Large Piezoelectric Anisotropy Research Articles

Large piezoelectric anisotropy and high hydrostatic piezoelectric activity due to an appreciable orientation effect and porosity in novel 2–2–0 composites

The polarization orientation effect and porosity effect on the piezoelectric properties and related parameters are studied in 2–2-type composites based on domain-engineered relaxor-ferroelectric [011]-poled single crystals. The parameters, which are of great interest, are an anisotropy of the piezoelectric coefficients [Formula: see text], an anisotropy of the energy-harvesting figures of merit [Formula: see text] and the hydrostatic piezoelectric coefficient [Formula: see text]. An orientation of the main crystallographic axes in each polydomain single-crystal layer is described by angles [Formula: see text] and [Formula: see text]. Diagrams built for the first time show the ([Formula: see text]) regions, where a large anisotropy of [Formula: see text] (or [Formula: see text]) is achieved, and where inequality [Formula: see text] 1000 pC/N holds. A large local max [Formula: see text] = 1930 pC/N is achieved in a 2–2–0 PZN–0.065PT-based composite at the longitudinal piezoelectric coefficient [Formula: see text] = 2290 pC/N and figure of merit [Formula: see text] = 1.02[Formula: see text]10[Formula: see text] Pa[Formula: see text]. The aforementioned large parameters are to be of value in piezoelectric sensing, energy harvesting and hydroacoustics.

Novel lead-free composites with two porosity levels: large piezoelectric anisotropy and high sensitivity

A novel lead-free 1–3-type composite based on a ferroelectric domain-engineered single crystal is put forward. In the porous polymer matrix of this composite, two different porous structures are observed, and the effect of these structures on the piezoelectric performance, electromechanical coupling and related anisotropy parameters of 1–3-type composites is first studied. New diagrams that link the volume fractions of the single-crystal component and the porous regions in the polymer medium are built to show validity of conditions for a large anisotropy of piezoelectric coefficients and electromechanical coupling factors , and . In the composites based on the complex alkali niobate alkali tantalate single crystal with small piezoelectric anisotropy (/|| = 2.1), the three anisotropy factors /|| ≥ 5, /|| ≥ 5 and /|| ≥ 5 hold simultaneously due to the presence of layers with heavily prolate and heavily oblate air pores in the porous polymer matrix. The two porosity levels influence the elastic anisotropy of the porous matrix, and this leads to an increase in the three anisotropy factors across wide volume-fraction ranges. Of independent interest is the high piezoelectric sensitivity of the composites for which the condition ≥1 V m N−1 holds at their piezoelectric coefficient ≈ (200–500) pC N−1 and electromechanical coupling factors ≈ ≈ 0.8–0.9. The studied parameters of the novel piezo-active 1–3-type composites are of value for various applications such as active elements of piezoelectric transducers, energy-harvesting devices and sensors.

Anisotropy Factors and Electromechanical Coupling in Lead-Free 1-3-Type Composites.

The effective electromechanical properties and anisotropy factors of novel lead-free 1-3-type composites are studied to demonstrate their large piezoelectric anisotropy and considerable level of electromechanical coupling. The composites studied contain two single-crystal (SC) components and a polymer component. The first piezoactive component is a domain-engineered [001]-poled SC based on ferroelectric alkali niobates-tantalates, and this component is in the form of a system of long rods that are parallel to the poling axis . The second SC component is a system of spheroidal piezoelectric Li2B4O7 inclusions aligned in a continuous and relatively large polymer matrix. The SC rods are surrounded by an SC/polymer matrix, and the connectivity of the composite is 1-0-3. It is shown that the conditions , which indicates a large degree of anisotropy of the piezoelectric coefficients, and and , which indicate a large anisotropy of the electromechanical coupling factors (ECFs), can be achieved simultaneously in specific ranges of the component volume fractions and inclusion aspect ratios. Moreover, in the same volume-fraction and aspect-ratio ranges, large ECFs ( -0.9) are also achieved. In this context, the important role of the elastic properties of the continuous anisotropic matrix is discussed. The properties and anisotropy factors of the lead-free 1-3-type composites are compared to the similar parameters of conventional lead-containing piezoelectric materials, and the advantages of the composite system studied are described.

