Search

The morphotropic phase boundary (MPB) Ba 0.85 Ca 0.15 Zr 0.10 Ti 0.90 O 3 composition is successfully transferred into <001>-textured ceramic having Lotgering factor f-74 % (abbreviated as BCZT-T74) using high aspect ratio BaTiO 3 -template particles via templated grain growth (TGG) method. The microstructural aspects reveal the distinctive grain growth formation for non-textured (BCZT-NT) and textured (BCZT-T74) ceramics; confirming the proper grain growth formation for textured ceramics. The polarization behavior was tested at 1 Hz, 5 Hz, and 10 Hz electric field frequencies by applying a voltage bias of 1000 V; the BCZT-NT ceramics show more variation in remnant polarization (P r) as well as maximum polarization (P max) peak position while BCZT-T74 ceramics exhibit nearly steady values. The frequency-dependent variation in P r (i.e. ΔP r) for non-textured and textured BCZT ceramics is ±11.08 % and ±3.25 % respectively in the frequency range 1Hz–10Hz at an applied voltage bias of 1000 V. The bipolar strain-electric field (S-E) butterfly loop evidences the typical piezoelectric nature; for both non-textured and textured BCZT ceramics having the effective piezoelectric strain coefficient d 33 * of 576 pm/V and 657 pm/V respectively. The BCZT-NT and BCZT-T74 ceramics revealed the average positive strain % values of 0.063 % and 0.1123 % and negative strain % values of 0.003985 % and 0.02281 % respectively at the applied voltage 1000 V functioning at 1Hz. The enhancement in negative strain% for BCZT-T74 ceramics is > 5.70 times higher than BCZT-NT ceramics. The variation in positive strain (i.e. ΔS + ve) and variation in negative strain (i.e. ΔS -ve) for non-textured ceramics is ±11.74 % and ±67.34 %, however, for textured ceramics is only ±3.33 % and ±5.00 % respectively. The BCZT-NT and BCZT-T74 ceramics exhibit the piezoelectric charge coefficient (d 33) of 370 pC/N and 520 pC/N (1.4 times that of BCZT-NT ceramics) respectively. The electrostrictive coefficient (Q 33) of BCZT-T74 ceramics is 0.039 m4/C2, which is > 2 times higher than BCZT-NT ceramics as well as commercially used toxic PZT-5H ceramics. Therefore, less variation in a strain, as well as polarization nature with varying frequencies and enhancement in piezo properties, suggests the present textured MPB BCZT-T74 ceramics is a promising candidate for piezoelectric devices functioning at the wide range of applied electric field frequencies. [ABSTRACT FROM AUTHOR]

Bone defects are a significant health problem worldwide. Novel treatment approaches in the tissue engineering field rely on the use of biomaterial scaffolds to stimulate and guide the regeneration of damaged tissue that cannot repair or regrow spontaneously. This work aimed at developing and characterizing new piezoelectric scaffolds to provide electric bio-signals naturally present in bone and vascular tissues. Mixing and extrusion were used to obtain nanocomposites made of polyhydroxybutyrate (PHB) as a matrix and barium titanate (BaTiO3) nanoparticles as a filler, at BaTiO3/PHB compositions of 5/95, 10/90, 15/85 and 20/80 (w/w%). The morphological, thermal, mechanical and piezoelectric properties of the nanocomposites were studied. Scanning electron microscopy analysis showed good nanoparticle dispersion within the polymer matrix. Considerable increases in the Young's modulus, compressive strength and the piezoelectric coefficient d31 were observed with increasing BaTiO3 content, with d31 = 37 pm/V in 20/80 (w/w%) BaTiO3/PHB. 3D printing was used to produce porous cubic-shaped scaffolds using a 90° lay-down pattern, with pore size ranging in 0.60–0.77 mm and good mechanical stability. Biodegradation tests conducted for 8 weeks in saline solution at 37 °C showed low mass loss (∼4%) for 3D printed scaffolds. The results obtained in terms of piezoelectric, mechanical and chemical properties of the nanocomposite provide a new promising strategy for vascularized bone tissue engineering. [ABSTRACT FROM AUTHOR]

The structural and physical properties of hydroxyapatite with the substitutions of Sr/Ca were studied by density functional theory calculations using Quantum ESPRESSO. The calculation of the lattice constants upon substitution of Sr/Ca in HAP was compared with the experimental data and showed similar increase in these parameters after the Sr/Ca substitutions. The changes in the band gap ΔEg and the electron work function Δϕ after Sr/Ca substitutions were estimated. The changes in the polarization and piezoelectric properties upon Sr/Ca substitution were calculated using the new quantum-chemical semi-empirical PM7, PM6-D3H4 (MOPAC) calculations. [ABSTRACT FROM AUTHOR]

To determine all the material constants of a piezoelectric crystal using the IEEE resonance method or ultrasonic method, several samples with specific geometries and orientations are required, and the obtained results may be somewhat self-contradictory. The resonant ultrasound spectroscopy (RUS) can determine full material constants of a single piezoelectric sample by matching the numerically computed eigenfrequencies to the measured resonance spectrum. However, typically the usage of PZT transducers for excitation and reception makes the testing complicated and may add additional mass and damping. In this work, we propose a new method called partial electrode electromechanical impedance spectroscopy (PE-EMIS), which can obtain all the elastic, piezoelectric constants, and related internal frictions of a piezoelectric crystal by just using a single sample without additional transducers. In PE-EMIS, two small PEs are fabricated on one corner of a piezoelectric sample, and the sample’s resonance frequencies, along with the internal frictions of the ${k}$ th eigenmode, can be accurately obtained from the conductance spectrum measured using an impedance analyzer. The PE-EMIS experiment is carried out on a rectangular parallelepiped PZT-4 piezoelectric ceramic, and the extracted material constants are highly repeatable. Three of the extracted elastic constants (${c}_{{11}}^{E}$ , ${c}_{{33}}^{D}$ , and ${c}_{{66}}^{E}$) are validated by the traditional wave propagation method. Due to its simplicity, convenience, and accuracy, the proposed PE-EMIS is expected to be widely used for characterization of piezoelectric materials in near future. [ABSTRACT FROM AUTHOR]

