decreases to 100K.

Lead-free piezoelectric K0.5Bi0.5TiO3–Bi(Mg0.5Ti0.5)O3 ceramics with depolarisation temperatures up to ~220 °C

The properties of K0.5Bi0.5TiO3-rich ceramic solid solutions in the system (1 − x)K0.5Bi0.5TiO3–xBi(Mg0.5Ti0.5)O3 are reported. The highest values of piezoelectric charge coefficient, d33, and field-induced strains are found in compositions located close to a compositional boundary between single-phase tetragonal and mixed tetragonal + cubic perovskite phases. Maximum d33 values were ~150 pC/N for x = 0.03, with positive strains of ~0.25 %; the x = 0.04 composition had a d33 ~ 133 pC/N and strain of 0.35 % (bipolar electric field, 50 kV/cm, 1 Hz). Depolarisation temperature Td is an important selection criterion for any lead-free piezoelectric for actuator or sensor applications. A Td of ~220 °C for x = 0.03 is ~100 °C higher than for the widely reported Na0.5Bi0.5TiO3–BaTiO3 system, yet d33 values and strains are similar, suggesting the new material is worthy of further attention as a lead-free piezoceramic for elevated temperature applications.

Microstructure and piezoelectric properties of c-axis ScAlN films on the Y-128° LiNbO3 substrate

Abstract Highly c-axis preferred orientation ScAlN films were deposited on Y-128° lithium niobate using the co-sputtering technique. The substitution of Sc atoms at Al positions causes a lattice distortion and induces a large piezoelectric response. X-ray diffraction patterns indicated that most of the films showed (002) peaks and the best crystallinity appeared at the Sc content of 9.0 at.%. The cross-section of TEM results showed that the higher c-axis orientation columnar structure formed as the film thickness increased, and the structure transforms from wurtzite to cubical structure from the nano-beam diffraction analysis. Then the piezoelectric coefficient would be enhanced obviously at the Sc content of 18.1 at.% and the value is nearly two times larger than pure AlN. After rapid thermal annealing treatment, the crystal quality could be improved and the highest value of piezoelectric coefficient was achieved at 18.26 pC/N.

Combined contributions of phase structure and preferred orientation on the piezoelectric properties of polycrystalline (Pb0.94La0.04) Zr0.6Ti0.4O3 thin films

Polycrystalline (Pb0.94La0.04) Zr0.6Ti0.4O3 thin films were fabricated by a sol–gel method on the Pt (111)/Ti/SiO2/Si (100) substrates. Results from X-ray diffraction reveal that a strain-induced low-asymmetry monoclinic (MB) phase exists in all the films as compared with its powder counterpart. Also, films exhibit a simple trend of pyrolysis-sensitive (100)-orient growth. Good piezoelectric longitudinal coefficient values are obtained in the films where a maximum around 130pm/V is reached for the film pyrolyzing at 425°C. These findings suggest that combined contributions of monoclinic phase and (100)-preferred orientation type as well as good surface quality will account for excellent piezoelectric properties for ferroelectric films.

Effect of Ti on the properties of (KxNa1−x)NbO3 based lead-free ceramics

The effect of modifying lead-free alkaline niobate based piezoelectric ceramics with different amounts of Ti has been investigated. Thermal studies using a dilatometer show that increasing Ti amount leads to decreasing sintering temperature by approximately 11.7°C for every 1mol% of the dopant added. Chemical analysis on the ceramics reveals that the measured amounts of the alkali elements are slightly lower while small amounts of Zr were introduced to the ceramic through the milling process. Microstructural analysis shows that that the average grain size decreases with increasing dopant amount and that new, smaller sized grains are formed in the presence of Ti. Two-phase orthorhombic–tetragonal diffraction patterns are observed using synchrotron X-ray diffraction while the analysis using Rietveld refinement shows that the fraction of the tetragonal phase in the two-phase patterns increase with increasing Ti content. The dielectric, piezoelectric coefficient values and ferroelectric properties of the ceramics decrease with increasing Ti amount. The current density values in the samples increase by up to 5 orders of magnitude when more than 0.5mol% of the dopant is added.

Piezoelectric properties of rhombohedral ferroelectric materials with phase transition

The temporal evolution of domain structure and its piezoelectric behavior of ferroelectric material BaTiO 3 during the transition process from rhombohedral to tetragonal phase under an applied electric field have been studied by employing Landau–Ginzburg theory and the phase-field method. The results obtained show that, during the transformation process, the intermediate phase was monoclinic MA phase, and several peak values of piezoelectric coefficient appeared at the stage where obvious change of domain pattern occurred. In addition, by comparing the cases of applied electric field with different frequencies, it was found that the maximum piezoelectric coefficient obtained decreased with increasing frequency value. These results are of great significance in tuning the properties of engineering domains in ferroelectrics, and could provide more fundamentals to the design of ferroelectric devices.

