Longitudinal Piezoelectric Coefficient Research Articles

Simultaneously enhanced piezoelectric response and piezoelectric voltage coefficient in textured KNN‐based ceramics

Abstract<001> ‐textured 0.99(K0.49Na0.49Li0.02)(Nb0.97‐xSb0.03Tax)O3‐0.01CaZrO3 [abbreviated as 0.99KNLN0.97‐xSTx‐0.01CZ, x = 0.03, 0.07, 0.10, 0.15, 0.20, 0.25] ceramics were prepared by templated grain growth (TGG) method and a two‐step sintering process. Giant longitudinal piezoelectric coefficient d33 (391 pC/N) and piezoelectric strain coefficient d33* (630 pm/V under an AC E‐field of 20 kV/cm) can be obtained in the textured ceramics with x = 0.25. All textured ceramics display superior kp (>54%) and g33 (>23 × 10−3 Vm/N) which are in an order of magnitude with PZT ceramics. The maximum value of kp (~63.3%) obtained in textured ceramics with x = 0.15 is higher than that of famous textured LF4 ceramics. Excellent comprehensive properties suggest that <001> ‐textured 0.99KNLN0.97‐xSTx‐0.01CZ ceramics are promising candidates in the field of lead‐free piezoelectric materials.

Piezoelectric Tensor of Collagen Fibrils Determined at the Nanoscale.

Piezoelectric properties of rat tail tendons, sectioned at angles of 0, 59, and 90° relative to the plane orthogonal to the major axis, were measured using piezoresponse force microscopy. The piezoelectric tensor at the length scale of an individual fibril was determined from angle-dependent in-plane and out-of-plane piezoelectric measurements. The longitudinal piezoelectric coefficient for individual fibrils at the nanoscale was found to be roughly an order of magnitude greater than that reported for macroscopic measurements of tendon, the low response of which stems from the presence of oppositely oriented fibrils, as confirmed here.

Thickness‐dependent domain wall reorientation in 70/30 lead magnesium niobate‐ lead titanate thin films

AbstractContinued reduction in length scales associated with many ferroelectric film‐based technologies is contingent on retaining the functional properties as the film thickness is reduced. Epitaxial and polycrystalline lead magnesium niobate‐lead titanate (70PMN‐30PT) thin films were studied over the thickness range of 100‐350 nm for the relative contributions to property thickness dependence from interfacial and grain‐boundary low permittivity layers. Epitaxial PMN‐PT films were grown on SrRuO3/(001)SrTiO3, while polycrystalline films with {001}‐Lotgering factors >0.96 were grown on Pt/TiO2/SiO2/Si substrates via chemical solution deposition. Both film types exhibited similar relative permittivities of ~300 at high fields at all measured thicknesses with highly crystalline electrode/dielectric interfaces. These results, with the DC‐biased and temperature‐dependent dielectric characterization, suggest irreversible domain wall mobility is the major contributor to the overall dielectric response and its thickness dependence. In epitaxial films, the irreversible Rayleigh coefficients reduced 85% upon decreasing thickness from 350 to 100 nm. The temperature at which a peak in the relative permittivity is observed was the only measured small signal quantity which was more thickness‐dependent in polycrystalline than epitaxial films. This is attributed to the relaxor nature present in the films, potentially stabilized by defect concentrations, and/or chemical inhomogeneity. Finally, the effective interfacial layers are found to contribute to the measured thickness dependence in the longitudinal piezoelectric coefficient.

Strongly Enhanced Piezoelectric Response in Lead Zirconate Titanate Films with Vertically Aligned Columnar Grains.