Theoretical Study on the Piezoelectric Performance of Lead‐Free 1–3‐Type Composites

The paper is devoted to the analysis of high‐performance piezo‐composites based on lead‐free ferroelectric single crystals. The composite consists of parallelepiped‐shaped single‐crystal rods which are surrounded by a laminar polymer matrix, and the composite as a whole is described by 1–2–2 connectivity. Such a composite structure promotes high piezoelectric sensitivity and hydrostatic response. Of particular interest are piezoelectric coefficients and , squared figure of merit , electromechanical coupling factor at the thickness‐mode oscillation, and hydrostatic parameters and . The influence of the laminar matrix on the aforementioned parameters is studied in a wide volume‐fraction range. Examples of maxima and large anisotropy of some effective parameters are discussed for the 1–2–2 composites based on [Lix(K1−yNay)1−x](Nb1−zTaz)O3:Mn single crystals. The role of elastic properties of the laminar matrix in achieving large hydrostatic parameters and piezoelectric anisotropy of these composites is emphasised. Their effective parameters are compared to those of composites based on the lead‐containing relaxor‐ferroelectric single crystals and to specific parameters of poled textured ceramics. Advantages of the studied composites over the relaxor‐ferroelectric‐based composites and textured ceramics open up new possibilities to apply the 1–3‐type lead‐free composites as active elements of piezoelectric sensors, hydrophones, energy‐harvesting, and transducer devices.

High piezoelectric sensitivity and related parameters of a novel lead-free 1–0–3 composite

ABSTRACTA piezoelectric performance of a novel 1–0–3 composite based on lead-free single crystals with 4mm symmetry is first analysed. Ferroelectric domain-engineered alkali niobate-tantalate based single crystals provide large values of the piezoelectric coefficients g*3j and g*h, squared figures of merit d*33 g*33 and d*h g*h, and a 0–3 matrix promotes a large piezoelectric anisotropy in specific volume-fraction ranges. An aspect-ratio effect concerned with spheroidal inclusions of a piezoelectric Li2B4O7 single crystal in a polymer medium is studied to show the considerable influence of these inclusions on the effective parameters of the composite. Values of g*33∼ 103 mV·m / N, g*h∼ (102–103) mV·m / N, d*33 g*33∼ 10−10 Pa−1, and d*h g*h∼ (10−11–10−10) Pa−1, and the large anisotropy of the piezoelectric coefficients d*3j and electromechanical coupling factors k*3j are achieved in the 1–0–3 composite based on a [001]-poled [Lix(K1-yNay)1-x](Nb1-zTaz)O3:Mn single crystal and make this composite suitable for piezoelectric sensor, energy-harvesting and hydroacoustic applications.

Piezoelectric Performance and Hydrostatic Parameters of Novel 2–2-Type Composites

This paper provides a detailed study of the structure-piezoelectric property relationships and the hydrostatic response of 2-2-Type composites based on relaxor-ferroelectric 0.72 Pb (Mg1/3Nb2/3)O3-0.28PbTiO3 single crystal (SC) material. Type I layers in the composite system are represented by a single-domain [111]-poled SC. Changes in the orientation of the crystallographic axes in the Type I layer are undertaken to determine the maximum values of the hydrostatic piezoelectric coefficients dh∗ , gh∗ , and eh∗ , and squared figure of merit dh∗ gh∗ of the composite. The Type II layers are a 0-3 composite whereby inclusions of modified PbTiO3 ceramic are distributed in a polymer matrix. A new effect is described for the first time due to the impact of anisotropic elastic properties of the Type II layers on the hydrostatic piezoelectric response that is coupled with the polarization orientation effect in the Type I layers. Large hydrostatic parameters gh∗ ≈ 300 -400 mV · m/N, eh∗ ≈ 40 -45 C/ [Formula: see text], and dh∗ gh∗ ∼10-11 Pa -1 are achieved in the composite based on the 0.72 Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 SC. Examples of the large piezoelectric anisotropy ( |d33∗ /d3f∗ | ≥ 5 or | g33∗ /g3f∗ | ≥ 5 ) are discussed. The hydrostatic parameters of this novel compositesystem are compared to those of conventional 2-2 piezocomposites.

Understanding the peculiarities of the piezoelectric effect in macro-porous BaTiO3

This work demonstrates the potential of porous BaTiO3 for piezoelectric sensor and energy-harvesting applications by manufacture of materials, detailed characterisation and application of new models. Ferroelectric macro-porous BaTiO3 ceramics for piezoelectric applications are manufactured for a range of relative densities, α = 0.30–0.95, using the burned out polymer spheres method. The piezoelectric activity and relevant parameters for specific applications are interpreted by developing two models: a model of a 3–0 composite and a ‘composite in composite’ model. The appropriate ranges of relative density for the application of these models to accurately predict piezoelectric properties are examined. The two models are extended to take into account the effect of 90° domain-wall mobility within ceramic grains on the piezoelectric coefficients . It is shown that porous ferroelectrics provide a novel route to form materials with large piezoelectric anisotropy at 0.20 ≤ α ≤ 0.45 and achieve a high squared figure of merit . The modelling approach allows a detailed analysis of the relationships between the properties of the monolithic and porous materials for the design of porous structures with optimum properties.