• The stability of newly discovered two-dimensional Janus XY (X/Y=P, As, Sb, Bi, and X≠Y) are confirmed. • Janus XY exhibit high out-of-plane piezoelectric coefficients, paired with remarkable electronic carrier mobilities. • Janus XY stand out in water splitting due to their favorable band edges and electrostatic potential gradients. • Applying biaxial strain can effectively enhance the photocatalytic water splitting properties of these materials. Janus materials, with unique physical and chemical properties, show promise in turning solar energy into clean hydrogen through photocatalytic water splitting. Herein, utilizing first-principles calculations, we have confirmed the stabilities of newly discovered two-dimensional XY materials (X/Y=P, As, Sb, Bi, X≠Y), unveiling their promising capabilities in photocatalytic water splitting. These Janus structures exhibit broad bandgaps, paired with remarkable electron carrier mobilities. Their out-of-plane piezoelectric coefficients (d 31) varying from 0.10 pm/V to 0.31 pm/V, surpass those of many typical two-dimensional materials, highlighting their considerable potential in energy conversion applications. These materials stand out in water splitting due to their favorable band edges and electrostatic potential gradients, achieving solar-to-hydrogen (STH) efficiencies above 20 % and visible light absorption efficiencies over 10 %. Remarkably, Janus PBi showcases STH and visible light absorption efficiencies up to 29.01 % and 19.33 %, respectively. By using biaxial strain, Janus PAs and PSb can reach a peak STH efficiency of over 30 % and a top visible light absorption efficiency above 20 %. Janus AsSb (PBi) exhibits exceptionally high photocatalytic activity for the oxygen (hydrogen) evolution reaction. These attributes suggest that these Janus XY materials are promising contenders as photocatalytic catalysts for water-splitting applications. [ABSTRACT FROM AUTHOR]

Distinct from conventional 2H‐MoS2, recently synthesized 3R‐MoS2 exhibits a noncentrosymmetric atomic structure of the trigonal "building blocks" and, thus, remarkable piezoelectric characteristics of ultrathin 3R‐MoS2 flakes are predicated theoretically. This paper reveals, for the first time, very high piezoelectricity in 3R‐MoS2 flakes experimentally. Through applying mechanical stress to a 48 nm 3R‐MoS2 flake, a high output power density of 65 mW m‐2 is obtained and is at least one order larger than those from the corresponding monolayer MoS2 flake. With out‐of‐plane lateral piezoresponse force microscopy technique, the two piezoelectric coefficients d33 and d13 are analyzed to be ≈0.9 and ≈1.6 pm V‐1, respectively. These piezoelectric coefficients are not apparently dependent on the flake thickness. The findings suggest that 3R‐MoS2 is of excellent piezoelectric properties and it can be an excellent material for novel piezoelectric devices. [ABSTRACT FROM AUTHOR]

The structural and physical properties of hydroxyapatite (HAP) with the substitution of Sr/Ca and Mg/Ca are studied. The changes in the HAP properties are studied by various methods of density functional theory calculations. The calculation of the lattice constants upon substitution of Sr/Ca in HAP compared with the experimental data shows similar increase in these parameters after substitution of Sr/Ca. The values of bulk modulus, band gap Eg, and the work function Δϕ before and after both substitutions of Sr/Ca and Mg/Ca are calculated. The changes in piezoelectric properties upon Mg/Ca substitution are obtained. [ABSTRACT FROM AUTHOR]

In this paper, two methods (magnetic stirring and mechanical ball milling) were used to modify the surface of lead zirconate titanate (PZT) particles. Then, poly(vinylidene fluoride) (PVDF)/PZT piezoelectric films were prepared by extrusion casting and solvent casting. We investigated the mechanical, dielectric, ferroelectric, and piezoelectric properties, as well as the breakdown strength of the PVDF/PZT films. We found that adding PZT particles improved the mechanical stability of the films under variable temperature conditions. Modification by the UP-105 titanate coupling reagent further improved the combination and dispersion of PZT@105 particles in PVDF. The films prepared by extrusion casting showed improved properties in terms of density, dielectric constant, breakdown strength, and piezoelectric coefficient. The piezoelectric coefficient (d33) of the PVDF/PZT@105 composite film (with 25 wt.% PZT@105) prepared by extrusion casting reached 35 pC/N, and the electromechanical strain ratio was almost 1.6%, which is higher than that of piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