Pb(Zr0.52Ti0.48)O3 (PZT) films with (001) orientation were deposited on Pt(111)/Ti/SiO2/Si(100) substrates using pulsed laser deposition. Variation of the laser pulse rate during the deposition of the PZT films was found to play a key role in the control of the microstructure and to change strongly the piezoelectric response of the thin film. The film deposited at low pulse rate has a denser columnar microstructure, which improves the transverse piezoelectric coefficient (d31f) and ferroelectric remanent polarization (Pr), whereas the less densely packed columnar grains in the film deposited at high pulse rates give rise to a significantly higher longitudinal piezoelectric coefficient (d33f) value. The effect of film thickness on the ferroelectric and piezoelectric properties of the PZT films was also investigated. With increasing film thickness, the grain column diameter gradually increases, and also the average Pr and d33f values become larger. The largest piezoelectric coefficient of d33f = 408 pm V–1 was found for a 4-μm film thickness. From a series of films in the thickness range 0.5–5 μm, the z-position dependence of the piezoelectric coefficient could be deduced. A local maximum value of 600 pm V–1 was deduced in the 3.5–4.5 μm section of the thickest films. The dependence of the film properties on film thickness is attributed to the decreasing effect of the clamping constraint imposed by the substrate and the increasing spatial separation between the grains with increasing film thickness.

Effects of slurry composition on the properties of 3-1 type porous PZT ceramics prepared by ionotropic gelation

In this study, 3-1 type lead zirconate titanate (PZT) ceramics with one-dimensional pore channels were produced by ionotropic gelation process of alginate/PZT suspensions. By increasing the sodium alginate concentration from 1.0wt% to 3.0wt%, the alginate/PZT suspensions turned from Newtonian to non-Newtonian behavior with substantial increase in apparent viscosity. Accordingly, 3-1 type PZT ceramics with porosity decreasing from 56.78% to 41.44% were obtained, while the pore size distribution became non-uniform gradually. Based on the structural features, the 3-1 type PZT ceramics possessed much higher relative permittivity (εr) than that of 3-0 or 3-3 type PZT ceramics with similar porosities. Increase in the porosity led to a moderate decline in the longitudinal piezoelectric strain coefficient (d33), a reduction in the dielectric loss factor (tan δ), and a high value of hydrostatic strain coefficient (dh). As a result, the 3-1 type PZT ceramics possessed a maximal hydrostatic figure of merit (HFOM) value of 5597×10–15Pa−1 when the porosity was 56.78%, which may be of help for low frequency hydrophones applications.

Modelling and fabrication of porous sandwich layer barium titanate with improved piezoelectric energy harvesting figures of merit

This paper demonstrates that porous ‘sandwich’ structures can provide an effective route for the design and optimisation of piezoelectric materials for energy harvesting applications, which is becoming an increasingly important technology for self-powered wireless networks and sensors. A numerical model is presented that accounts for the complex poling distribution throughout a layered ferroelectric and helps to develop a detailed understanding of the relationship between the geometry of the porous structure and the poling characteristics of porous ferroelectric materials, with good agreement with experimental data. Novel layered barium titanate ceramics were fabricated whereby dense outer layers surround a highly porous sandwich layer, and for specific layer geometries an unusual condition was achieved where the longitudinal piezoelectric strain coefficients (d33) increased as the thickness of the porous layer and total porosity level of the layered structure increased. The permittivity (ε33T) decreased with increasing thickness and increasing porosity level of the porous layer due to the presence of a low permittivity air phase. These two factors in combination led to an increase in the longitudinal energy harvesting figure of merit, d332/ε33T, for the layered structure, with a maximum of 3.74 pm2/N when the relative thickness of the porous layer was 0.52 and the porosity within this layer was ∼60 vol%. This harvesting performance of these novel structures is much larger than both dense barium titanate (1.40 pm2/N) and barium titanate with randomly distributed porosity at the same 60% volume fraction (2.75 pm2/N).

Declamped Piezoelectric Coefficients in Patterned 70/30 Lead Magnesium Niobate–Lead Titanate Thin Films