Advanced composites based on relaxor-ferroelectric single crystals: from electromechanical coupling to energy-harvesting applications

Domain-engineered relaxor-ferroelectric single crystals with compositions near the morphotropic phase boundary are considered as a key component for modern high-performance piezo-active composites. The advantages of using the relaxor-ferroelectric single crystals of solid solutions of (1 − x)Pb(Mg1/3Nb2/3)O3 − xPbTiO3 and (1 − y)Pb(Zn1/3Nb2/3)O3 − yPbTiO3 in piezo-active composites of 2–2 and 1–3 configurations are discussed by taking into account the complex relationships between the outstanding properties of the components and the effective parameters of the composite structure as a whole. Examples of their high piezoelectric activity, strong electromechanical coupling, large piezoelectric anisotropy, and large hydrostatic parameters of the composites demonstrate how the relaxor-ferroelectric single-crystal component improves the effective parameters and promotes the formation of non-monotonic volume-fraction dependences of particular effective parameters that are of interest for a variety of piezotechnical applications, such as transducers, sensors, hydrophones, and energy-harvesting devices.

Anisotropy of electromechanical properties and hydrostatic response of advanced 2–2‐type composites

AbstractThe paper reports results on the high performance of novel piezo‐active composites based on relaxor‐ferroelectric single crystals (SCs) of xPb(In0.5Nb0.5)O3–yPb(Mg1/3Nb2/3)O3–(1 − x − y)PbTiO3. We present a comparative analysis of the electromechanical properties of 2–2‐type composites based on single‐domain SCs from symmetry classes 3m and mm2. The parallel connection of the layers, the presence of an auxetic polymer component and the appropriate orientation of the main crystallographic axes of the single‐crystal layers lead to the development of large piezoelectric anisotropy and considerable hydrostatic piezoelectric response in comparison to the single‐crystal component. Effective piezoelectric coefficients $d_{3j}^{*} $ and electromechanical coupling factors $k_{3j}^{*} $ of the composites obey the conditions $d_{33}^{*} $/|$d_{31}^{*} $| ≥ 10, $d_{33}^{*} $/|$d_{32}^{*} $| ≥ 10, $k_{33}^{*} $/|$k_{31}^{*} $| ≥ 10, and $k_{33}^{*} $/|$k_{32}^{*} $| ≥ 10 at $k_{33}^{*} $ ≈ 0.6. Hydrostatic piezoelectric coefficients $d_{{\rm h}}^{*} $ ≈ 470 pC/N and $g_{{\rm h}}^{*} $ ∼ (102–103) mV m/N are one to two orders‐of‐magnitude larger than those of the single‐crystal component, which make it attractive for various piezotechnical applications. The role of the elastic properties of the components is discussed in connection with the large hydrostatic parameters.

Anisotropy Factors and Hydrostatic Parameters of 1–3-Type Piezo-Active Composites with Auxetic Polymer Matrices

Results on electromechanical properties and their anisotropy in 1–3-type composites with auxetic polyethylene matrices (Poisson's ratios from –0.83 to –0.20) are reported. The role of elastic properties of the auxetic component in forming a large piezoelectric anisotropy and hydrostatic piezoelectric coefficients d* h ≈ (1000–1500) pC/N and g* h ≈ (500– 600) mV.m/N, figures of merit, and electromechanical coupling factors is studied. Condition d*33/d*31→±∞ is valid at the volume fraction of ceramic 0.22≤ m*≤ 0.33, and m* correlates with the ratio c11/|c12| of elastic moduli of polymer. The effect of the aspect ratio of the elliptic cross section of rods on the volume-fraction dependence of d*3j , the piezoelectric anisotropy, and hydrostatic response is analysed.