This paper presents the results of ultrasonic measurements in trigonal LiTaO3 crystals. The samples of direct section with faces perpendicular to the main crystallographic axes and X/45 sections of LiTaO3 crystals were manufactured for experimental studies. The velocities of longitudinal and transverse acoustic waves along the three principal crystallographic axes and two additional axes in theYZ plane in trigonal crystals of point group 3m LiTaO3 crystals were measured using the pulse-echo overlap method. In the piezoelectric crystals, elastic and electrical properties are related and the propagation of an acoustic wave is accompanied by the appearance of electric fields, which must be taken into account in the calculations. The relations for the complete determination of all components of the matrices of elastic stiffness and piezoelectric coefficients based on all necessary acoustic wave velocities measured were derived from the Christoffel equation for the piezoelectric crystals. Using the obtained ratios, all components of the tensors of piezoelectric coefficients, elastic stiffness constants, as well as all elastic compliances of LiTaO3 crystals are calculated. The obtained results are consistent with the literature data and will be used in further measurements and calculation of the spatial anisotropy of induced (electro-, piezo- and acousto-optical) effects on the same crystal samples in order to select the most effective geometry of their possible practical use. [ABSTRACT FROM AUTHOR]

We propose a two-sublattice proton ordering model for the quasi-one-dimensional CsH2PO4 ferroelectric with hydrogen bonds, which takes into account contributions to the energy of the proton subsystem that are linear in the lattice strains ε1, ε2, ε3, and ε5. The model also takes into account the dependence of the effective dipole moments of pseudospins on the order parameters, which enables us to coordinate the values of the effective dipole moments in the paraelectric and ferroelectric phases. Within this model in the two-particle cluster approximation for the short-range interactions and in the mean field approximation for the long-range interactions, the behavior of spontaneous polarization, longitudinal dielectric permittivity, piezoelectric and elastic characteristics, and molar heat capacity under the influence of uniaxial and hydrostatic pressure and a longitudinal electric field are investigated. [ABSTRACT FROM AUTHOR]

We propose a two-sublattice proton ordering model for the quasi-one-dimensional CsH2PO4 ferroelectric with hydrogen bonds, which takes into account contributions to the energy of the proton subsystem that are linear in the lattice strains ε1, ε2, ε3, and ε5. The model also takes into account the dependence of the effective dipole moments of pseudospins on the order parameters, which enables us to coordinate the values of the effective dipole moments in the paraelectric and ferroelectric phases. Within this model in the two-particle cluster approximation for the short-range interactions and in the mean field approximation for the long-range interactions, the behavior of spontaneous polarization, longitudinal dielectric permittivity, piezoelectric and elastic characteristics, and molar heat capacity under the influence of uniaxial and hydrostatic pressure and a longitudinal electric field are investigated. [ABSTRACT FROM AUTHOR]

In this paper, we deal with a theoretical and predictive study of the influence of the applied pressures on the structural, elastic and piezoelectric properties of the rhombohedral BiAlO3 perovskite (R3c space group) phase by combining both the density functional theory (DFT) and the density functional perturbation theory (DFPT) included in the ABINIT code. The results indicate a decrease in structural cell volume and the elastic constants appear to be more intense as the applied pressure increases. Due to the increase in the direct piezoelectric coefficient (e33) and the decrease of the elastic constant (c33), the converse piezoelectric coefficients (d33) tend to improve with increased pressure applied. At a pressure of 10 GPa, the value of the direct piezoelectric constant reached 6.23 C/m2 which becomes an indirect competitor to lead zirconate titanate (PZT). The dielectric constants and born effective charge at high pressure have been calculated. Our results agree well with the available experimental and theoretical results. Our findings, especially piezoelectricity, can help in various applications of high‐pressure devices such ultrasonic transducer. [ABSTRACT FROM AUTHOR]

A comparative study on a set of electrophysical parameters of novel piezo-active composites is carried out. These composites are based on ferroelectric ZTS-36 ceramic of the PZT type. The second (piezo-passive) component is either clay or corundum ceramic, and its volume fraction mc is varied from 0.01 to 0.10 (clay) or from 0.01 to 0.12 (corundum). The studied composites are characterised by elements of 3–0 connectivity patterns that include not only the aforementioned components but also air pores. Experimental volume-fraction (mc) dependences of the piezoelectric coefficients d 3 j * and g 3 j * (j = 1 and 3), their anisotropy ζd* = d 33 * / d 31 * , mechanical quality factor Q M * , and planar electromechanical coupling factor k p * are compared for the clay- and corundum-containing composites. The corundum-containing composite exhibits large Q M * values (up to 858) at |ζd*| < 3.2, and the clay-containing composite is characterised by relatively large g 33 * values (about 50–60 mV m/N) at |ζd*| < 4.9. The experimental volume-fraction dependences of d 3 j * , g 3 j * , ζd*, and k p * are interpreted within the framework of a model of a 3–0-type composite with spheroidal inclusions (piezo-passive component and pores). Agreement between our modelling results and experimental values of the electrophysical parameters is observed in the studied mc range. [ABSTRACT FROM AUTHOR]

Using density functional theory calculations, atomic and electronic structure of defects in monolayer GeS were investigated by focusing on the effects of vacancies and substitutional atoms. We chose group IV or chalcogen elements as substitutional ones, which substitute for Ge or S in GeS. It was found that the bandgap of GeS with substitutional atoms is close to that of pristine GeS, while the bandgap of GeS with Ge or S vacancies was smaller than that of pristine GeS. In terms of formation energy, monolayer GeS with Ge vacancies is more stable than that with S vacancies, and notably GeS with Ge substituted with Sn is most favorable within the range of chemical potential considered. Defects affect the piezoelectric properties depending on vacancies or substitutional atoms. Especially, GeS with substitutional atoms has almost the same piezoelectric stress coefficients eij as pristine GeS while having lower piezoelectric strain coefficients dij but still much higher than other 2D materials. It is therefore concluded that Sn can effectively heal Ge vacancy in GeS, keeping high piezoelectric strain coefficients.