Lateral subdivision of blanket piezoelectric thin films increases the functional properties through both increased domain wall mobility and declamping of the intrinsic response. This work presents the local effects of substrate declamping on the piezoelectric coefficient d33,f of 300 nm thick, rhombohedral, {001}‐oriented lead magnesium niobate–lead titanate thin films at the 70/30 composition (70PMN–30PT). Films grown by chemical solution deposition on platinized Si substrates are patterned into strip structures ranging from 0.75 to 9 µm in width. The longitudinal piezoelectric coefficient, d33,f, is interrogated as a function of position across the patterned structures by three approaches: finite element modeling, piezoresponse force microscopy, and nanoprobe synchrotron X‐ray diffraction. It is found that d33,f increases from the clamped value of 40–50 to ≈160 pm V−1 at the free sidewall under 200 kV cm−1 excitation. The sidewalls partially declamp the piezoelectric response 500–600 nm into the patterned structure, raising the piezoelectric response at the center of features with lateral dimensions less than 1 µm (3:1 width to thickness aspect ratio). The normalized data from all three methods are in excellent agreement, with quantitative differences providing insight to the field dependence of the piezoelectric coefficient and its declamping behavior.

Controllable piezoelectricity of Pb(Zr0.2Ti0.8)O3 film via in situ misfit strain

The tetragonality (c/a) of a PbZr0.2Ti0.8O3 (PZT) thin film on La0.7Sr0.3MnO3/ 0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 (PMN-PT) substrates was controlled by applying an electric field on the PMN-PT substrate. The piezoelectric response of the PZT thin film under various biaxial strains was observed using time-resolved micro X-ray diffraction. The longitudinal piezoelectric coefficient (d33) was reduced from 29.5 to 14.9 pm/V when the c/a ratio of the PZT film slightly changed from 1.051 to 1.056. Our results demonstrate that the tetragonality of the PZT thin film plays a critical role in determining d33, and in situ strain engineering using electromechanical substrate is useful in excluding the extrinsic effect resulting from the variation in the film thickness or the interface between substrate.

Control of Tetragonal Distortion and Ferroelectricity in Bi(Zn1/2Ti1/2)O3-Based Lead-Free Ferroelectric Thin Films