Piezoelectric properties of Ca-modified Pb 0.6Bi 0.4(Ti 0.75Zn 0.15Fe 0.10)O 3 ceramics

Perovskite-structured Pb 0.6Bi 0.4(Ti 0.75Zn 0.15Fe 0.1)O 3 ceramics was reported with high Curie temperature T C of 705 °C and tetragonality of c/ a = 1.10, promising for high temperature applications with large piezoelectric anisotropy. In this paper, it was experimentally demonstrated to ease poling processing and enhance piezoelectricity through substituting lead with calcium of Pb 0.6− x Ca x Bi 0.4(Ti 0.75Zn 0.15Fe 0.1)O 3. For the x = 0.18 sample, electromechanical coupling factor ratio of k t / k p → ∞, dielectric constant of 380, piezoelectric coefficient d 33 of 80 pC/N, mechanical quality factor Q m of 50 and Curie point T C of 237 °C were obtained, which exhibits better piezoelectric performance than the (Pb 0.76Ca 0.24)(Ti 0.96(Co 0.5W 0.5) 0.04)O 3. The enhanced piezoelectric response was analyzed with relation to the reduction of tetragonality and Curie temperature.

XRD Study on D-Values of Modified PbTiO<sub>3</sub> Ceramics during Poling Process

The Calcium modified PbTiO3 ceramics with large piezoelectric anisotropy was poled in consecutive steps. X-ray diffraction (XRD) found that the values of inter-planar spacing, d002 and d200, increased with poling field at initial poling stages. A noticeable drop of the d¬002 and d200 at the coercive field was observed. The residual stresses measured by the  angle tilt method were introduced. The relations of d002-sin2ψ and d¬¬200-sin2ψ at different poling stages were simulated by a mathematic model. The linear terms in the model are related to the macro-stress which may cause an elastic deformation; the exponential term in the model is related to the micro-stress which may cause a plastic deformation by the 90o domain switch. The results show that macro-stress and micro-stress decreased and the decay speed along  angle increased as to the d002 lattice spacing. The residual stresses related to the d200 lattice spacing were almost not changed.

Seed effect in fabrication of calcium modified lead titanate ceramics

The calcium modified lead titanate [Pb 0.76Ca 0.24Ti 0.96W 0.02Co 0.02O 3 + MnO 0.4 wt.% + NiO 0.3 wt.% (PCaT)] bulk ceramics were fabricated. It was found that the ceramics with pure perovskite phase could be fabricated from a sol–gel powder that was annealed before being doped. The c/ a ratios of the unit cell of un-doped PCaT powder and doped PCaT ceramics were 1.056 and 1.042, which were calculated according the X-ray diffraction patterns. The maximum value of piezoelectric constant d 33, thickness electromechanical coupling coefficient k t, electromechanical quality factor Q and dielectric permittivity ɛ of the ceramics are 67 pC N −1, 0.52, 470 (at thickness resonance mode) and 200, respectively. The effect of powder fabrication procedure on crystalline phase purity and the function of doping element were discussed. The cause of large piezoelectric anisotropy was also investigated.

Piezoelectric properties of PbTiO3-based 0–3 and 0–1–3 composites

The effective piezoelectric coefficients of novel 0–3 ‘relaxor-ferroelectric Pb(A1/3B2/3)O3–PbTiO3-type single-crystal–ferroelectric PbTiO3-based ceramic’ and 0–1–3 ‘relaxor-ferroelectric Pb(A1/3B2/3)O3–PbTiO3-type single-crystal–ferroelectric PbTiO3-based ceramic–polymer’ composites are determined at various volume concentrations of piezo-active components. The role of the piezo-active single-crystalline and ceramic components in the non-monotonic concentration dependence of the piezoelectric properties of these composites is analysed. First, some empirical relationships among electromechanical constants of the components are given and discussed, which guarantee considerably high values of the hydrostatic piezoelectric coefficients and of the above-mentioned 0–3 composites with spheroidal inclusions. Next, it is shown that the presence of the relaxor-ferroelectric component in the 0–1–3 composite results in an unusual concentration behaviour of its piezoelectric coefficients and , which has not been described before in papers on the well-studied 1–3 ‘ferroelectric ceramic – polymer’ composite. Examples of the large piezoelectric anisotropy of the 0–1–3 composite (i.e. conditions , , and , where are electromechanical coupling factors) are also considered and discussed.

Electron spin resonance study of the conversion of Mn 4+ to Mn 2+ in the Pb 1− xEu xTi 1− yMn yO 3 ceramic system

Electron spin resonance (ESR) studies of the Pb 0.88Eu 0.08 Ti 1− y Mn y O 3 ( y=0.0, 0.1, 0.2, 0.3); PbTi 0.98Mn 0.02O 3 and PbTiO 3 ferroelectric ceramics are reported. The conversion of Mn 4+ to Mn 2+ in the Pb 0.88Eu 0.08Ti 1− y Mn y O 3 ceramics compositions have been clearly demonstrated. The presence of the Eu cation is necessary for such conversion to take place and it does not take place in the PbTi 0.98Mn 0.02O 3 ceramic. Analysis of its ESR spectra indicates that Mn 4+ substitution occurs at the Ti 4+ at two different ESR-distinguishable locations. Both factors, namely the Mn 4+→Mn 2+ conversion and the Eu 3+ presence are responsible for the large microstrain and the deterioration of crystallinity observed in this ceramics, which seemed to play a crucial role for reading large piezoelectric anisotropy in the system.