Effects of La3+ admixture in barium lanthanum titanate (BLT) ceramics system with colossal permittivity on performance of prospective piezoelectric cold plasma application were studied. Usage of cold atmospheric pressure plasma appears promising in terms of industrial and healthcare applications. Performed investigation provide consistent evaluation of doping lanthanum amount on piezoelectric coefficients values with simultaneous capability of charge accumulation for effective plasma generation. Modification of ferroelectric materials with heterovalent ions, however with the lower radii than the original atoms, significantly affects their domain mobility and consequently electromechanical properties. To determine the piezoelectric coefficients, the resonance-antiresonance method was implemented, and values of piezoelectric and dielectric parameters were recorded. Finally the results indicated that addition of 0.4 mol.% of La3+ ions to the ceramic structure maximally increased the values of piezoelectric coefficient to d33 = 20 pC/N and to huge dielectric constant to ε33T = 29277.

The effects appearing under the simultaneously applied mechanical stress and electric field are studied. We use a model of glycinium phosphite ferroelectric, modified by taking into account of piezoelectric coupling of the ordering structure elements with the lattice strains. Within the framework of two-particle cluster approximation, the components of polarization vector and the static dielectric permittivity tensor as well as piezoelectric and thermal characteristics are calculated. The separate and simultaneous effects of shear stress and electric field on the ferroelectric phase transition in the crystal are studied and mutually compared. [ABSTRACT FROM AUTHOR]

In this study, a multi-parameter perturbation method is used for the solution of a functionally-graded, thin, circular piezoelectric plate. First, by assuming that elastic, piezoelectric, and dielectric coefficients of the functionally-graded materials vary in the form of the same exponential function, the basic equation expressed in terms of two stress functions and one electrical potential function are established in cylindrical coordinate system. Three piezoelectric coefficients are selected as perturbation parameters, and the established equations are solved by the multi-parameter perturbation method, thus obtaining up to first-order perturbation solutions. The validity of the perturbation solution obtained is verified by numerical simulations, based on layer-wise theory. The perturbation process indicates that adopting three piezoelectric coefficients as perturbation parameters follows the basic idea of perturbation theory—i.e., if the piezoelectricity may be regarded as a kind of introduced disturbance, the zero-order solution of the disturbance system corresponds exactly to the solution of functionally-graded plates without piezoelectricity. The result also indicates that the deformation magnitude of piezoelectric plates is smaller than that of plates without piezoelectricity, due to the well-known piezoelectric stiffening effect.

The results are based on the first principle modeling and calculations of hydroxyapatite (HAP) nanostructures, especially in ordered hexagonal phase. HAP structures were studied using Local Density Approximation (LDA) method with calculations of Density of States (DOS) and molecular modeling by HyperChem. Computed data show that monoclinic and hexagonal phases can coexist, especially in the ordered states. Calculated piezoelectric coefficient for hexagonal phase d33 ∼6.4 pm/V is consistent with previously obtained value for monoclinic HAP (15.7 pm/V) and experimental data. The estimated pyroelectric coefficient at the order of γ ∼ 10–100 μC/(m2K) is also in line with experimental data. [ABSTRACT FROM AUTHOR]

Highlights • A unique in-situ Berlincourt-type high temperature d 33 meter was designed. • The depolarization is directly related to the structural phase transition. • Compared with ex-situ technology, in-situ test data are more accurate. Abstract Thermal depolarization is an insurmountable obstacle to the application of piezoceramics and there is still controversy about its physical origin. In this work, taking four representative piezoceramics (0.94(Na 0.5 Bi 0.5)TiO 3 -0.06BaTiO 3 , 0.2Pb(Zn 1/3 Nb 2/3)O 3 -0.8Pb(Zr 0.5 Ti 0.5)O 3 , 0.36BiScO 3 -0.64PbTiO 3 and Ba 0.85 Ca 0.15 Ti 0.9 Zr 0.1 O 3) as an example, by using a designed in-situ Berlincourt-type high-temperature d 33 meter, combined with variable temperature X-ray diffraction and dielectric temperature spectrum test, it was confirmed the depolarization behavior is directly related to the structural phase transition, meanwhile it is reasonable to apply the peak value of piezoelectric coefficient with temperature, T dp , as the depolarization characteristic temperature. More importantly, the original in-situ varied temperature d 33 meter design helps to investigate the temperature dependent piezoelectric mechanism of various piezoceramics. [ABSTRACT FROM AUTHOR]

Abstract We report on the correlation between structural, ferroelectric, piezoelectric and dielectric properties of the (1-x) Ba 0.7 Ca 0.3 TiO 3 - x BaTi 0.8 Zr 0.2 O 3 (x = 0.45, 0.55; abbreviated as 55BCT30 and 45BCT30) ceramics close to morphotropic phase boundary (MPB) region. The 55BCT30 and 45BCT30 ceramics were synthesized by the standard, high-temperature solid state ceramic method. X-ray diffraction (XRD) along with Rietveld refinement indicate that the 55BCT30 ceramics exhibit rhombohedral (R , space group R 3 m), orthorhombic (O, space group Amm 2) and tetragonal (T, space group P 4 mm) phases while 45BCT30 ceramics exhibit only T and O phases. The temperature dependent Raman spectroscopy measurements confirm the structure and phase transformations observed from XRD. All the ceramics are chemically homogeneous and exhibit a dense microstructure with a grain size of 5–7 µm. The presence of polarization-electric field and strain-electric field hysteresis loops confirm the ferroelectric and piezoelectric nature of the ceramics. The polarization current density-electric field curves show the presence of two sharp peaks in opposite directions indicating the presence of two stable states with opposite polarity. Higher values of direct piezoelectric coefficient (d 33 ~ 360 pC/N) were observed due to the existence of low energy barrier near MPB region and polymorphism. The 55BCT30 ceramics exhibit a higher value of electrostrictive coefficient (Q 33 ~ 0.1339 m4/C2) compared to the well-known lead-based materials. The temperature dependent dielectric measurements indicate the O to T phase transition for 55BCT30 and 45BCT30. These ceramics exhibit a Curie temperature (T c) of 380 K with a dielectric maximum of ~ 4500. [ABSTRACT FROM AUTHOR]