Lead-free ferroelectric materials with superior property have been demanded, yet a few lead-free ferroelectrics such as alkali-based (K,Na)NbO3 family and bismath-based (Bi,Na)TiO3 family have been reported. Pb(Zr,Ti)O3[PZT] is one of very famous ferroelectric because their ferroelectric and piezoelectric properties can be controlled by their composition and domain structure. And almost of all for application use, PZT having tetragonal and morphotropic phase boundary[MPB] composition have been used. From a view point of material design in PZT case, mother material of tetragonal PbTiO3 is very important for designing MPB. However, it is know that there are only BaTiO3 and (Bi,K)TiO3 in the field of tetragonal perovskite materials. Novel lead-free tetragonal ferroelectric materials are really wanted. Recently, novel metastable phase materials prepared by high pressure synthesis have been reported. Among them, BiCoO3 1 and Bi(Zn0.5Ti0.5)O3 2 are promising ferroelectric materials due to their high tetragonality, c/a, of over 1.2. Large spontaneous polarization is expected by first principal calculation. BiCoO3 is a one of multiferroic, but unfortunately it is very leaky because of containing Co3+(d 6). On the other hand, Bi(Zn0.5Ti0.5)O3 is constructed by only d 0 and d 10 ions. Unfortunately, nobody reported their ferroelectricity. We can expect that leakage property will be better than that of BiCoO3. Therefore, we have focused on Bi(Zn0.5Ti0.5)O3 and prepare novel ferroelectric materials. Epitaxial Bi(Zn0.5Ti0.5)O3-BiFeO3 thin films with about 300 nm thickness were grown at 700oC on (100)cSrRuO3//(100)SrTiO3 by pulsed metalorganic chemical vapor deposition using Bi[(CH3)2(2-(CH3)2NCH2C6H4)] (Tosoh Co. Ltd), Zn(C14H25O2)2, Ti(O∙i-C3H7)4, Fe(C2H5C5H4)2 and oxygen gas as the source materials. SrRuO3 films were grown by RF magnetron sputtering method. Film thickness and composition were confirmed by surface profilometry and X-ray fluorescence (XRF) calibrated using standard samples. Crystal structure of the deposited films was characterized by X-ray diffraction (XRD) analysis using a four-axis diffractometer with CuKa radiation. Atomic microstructures of the films were observed by high angle annular dark field scanning transmission electron microscopy (HAADF-STEM). Pt/[Bi(Zn1/2Ti1/2)O3- BiFeO3]/SrRuO3 capacitor structure was used for the electrical measurements after making circular Pt top electrodes of 100 mm in diameter, which were deposited by e-beam evaporation. Piezoresponse mappings and longitudinal piezoelectric coefficient (d 33) was measured using piezoresponse force microscopy. High resolution Advanced X-ray reciprocal space mapping leads us to know all diffractions from the films, suggesting that crystal structure and domain structure could be investigated easily. This mapping reveals d-spacing information along both the substrate surface normal and off-normal directions. It is observed that all diffraction peaks from the films can be identified to tetragonal P4mm symmetry as same as Bi(Zn1/2Ti1/2)O3, and a single perovskite phase is achieved to fabricate. The out-of-plane (c-axis) and in-plane (a-axis) lattice parameters calculated from diffractions are 0.465 nm and 0.381 nm, respectively, resulting in a giant tetragonal distortion of (c/a)-1 = 22%. This value is 3.5 times larger than the 6.3% of PbTiO3. In addition, this [(c/a)-1] is larger than the reported one for pure Bi(Zn1/2Ti1/2)O3, [(c/a)-1] = 21%. Similar enlargement of the [(c/a)-1] by the substitution with BiFeO3 has been reported in PbTiO3-BiFeO3, even if the substituted BiFeO3 has rhombohedral symmetry. We have also conducted cross sectional high resolution HAADF-STEM for visualization of the crystal structure directly. The “90o domain boundary” has a 51o/39o angle due to the large tetragonality, which is in good agreement with 50.7o/40.3 o value based on the crystal structure information obtained by XRD measurement. Z-contrast image to perovskite unit cell shows that the B-site ions are also displaced along [001] significantly away from the center. There are in good agreement with structure analysis of the Bi(Zn1/2Ti1/2)O3 prepared by high pressure synthesis. In addition, as XRD results showed no super lattice peaks, B-site cations in perovskite are not ordered. These results clearly indicate that this material is characterized as displacive-type ferroelectric, and unusual angle of the 90o domain is originated from large tetragonal distortion. We will also perform to measure ferroelectricity for discussing relationship between ferroelectricity/piezoelectricity and tetragonality in these materials. 1A. A. Belik, S. Iikubo, K. Kodama, N. Igawa, S. Shamoto, S. Niitaka, M. Azuma, Y. Shimakawa, M. Takano, F. Izumi, and E. Takayama-Muromachi, Chem. Mater. 18 (2006) 798. 2M. R. Suchomel, A. M. Fogg, M. Allix, H. Niu, J. B. Claridge, M. J. Ro sseinsky, Chem. Mater. 18 (2006) 4987.

Low temperature aluminum nitride thin films for sensory applications

A low-temperature sputter deposition process for the synthesis of aluminum nitride (AlN) thin films that is attractive for applications with a limited temperature budget is presented. Influence of the reactive gas concentration, plasma treatment of the nucleation surface and film thickness on the microstructural, piezoelectric and dielectric properties of AlN is investigated. An improved crystal quality with respect to the increased film thickness was observed; where full width at half maximum (FWHM) of the AlN films decreased from 2.88 ± 0.16° down to 1.25 ± 0.07° and the effective longitudinal piezoelectric coefficient (d33,f) increased from 2.30 ± 0.32 pm/V up to 5.57 ± 0.34 pm/V for film thicknesses in the range of 30 nm to 2 μm. Dielectric loss angle (tan δ) decreased from 0.626% ± 0.005% to 0.025% ± 0.011% for the same thickness range. The average relative permittivity (εr) was calculated as 10.4 ± 0.05. An almost constant transversal piezoelectric coefficient (|e31,f|) of 1.39 ± 0.01 C/m2 was measured for samples in the range of 0.5 μm to 2 μm. Transmission electron microscopy (TEM) investigations performed on thin (100 nm) and thick (1.6 μm) films revealed an (002) oriented AlN nucleation and growth starting directly from the AlN-Pt interface independent of the film thickness and exhibit comparable quality with the state-of-the-art AlN thin films sputtered at much higher substrate temperatures.