Robust Aligned Carbon Nanotube Tape with Excellent Piezoelectric Properties

We report a highly aligned multiwalled carbon nanotube (MWCNT) tape with a P(VDF-TrFE) matrix that is mechanically robust and has excellent piezoelectric properties for sensor applications, including, but not limited to vibration gyroscopes and accelerometers. The tapes were tested for piezoelectric response via hysteresis measurements and d33 measurements. It was found that 10 weight percent P(VDF-TrFE) in a solution of DMSO resulted in increased values of dielectric constant, piezoelectric coefficient and mechanical properties. The d33 value for the CNT/P(VDF-TrFE) was 70 pm/V, which is approximately twice that for pure P(VDF-TrFE) film. Adding 10 weight percent BaTiO3 nanoparticles (100nm) increased the piezoelectric d33 value to 81 pm/V. These results are attributed to Maxwell-Wagner-Sillars polarization. This material has a tensile strength of 120 MPa and a Young’s modulus of 17.8 GPa. Keywords: Barium titanate, carbon nanotube, piezoelectricity, P(VDF-TrFE), sensors, strength.

Size Effect of Piezoelectricity in ZnO Nanowires: A First-Principles Study

Piezoelectric properties of ZnO nanowires orientated along [0001] are investigated via density functional theory (DFT). A new method to calculate the volume of nanowires was proposed, which is crucial to the value of piezoelectric coefficients. Results show that the axial effective piezoelectric coefficients are 29.99 Cm-2, 25.93 Cm-2, 22.82 Cm-2 for ZnO nanowires with diameters of about 0.6 nm, 1.2 nm, 1.8 nm, which are considerably larger than that of the bulk (20.19Cm-2). It is found that the change in volume during the strain played a dominated role in size effects. This work helps to gain a deeper understanding of the piezoelectric size effects in ZnO nanowires.

Thin-film piezoelectric bimorph actuators with increased thickness using double Pb[Zr,Ti]O3 layers

We studied the effects of increasing the thickness of bimorph structures containing double layers of Pb(Zr,Ti)O3 (PZT) thin films. Thick PZT films allow high-voltage application (e.g. in terms of coercive electric field and breakdown voltage) and large generative force, which are effective in microelectromechanical systems (MEMS) applications. Improvement of the deposition conditions and electrode structures facilitates the fabrication of the thin-film PZT/PZT bimorph structure. The PZT/PZT bimorph with a total thickness of 5.8 µm, deposited using a radio-frequency (RF) magnetron sputtering system is much thicker than conventional bimorph structures. The characteristics of the two piezoelectric layers were similar to each other and revealed good electric and ferroelectric characteristics with a remanent polarization of 20 µC cm−2 and a coercive electric field of 50 kV cm−1. PZT/PZT bimorph cantilevers were fabricated in order to evaluate their characteristics for actuator applications. The residual stress of the bimorph cantilever was reduced by an annealing process. The vibration test on the fabricated bimorph cantilevers during electrical voltage application revealed a twice as large displacement as compared with a single layer actuation, and the piezoelectric coefficient value d31 was estimated to be −61 pm V−1, which is better than the value of conventional PZT/PZT bimorph cantilevers (−13 pm V−1). It was also shown that the influence of the temperature change is much less than that in unimorph structures with similar dimensions. The evaluated results demonstrate that the PZT/PZT bimorph structures are effective as MEMS devices.

Investigation on the phase transition behavior and electrical properties of textured Lix(K0.48Na0.52)1−xNbO3 piezoelectric ceramics

Lead-free Lix(K0.48Na0.52)1−xNbO3 (KNN–xLi) ceramics were successfully prepared by the tape casting method and solid-state reaction. The effects of Li content on phase transition, microstructure and electrical properties were investigated. XRD results show strong preferred orientation, indicating the presence of textured structure in the samples. With increasing Li content, the Currie Temperature shifts to higher temperature while the phase transition temperature between orthorhombic and tetragonal phases shifts to lower temperature. The sample with x=0.05 is determined to contain two perovskite phases with orthorhombic and tetragonal structures at room temperature, respectively, and exhibits the maximum values of piezoelectric coefficient of 286 pC/N and planar electromechanical coupling factor of 0.45.

Poling electric field dependent domain switching and piezoelectric properties of mechanically activated (Pb0.92La0.08)(Zr0.60Ti0.40)O3 ceramics

(Pb0.92La0.08)(Zr0.60Ti0.40)O3 (PLZT 8/60/40) ceramics were prepared via a combinatorial approach of high energy mechanical ball milling (mechanical activation), followed by cold isostatic pressing. Electrical properties of the piezoelectric ceramics are greatly influenced by the poling conditions (poling electric field, poling time and poling temperature). In this present study, the effect of the poling electric fields on the piezoelectric properties of PLZT 8/60/40 ceramics was investigated. It is a common practice to subject piezoelectric ceramics to electric fields well beyond their coercive fields, in order to pole them but here the measured values of piezoelectric (d33 and g33) and electromechanical coupling coefficients (kp, k33 and k31) at different poling fields show that a ferroelectric material can be poled at ~5 kV/cm (<0.5 Ec), far below the coercive field without compromising the induced high piezoelectricity. The results were discussed with the help of polarization, current and strain versus electric field curves.