The polycrystalline samples of gadolinium-modified lead-zirconate-titanate (Pb1−xGdx (Zr0.52Ti0.48)1−x/4O3) (x = 0, 0.07, 0.10 and 0.12) (PGZT x/52/48) ceramics near morphotropic-phase boundary were prepared using conventional solid-state reaction route. XRD patterns show the formation of single-phase compounds in rhombohedral crystal system. SEM textures of the samples reveal uniform grain distribution. Frequency and temperature dependence of dielectric constant of the materials indicates non-relaxor behavior and indication of the diffuse phase transition at higher values of Gd concentration. The temperature dependence of P-E loops confirms ferroelectricity in the materials. The piezoelectric studies of the samples show enhancement in piezoelectric coefficients on substitution of Gd at the Pb site. [ABSTRACT FROM AUTHOR]

Abstract: The high and low field ferroelectric response of freestanding PbZr0.52Ti0.48O3 (PZT) films, with texture varying from 100% (001) to 100% (111) was investigated via 500 nm thick PZT unimorphs deposited on the same substrate. It is shown that the ferroelectric and piezoelectric properties depend strongly on texture, and the effective transverse strain and stress coefficients vary linearly with %(001) and %(111) texture factors. PZT films with 100% (001) orientation displayed 150%, 140%, and 80% larger linear piezoelectric strain coefficient, saturated strain coefficient, and saturated stress coefficient, respectively, compared to films with 100% (111) orientation. As a result, pure (001) textured PZT films with 20% higher dielectric constant have 50% higher figure of merit in sensing than films with pure (111) texture. The piezoelectric and ferroelectric properties of all but one combinations of (001) and (111) texture were shown for the first time to be bounded by the values for 100% (001) and 100% (111) texture. A notable exception was PZT films comprised of 73% (001) and 27% (111) texture which showed stable piezoelectric coefficients at all electric fields, with major technological implication to low power microdevices. Finally, the coercive field was shown to decrease with (001) texture factor and excess‐Pb in the PZT and the PbTiO3 seed layer. [ABSTRACT FROM AUTHOR]

The piezoelectric devices made of ZnO nanowires have received a great interest in the past decade as potential nanogenerators and sensors. However, their characteristics are still limited significantly by the screening of the piezoelectric potential generated under mechanical solicitations, originating from the high density of free electrons in ZnO nanowires. In order to tackle that issue, we develop the compensatory Sb doping of ZnO nanowires grown by chemical bath deposition, both in the low- and high-pH regions using Sb glycolate and ammonia as chemical additives. The adsorption process of Sb(III) species on the positively charged surfaces of ZnO nanowires proceeds through attractive electrostatic forces, resulting in the significant incorporation of Sb dopants with an atomic ratio in the range of 0.11–0.45%. The optical properties of Sb-doped ZnO nanowires exhibit additional phonon modes related to Sb dopants in the range of 500–750 cm-1 in the Raman spectra, and some specific characteristics in the nature and intensity of radiative recombination in the cathodoluminescence spectra. Importantly, the integration of Sb-doped ZnO nanowires encapsulated in PMMA and grown on PDMS into flexible piezoelectric dynamic strain sensors is shown to drastically boost the piezoelectric charge and voltage coefficients by a factor of 2.65 and 1.91, following the significant incorporation of Sb dopants. A subsequent thermal annealing under oxygen atmosphere is revealed to further increase the piezoelectric charge and voltage coefficients by an additional factor of 1.38 and 1.49, following the activation of Sb doping and engineering of hydrogen-related defects. Two figures-of-merit are eventually derived from the piezoelectric charge and voltage coefficients and their values for flexible piezoelectric composites made of annealed Sb-doped ZnO nanowires are compared to more conventional piezoelectric materials, showing their high potential for medical devices. The present findings highlight the strategy consisting in simultaneously introducing compensatory acceptors and engineering hydrogen-related defects to reduce the screening effect, representing an additional powerful way to enhance the characteristics of the piezoelectric devices integrating ZnO nanowires. [Display omitted] • The growth of Sb-doped ZnO nanowires is developed using chemical bath deposition. • The adsorption and incorporation processes of Sb dopants in ZnO nanowires are detailed in the low- and high pH regions. • The physical properties of Sb-doped ZnO nanowires are investigated by optical spectroscopy. • The piezoelectric coefficients of flexible dynamic strain sensors made of annealed Sb-doped ZnO nanowires are boosted. • The figures-of-merit are compared to conventional piezoelectric materials, showing their high potential for medical devices. [ABSTRACT FROM AUTHOR]