Intrinsic orientation effect on the piezoelectric response of multi-domain 0.26Pb(In1/2Nb1/2)O3–0.46Pb(Mg1/3Nb2/3)O3–0.28PbTiO3 crystals

The crystal intrinsic orientation effect on the piezoelectric response of multi-domain 0.26Pb(In1/2Nb1/2)O3–0.46Pb(Mg1/3Nb2/3)O3–0.28PbTiO3 (PIN-PMN-0.28PT) crystals was investigated by coordinate transformation method. The results indicate that crystal intrinsic orientation effect plays a crucial role in determining the piezoelectric properties of multi-domain crystals. Almost 58% and 69% of the transverse piezoelectric coefficients d31 and d32, respectively, and 67% longitudinal piezoelectric coefficient d33 of multi-domain PIN-PMN-0.28PT crystals poled along [011]c originate from crystal intrinsic orientation effect. For [001]c poled multi-domain PIN-PMN-0.28PT crystals, intrinsic orientation effect contributes to the transverse and longitudinal piezoelectric coefficient at least 79% and 74%, respectively.

Synthesis of KCa2Nb3O10 Crystals with Varying Grain Sizes and Their Nanosheet Monolayer Films As Seed Layers for PiezoMEMS Applications

The layered perovskite-type niobate KCa2Nb3O10 and its derivatives show advantages in several fields, such as templated film growth and (photo)catalysis. Conventional synthesis routes generally yield crystal size smaller than 2 μm. We report a flux synthesis method to obtain KCa2Nb3O10 crystals with significantly larger sizes. By using different flux materials (K2SO4 and K2MoO4), crystals with average sizes of 8 and 20 μm, respectively, were obtained. The KCa2Nb3O10 crystals from K2SO4 and K2MoO4 assisted synthesis were protonated and exfoliated into monolayer nanosheets, and the optimal exfoliation conditions were determined. Using pulsed laser deposition, highly (001)-oriented piezoelectric stacks (SrRuO3/PbZr0.52Ti0.48O3/SrRuO3, SRO/PZT/SRO) were deposited onto Langmuir-Blodgett films of Ca2Nb3O10(-) (CNO) nanosheets with varying lateral nanosheet sizes on Si substrates. The resulting PZT thin films showed high crystallinity irrespective of nanosheet size. The small sized nanosheets yielded a high longitudinal piezoelectric coefficient d33 of 100 pm/V, while the larger sized sheets had a d33 of 72 pm/V. An enhanced transverse piezoelectric coefficient d31 of -107 pm/V, an important input parameter for the actuation of active structures in microelectromechanical systems (MEMS) devices, was obtained for PZT films grown on CNO nanosheets with large lateral size, while the corresponding value on small sized sheets was -96 pm/V.

Constrained sintering and electrical properties of BNT–BKT lead-free piezoceramic thick films

Bi0.5(Na0.82K0.18)0.5TiO3 (BNKT) thick films were prepared by screen-printing on the alumina substrate. Grain growth behavior, constrained sintering processing, dielectric properties, ferroelectric properties and piezoelectric properties were studied. The results show that BNKT thick films exhibit a much lower grain growth rate and smaller grain size than bulk samples due to the constrained sintering on rigid substrates. The XRD measurement revealed that the residual tensile stress formed during sintering resulting from the constrained in-plane shrinking. The typical 80μm thick films demonstrate the relative dielectric constant of 775, dielectric loss of 3.6% at 1kHz, remnant polarization of 18.6μC/cm2, coercive field of 61kV/cm, and longitudinal effective piezoelectric coefficient, d33 of 105pm/V at room temperature. Compared with BNT-based piezoelectric bulk ceramics, the smaller longitudinal piezoelectric coefficient is related to the clamping effect of the substrate and the limited extrinsic piezoelectric contributions due to the reduced non-180° domain wall motions.

The negative piezoelectric effect of the ferroelectric polymer poly(vinylidene fluoride).