Study of low—temperature sintering modified PbTiO3 piezoelectric ceramic

A new low-temperature sintering modified PbTiO3 piezoelectric ceramic material was prepared by adding Bi(Cd1/2Ti1/2)O3, MnO2, SiO2. The modified PT material has excellent properties such as low-sintering temperature, high piezoelectric activities, large piezoelectric anisotropy, high mechanical quality factor, low dielectric constant and dielectric loss. The main parameters are Kt=0.49, Kp=0.027, Kt/Kp=18.2, d33=65 × 10−12C-N−1, Qm=514, ρv = 7.4 × 103kg−m−3, Tc=312°C, ε T 33/ε0 = 177, tanδ=0.63%. It shows great application prospects in the fields of multilayer piezoelectric filter and multilayer piezoelectric step-down transformer.

A Large Piezoelectric Anisotropy of a Three-Component Composite with Variable Connectivity

Proposed are two types of three-component piezoelectric composites that change connectivity from 2-2 to 1-3 and contain polarized ferroelectric ceramic and polymer components, i.e., “layer 1 reinforced by rods–layer 2–layer 1 reinforced by rods– . . . ” (type 1) and “laminated rods (layer 1–layer 2–layer 1– . . . ) embedded in a matrix” (type 2). Some cases of the large anisotropy of piezoelectric coefficients d 33 * /∣d 31 * ∣ and e 33 * /∣e 31 * ∣ are analyzed for the composites of the type 1. Original cases of simultaneous reaching d 33 * /∣d 31 * ∣ → 0 and e 33 * /∣e 31 * ∣ > 10 as well as e 33 * /∣e 31 * ∣ → ∞ and d 33 * /∣d 31 * ∣ → ∞ at different volume concentrations of the components in the composites of the type 2 are also considered. It is shown that these ratios essentially depend on electromechanical constants of the components, their volume concentrations, microgeometry, as well as on jumps of these constants and internal fields at boundaries between the components.

Tailoring material properties by structure design–radially poled piezoelectric cylindrical tube

Abstract In many applications such as hydrophone and ultrasonic transducers, materials with large piezoelectric anisotropy are preferred in order to suppress the interfering signals from lateral modes. It has been shown that piezoelectric anisotropy can be significantly improved by structure design. For instance, for a radially poled cylindrical tube, the effective transverse piezoelectric response can be tuned to zero. In this work, the effective piezoelectric responses of lead zirconate titanate (PZT) and lead magnesium niobate-lead titanate (PMN-PT) ceramic cylindrical tubes were studied. Large piezoelectric anisotropy with a high effective uniaxiai coefficient has been obtained for both materials. It has been shown that near zero effective d 31 can be achieved for a PZT tube with a proper dimension ratio of ro/Ro , where ro , andRo are inner and outer radii of the tube, respectively. While for a PMN-PT tube, the effective piezoelectric responses can be tuned by the ratio of ro/RO as well as the bias f...

The effect of domain structure on electromechanical properties of PbTiO3,-based ferroelectrics

Abstract Dependences of the tensor components of the piezoelectric moduli, dielectric permittivities and elastic compliances on the volume concentration of 90° domains in the grains and on the temperature have been analyzed for ceramic PbTiO3. Possibilities for realization of the large piezoelectric anisotropy and its temperature variation in the crystals and ceramics of PbTiO3 have been discussed.

Piezoelectricity in the Field‐Induced Ferroelectric Phase of Lead Zirconate‐Based Antiferroelectrics

The piezoelectric characteristics were investigated in the field‐induced ferroelectric phase of the antiferroelectric Pb0.99 Nb0.02[(Zr0.6Sn0.4) 1 −yTiy]0.98O3 family. The electromechanical coupling factors kp and kt were measured, and the piezoelectric anisotropy was calculated. The piezoelectricity was controlled easily by the applied electric field pulse. The large piezoelectric anisotropy of these materials in comparison to that of conventional PZT piezoelectric materials makes them very applicable for ultrasonic probes and surface acoustic wave filters.