The effect of biaxial strain on crystallographic structure, band gap, polarization, linear and non linear elastic properties of 2D SiC hybrid are studied using ab-initio calculations. The determination of the two critical strain points reveals an elastic region just a little smaller than that of graphene. With load, charge distributions vary and electronic states CBM and VBM undergo a location change. Consequently, enlarging strain reduces the band gap monotonically leading to a semiconductor–metal transition. Debye temperature 407.81 K intermediates between the ones of silicene and germanene. Planar SiC shows a piezoelectric response comparable to 2D buckled compounds materials. The negative sign of the effective non linear modulus reveals an hyperelastic softening behavior of SiC. Under pressure, second order elastic constants show a small anisotropie. The results show that tailoring physical properties of SiC under strain reveals its great potential in the electronic and mechanical devices. [ABSTRACT FROM AUTHOR]

The model of NH3CH2COOH·H2PO3, modified by taking into account the piezoelectric coupling between the ordering structure elements and the strains εi, εj, is used for investigation of the effects that appear under external pressures. Within two-particle cluster approximation, the components of polarization vector and static dielectric permittivity tensor of the mechanically clamped and free crystals, their piezoelectric and thermal characteristics are calculated. The effect of hydrostatic pressure on the phase transition and the calculated physical characteristics of the crystal is studied. A good quantitative description of experimental data for these crystals is obtained. [ABSTRACT FROM AUTHOR]

Effects of La3+ admixture in barium lanthanum titanate (BLT) ceramics system with colossal permittivity on performance of prospective piezoelectric cold plasma application were studied. Usage of cold atmospheric pressure plasma appears promising in terms of industrial and healthcare applications. Performed investigation provide consistent evaluation of doping lanthanum amount on piezoelectric coefficients values with simultaneous capability of charge accumulation for effective plasma generation. Modification of ferroelectric materials with heterovalent ions, however with the lower radii than the original atoms, significantly affects their domain mobility and consequently electromechanical properties. To determine the piezoelectric coefficients, the resonanceantiresonance method was implemented, and values of piezoelectric and dielectric parameters were recorded. Finally the results indicated that addition of 0.4 mol.% of La3+ ions to the ceramic structure maximally increased the values of piezoelectric coefficient to d33 = 20 pC/N and to huge dielectric constant to ε33 T = 29277. [ABSTRACT FROM AUTHOR]

Ferroelectric materials have attracted much interest due to their wide and important technological applications. Regarding their piezoelectric properties, these materials are evaluated by means of relatively complicate global methods. In this work a comparatively simple and efficient local method for the direct estimation of the dij coefficients is presented. The method is based on conventional optical microscopy (OM) and advanced Atomic Force Microscopy (AFM) employed to image the local deformation of a specimen upon variation of a dc electric field. The feasibility and reliability of the method is demonstrated at room temperature in single crystals of (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3. Non-homogeneous electro-mechanical processes are detected. Accordingly, the estimated dij coefficients exhibit a spatial variation over the crystal surface. Except for electro-mechanical systems, the introduced local method could find wide application for the investigation of spatially non-homogeneous properties that possibly exist in relevant magneto-mechanical and thermo-mechanical complex systems. [ABSTRACT FROM AUTHOR]

1D nanostructures of soft ferroelectric materials exert promising potential in the fields of energy harvesting and flexible and printed nanoelectronics. Here, improved piezoelectric properties, energy-harvesting performance, lower coercive fields, and the polarization orientation of poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) nanotubes synthesized with nanoconfinement effect are reported. X-ray diffraction (XRD) patterns of the nanotubes show the peak corresponding to the planes of (110)/(200), which is a signature of ferroelectric beta phase formation. Piezoforce spectroscopy measurements on the free-standing horizontal nanotubes bundles reveal that the effective polarization direction is oriented at an inclination to the long axis of the nanotubes. The nanotubes exhibit a coercive field of 18.6 MV m−1 along the long axis and 40 MV m−1 (13.2 MV m−1 considering the air gap) in a direction perpendicular to the long axis, which is lower than the film counterpart of 50 MV m−1. The poled 200 nm nanotubes, with 40% reduction in poling field, give larger piezoelectric d33 coefficient values of 44 pm V−1, compared to poled films (≈20 pm V−1). The ferroelectric nanotubes deliver superior energy harvesting performance with an output voltage of ≈4.8 V and power of 2.2 μW cm−2, under a dynamic compression pressure of 0.075 MPa at 1 Hz. [ABSTRACT FROM AUTHOR]

Piezoelectric properties, their anisotropy and sound velocity are first studied in the composite based on ferroelectric ZTS-19 ceramic of the PZT type, and the second component of the composite is piezo-passive clay. The composite as a whole is characterised by a specific porosity and elements of various connectivity patterns. The important role of microgeometric factors in the formation of piezoelectric coefficientsd*3j(j = 1 and 3) and their anisotropy ζd3j=d*33/d*31is discussed in terms of connectivity patterns at the volume fraction of clay 0.01 ≤ mcl≤ 0.35. The role of the clay component and clay-containing thin layers in the formation of the piezoelectric activity and sensitivity is interpreted within the framework of models of the two- and three-component composites based on poled ferroelectric ceramics. Results of modelling are compared to experimental data on the studied composite. [ABSTRACT FROM AUTHOR]