Piezoelectricity describes interconversion between electrical charge and mechanical strain. As expected for lattice ions displaced in an electric field, the proportionality constant is positive for all piezoelectric materials. The exceptions are poly(vinylidene fluoride) (PVDF) and its copolymers with trifluoroethylene (P(VDF-TrFE)), which exhibit a negative longitudinal piezoelectric coefficient. Reported explanations exclusively consider contraction with applied electric field of either the crystalline or the amorphous part of these semi-crystalline polymers. To distinguish between these conflicting interpretations, we have performed in situ dynamic X-ray diffraction measurements on P(VDF-TrFE) capacitors. We find that the piezoelectric effect is dominated by the change in lattice constant but, surprisingly, it cannot be accounted for by the polarization-biased electrostrictive contribution of the crystalline part alone. Our quantitative analysis shows that an additional contribution is operative, which we argue is due to an electromechanical coupling between the intermixed crystalline lamellae and amorphous regions. Our findings tie the counterintuitive negative piezoelectric response of PVDF and its copolymers to the dynamics of their composite microstructure.

Thickness-Dependent Monoclinic Phases and Piezoelectric Properties Observed in Polycrystalline (Pb0.94La0.04)(Zr0.60Ti0.40)O3 Thin Films

Ferroelectric thin films have received significant attention in view of their applications in microelectromechanical systems. Correlations between microstructure and polarization behavior have not been established. Polycrystalline (Pb0.94La0.04)(Zr0.60Ti0.40)O3 thin films with thicknesses ranging from 100 to 400 nm were prepared on the Pt(111)/Ti/SiO2/Si(100) substrates by a sol–gel method. Synchrotron X-ray diffraction results revealed that the films thinner than 150 nm possess an asymmetry-allowed monoclinic (MA) phase and undergo a MA–monoclinic MB–R phase sequence with increasing thickness. It was found that longitudinal piezoelectric coefficient d33 optimizes at 128 pm/V for 150 nm thick film. Above this thickness, a simple decreasing trend was observed. The presence of the monoclinic phase and (100) preferred orientation as well as crystalline quality are considered to play key roles in enhancing piezoelectric properties of the 150 nm thick film. Piezoelectric materials show a composition-related transition region where the crystal structure changes abruptly and the piezoelectric properties are maximal. In this study, an alternative approach is proposed in achieving excellent piezoelectric properties via a thickness-dependent constrain effect.

(100)-Textured KNN-based thick film with enhanced piezoelectric property for intravascular ultrasound imaging.

Using tape-casting technology, 35 μm free-standing (100)-textured Li doped KNN (KNLN) thick film was prepared by employing NaNbO3 (NN) as template. It exhibited similar piezoelectric behavior to lead containing materials: a longitudinal piezoelectric coefficient (d33) of ∼150 pm/V and an electromechanical coupling coefficient (kt ) of 0.44. Based on this thick film, a 52 MHz side-looking miniature transducer with a bandwidth of 61.5% at -6 dB was built for Intravascular ultrasound (IVUS) imaging. In comparison with 40 MHz PMN-PT single crystal transducer, the rabbit aorta image had better resolution and higher noise-to-signal ratio, indicating that lead-free (100)-textured KNLN thick film may be suitable for IVUS (>50 MHz) imaging.

Enhancing the operational range of piezoelectric actuators by uniaxial compressive preloading

The influence of the uniaxial preload on the off-resonance actuation performance of piezoelectric ceramics was investigated for compressive preload values up to −80 MPa. The study was performed on soft-type lead zirconate titanate (PZT), being the most widely used piezoelectric material. The samples were analysed using the proportional loading method, which enables the simultaneous application of electrical and mechanical loads, thereby mimicking the real operation conditions over the full stress–strain range. An increase of the blocking stress and the longitudinal piezoelectric stress coefficient was observed for all the applied preload values. The optimum properties, a blocking stress of −56 MPa and a free strain of 0.23%, were obtained at a preload value of −40 MPa and electric field of 2 kV mm − 1. This represents an increase of 16% and 20%, respectively, as compared to the values obtained at the smallest preload. In addition, the maximum work output was increased by about 28%. Finally, the results obtained at the lowest preload of −4 MPa using the proportional loading method were compared to the operational ranges determined by other methods. The comparison revealed large discrepancies between the methods, originating from the different order of the application of electrical and mechanical fields and the inherent nonlinearity of ferroelectric materials. This discrepancy results in decreased actuator performance due to impedance mismatching, demonstrating the need for accurate determination of the actuator’s operational range.

Piezoelectricity in K1−xNaxNbO3: First-principles calculation**Project supported by the National Basic Research Program of China (Grant No. 2013CB632900).

The piezoelectric properties of K1−xNaxNbO3 are studied by using first-principles calculations within virtual crystal approximation. To understand the critical factors for the high piezoelectric response in K1−xNaxNbO3, the total energy, piezoelectric coefficient, elastic property, density of state, Born effective charge, and energy barrier on polarization rotation paths are systematically investigated. The morphotropic phase boundary in K1−xNaxNbO3 is predicted to occur at x = 0.521, which is in good agreement with the available experimental data. At the morphotropic phase boundary, the longitudinal piezoelectric coefficient d33 of orthorhombic K0.5Na0.5NbO3 reaches a maximum value. The rotated maximum of is found to be along the 50° direction away from the spontaneous polarization (close to the [001] direction). The moderate bulk and shear modulus are conducive to improving the piezoelectric response. By analyzing the energy barrier on polarization rotation paths, it is found that the polarization rotation of orthorhombic K0.5Na0.5NbO3 becomes easier compared with orthorhombic KNbO3, which proves that the high piezoelectric response is attributed to the flattening of the free energy at compositions close to the morphotropic phase boundary.

Dielectric and piezoelectric properties of porous PZT–PCN ceramics sintered at different temperatures

Porous lead zirconate titanate–lead cobalt niobate 0.8Pb(Zr1/2Ti1/2)O3–0.2Pb(Co1/3Nb2/3)O3 (PZT–PCN) piezoelectric ceramics were fabricated by introducing pore-forming agent polymethyl methacrylate (PMMA), and the effect of sintering behavior on their microstructure, dielectric, and piezoelectric properties were investigated. The optimum sintering procedure was designed according to the thermogravimetric analysis of pore former. Finally the electrical properties were measured.The porosity of PZT–PCN ceramics decreased and the grain size increased with an increase in the sintering temperature at a fixed PMMA addition.“An increase in density with sintering temperature from 1050 to 1250°C results into an increase in longitudinal piezoelectric coefficient (d33) and relative dielectric constant (εr). This ‘in turn’ enhanced the hydrostatic figure of merit (dhgh) of the ceramics material”.The hydrostatic figure of merit (dhgh) of 24% porous PZT–PCN ceramics was eleven times more than that of dense ceramic. This kind of porous ceramic could be a promising candidate for medical diagnostic devices.

Compositional Dependence of the Young’s Modulus and Piezoelectric Coefficient of (110)-Oriented Pulsed Laser Deposited PZT Thin Films

In this contribution, we report on the compositional dependence of the mechanical and piezoelectric properties of Pb(Zr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Ti <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> )O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (PZT) thin films fabricated by pulsed laser deposition (PLD). These films grow epitaxially on silicon with a (110) preferred orientation and have excellent piezoelectric properties, which make them outstanding candidates for application in microelectromechanical system devices. Vibrometric measurements on capacitors showed that the effective longitudinal piezoelectric coefficient (d <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">33,f</sub> ) of 100-nm thick PZT films has a maximum value of 72 pm/V for a composition of x = 0.52. The Young's modulus was determined by measuring the difference in the flexural resonance frequencies of cantilevers before and after the deposition of the PZT thin films. The compositional dependence of the Young's modulus shows an increase in value for the Zr-rich compositions, which is in agreement with the trend observed in their bulk ceramic counterparts. From the obtained dielectric constant and d <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">33,f</sub> , we show that the calculated coupling coefficients of the PLD-PZT thin films have higher values for most of the compositions than their ceramic counterparts.