Abstract: Aluminum nitride (AlN) reactively sputter deposited from an aluminum target is an interesting compound material due to its CMOS compatible fabrication process and its piezoelectric properties. To obtain high piezoelectric coefficients it is a necessary pre-request to synthesize films with c-axis orientation. Besides the influence of sputter conditions on the microstructure of AlN thin films the condition of the substrate surface is another important factor of utmost importance. In this study, the influence of 350nm thick titanium metallization DC sputter-deposited on SiO2/Si substrates at varying back pressure levels b p,Ti in the range of 2×10−3 to 14×10−3 mbar on the c-axis orientation and the piezoelectric coefficients of 600nm thick AlN thin films is investigated. Besides the plasma power for Ti deposition (P p,Ti =100W) the parameters for AlN synthetization are fixed to P p =1000W and b p,AlN =4×10−3 mbar in 100% N2 atmosphere. Basically, the surface roughness of the Ti bottom layer is the dominating factor resulting either in a high degree of c-axis orientation (i.e. at low b p,Ti values) or in an amorphous AlN microstructure (i.e. at high b p,Ti values). Under low pressure conditions, a smooth and dense surface characteristics is achieved due to a higher kinetic energy associated with the adatoms what is especially important at nominally unheated substrate conditions. The piezoelectric coefficient d 33 decreases from 2.55 to 1.7pm −1 when increasing the titanium sputter pressure from 2×10−3 to 14×10−3 mbar. When decreasing the Ti film thickness to 60nm and hence, reducing the root mean square roughness by a factor of about 2, the intensity associated with the AlN (002) peak is increased by a factor of about 1.7 demonstrating the direct impact. Furthermore, the highest values for d 33 and d 31 (i.e. 3.15pmV−1 and −1.28pmV−1) are determined. [Copyright &y& Elsevier]

Effect of Sr content in lead zirconate titanate PZT ceramic system on performance of piezoelectric transformer application were studied. Our experiments provide consistent evaluation of doping strontium amount on piezoelctric coefficients values and final voltage gain and efficiency of piezoelectric transformer. Extreme values of these parameters are preferred for MEMS device effective driving. Modification of ferroelectric materials with isovalent ions, however with the bigger radii than the original atoms, significantly affects their properties. Particularly the electromechanical coefficients of (PbSr)(ZrTi)O, for mole %'s as x = 0.05, 0.10 and 0.15 ceramics exhibit marked increase, if the PSZT material stoichiometry is near the ferroelectric/relaxor phase boundary. To determine the piezoelectric coefficients, the resonance-antiresonance method was implemented. The results indicated that addition of Sr ions in the amount of 5 mol% in the ceramic structure maximally increased the values of piezoelectric parameter to d = 8.2 pC/N and mechanical quality factor Q = 2902. Finally we demonstrated that in spite of the high piezoelectric coefficients for certain material only the practical examination must be applied in order to draw decisive application conclusions due to the complexity of the double energy conversion in such a specific device as the piezoelectric transformer. [ABSTRACT FROM AUTHOR]

The structure of a novel 1–3-type composite is put forward. It consists of a system of poled ferroelectric ceramic rods surrounded by a ceramic/polymer matrix. The effect of the anisotropy of elastic moduli of the 0–3 matrix on piezoelectric sensitivity and hydrostatic response of the 1–0–3 composite is first analysed. Effective parameters are predicted and analysed for novel composites based on ferroelectric PCR-7M ceramic (PZT type). Examples of significant piezoelectric sensitivity (g*33 ≈ 400 mV·m/N, g* h ≈ 200 mV·m/N), hydrostatic piezoelectric activity (d* h ≈ 350 pC/N) and electromechanical coupling (k* h ≈ 0.45) are discussed. [ABSTRACT FROM PUBLISHER]

A complete set of elastic constants Cij and piezoelectric coefficients eij of a La3Ga5SiO14 (langasite) single crystal was determined from 5.5 to 275.5 K by resonant ultrasound spectroscopy. Unlike a conventional crystal, the elastic constants Cij of the langasite crystal showed three types of temperature dependence: (i) monotonic elastic stiffening upon cooling (C44 and C14); (ii) monotonic elastic softening (C66); and (iii) a stiffening-to-softening transition below 150 K (C11, C12, C13 and C33). In addition, a strong correlation between C66 and the piezoelectric coefficient e11 was confirmed. Group theoretical lattice dynamics analysis revealed that the novel phenomena of elastic softening and strong correlation are explained on the basis of two types of optical mode internal displacements which have the totally symmetric A1 and doubly degenerated E symmetries in the point group D3. [ABSTRACT FROM AUTHOR]

This paper reports results on effective piezoelectric properties of advanced composites based on polydomain relaxor-ferroelectric single crystals of 0.67Pb(Mg1/3Nb2/3)O3 - 0.33PbTiO3. Two variants of the single crystal/porous polymer composite with 0-3-0 connectivity are proposed to study the role of microstructural factors in forming high piezoelectric sensitivity. The effective properties of the related 0-3 single crystal/polymer composite are predicted and considered to show ways of increasing the piezoelectric anisotropy and sensitivity. Examples of the volume-fraction and aspect-ratio dependences of the effective piezoelectric coefficients d3j*, g3j*, the hydrostatic piezoelectric coefficient gh*, and squared figures of merit d33* g33* and dh* gh* of composites are analysed to show in which ranges high piezoelectric sensitivity is attained. The presence of single-crystal polydomain inclusions in the porous 3-0 matrix promotes the large effective parameters (g33* ∼ 103 mV · m/N, gh* ∼ 103 mV · m/N, d33* g33* ∼ 10-10 Pa-1, and dh* gh* ∼ 10-10 Pa-1), and the obvious high-performance advantage of the 0-3-0 composites is discussed taking into account features of their microstructure. [ABSTRACT FROM AUTHOR]

Effective piezoelectric coefficients e33*, d33*, g33*, and h33*, squared figures of merit d33*g33* and dh*gh*, and other related parameters of novel 0-3 and 0-3-0 composites based on single crystals of relaxor-ferroelectric solid solutions of (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 are studied using the effective field method, effective medium method and finite element method. The volume-fraction dependences of a number of parameters and figures of merit are determined using the above methods and compared for composites with aligned prolate spheroidal inclusions. Four parameter ratios that determine interconnections between the effective electromechanical constants of the 0-3-type composites are first introduced. These parameter ratios are used to interpret the longitudinal dielectric and piezoelectric response of composite structures with prolate inclusions that exhibit high piezoelectric activity. The role of piezoelectric anisotropy and activity of the composite components in forming the longitudinal piezoelectric effect is analysed. Specific novel composite architectures with high piezoelectric sensitivity (longitudinal and hydrostatic) are identified and discussed. [ABSTRACT FROM AUTHOR]

Abstract: Aluminium nitride (AlN) reactively sputter-deposited from an aluminium target is an interesting piezoelectric thin film material with high CMOS compatibility. A good c-axis orientation is essential for obtaining high piezoelectric coefficients. Therefore, the influence of different sputtering conditions on the microstructure of AlN thin films with a typical thickness of about 500nm was investigated. In this study it is demonstrated that highly c-axis oriented AlN thin films can be deposited on nominally unheated (100) silicon substrates, most preferentially when using a pure nitrogen atmosphere. The degree of c-axis orientation increases with higher nitrogen concentration and with decreasing the sputtering pressure, whereas the influence of plasma power on the microstructure was found to be negligible. A low sputtering pressure is also useful for minimizing the amount of oxygen contaminations in the deposition chamber and hence for reducing the incorporation of impurities into the AlN films. Intrinsic stress values of AlN thin films were determined by wafer bow measurements and were found to be between −3.5 and 750MPa depending on choice of deposition parameters. Finally, the piezoelectric coefficients d 33 and d 31 were determined experimentally by laser scanning vibrometry in conjunction with a theoretical model. Effective values in c-axis oriented 500nm films with FWHM of 0.33° are 3.0 and −1.0pm/V. For a film of 2.4μm thickness, values of 5.0 and −1.8pm/V were measured, which are near the bulk values. [Copyright &y& Elsevier]

This paper is concerned with the study of effective piezoelectric properties of 1–3 ferroelectric ceramic / polymer composites. The aim of this paper is to show the role of a combination of the electromechanical properties of components and microgeometry of the 1–3 composite in determining its anisotropic piezoelectric response. The system of ceramic rods in the form of elliptic cylinders is an important microgeometric factor that influences the piezoelectric coefficients and their anisotropy. Examples of the piezoelectric response and anisotropy are analysed for the 1–3 composites based on either “soft” or “hard” ceramic and having either piezo-active or piezo-passive matrix. Combinations of the ceramic and polymer components are found that provide different volume-fraction dependences of the piezoelectric coefficients $$ d_{3j}^{*} $$ and $$ g_{3j}^{*} $$: both monotonic, both non-monotonic, monotonic $$ d_{3j}^{*} $$ and non-monotonic $$ g_{3j}^{*} $$, and vice versa. Examples of volume-fraction dependences of electromechanical coupling factors $$ k_{3j}^{*} $$ are also considered. A comparison of the effective piezoelectric coefficients calculated by the effective field method and the finite element method is carried out for different compositions in wide ranges of the ratio of semiaxes of the ellipse and of volume fractions of the components. Good agreement between data calculated by means of the aforementioned methods is obtained for the 1–3 structure comprising the elliptic cylinders. [ABSTRACT FROM AUTHOR]

The effect of the polarisation orientation of [011]-poled polydomain PMN-0.29PT single crystal on the hydrostatic piezoelectric coefficients [image omitted] and [image omitted] of a parallel-connected 2-2 composite has been analysed. Orientation and volume-fraction dependences of the piezoelectric coefficients of the 2-2 PMN-0.29PT/polymer composite have been studied to determine extreme points of [image omitted] and [image omitted] in three cases of rotations of the main crystallographic axes of the PMN-0.29PT single crystal. The largest values of the hydrostatic piezoelectric coefficients [image omitted] = 444 pC/N and [image omitted] = 33.1 C/m2 are of interest for hydroacoustic applications. Important contributions from the piezoelectric coefficients [image omitted] and [image omitted] into [image omitted] and [image omitted], respectively, have been determined near the extreme points of the hydrostatic parameters. [ABSTRACT FROM AUTHOR]

This paper studies polarisation orientation effects in 1-3 composites with two piezo-active components. It is shown how the orientation of the main crystallographic axes in 0.93Pb(Zn1/3Nb2/3)O3-0.07PbTiO3 single-crystal rods and the poling direction of a polyvinylidene fluoride matrix affect the volume fraction behaviour of the piezoelectric coefficients, squared figure of merit and hydrostatic parameters of the composites. For a fixed orientation, effective parameters calculated using the matrix approach are compared with those evaluated by the finite element method. Possible property advantages concerned with orientation effects, maxima of effective parameters and high performance of these composites are analysed taking into consideration the electromechanical properties of the components. [ABSTRACT FROM AUTHOR]

Polyimides are the most promising amorphous piezoelectric polymers not only because of their excellent thermal, mechanical and dielectric properties, but also and, mainly due to their high glass transition temperatures. Here we report on the synthesis of polyimides with one CN (poly2-6) and two CN groups (poly2CN) in the repetition unit, the latter being synthesised for the first time. The dielectric measurements show that remnant polarisation and piezoelectric coefficients values depend strongly on the number of pendant nitrile dipoles in the repetition unit, on the orientation of the backbone anhydride dipole as well as on the imidisation and the poling processes. [ABSTRACT FROM AUTHOR]

The paper deals with the non-linear properties of the piezoelectric ceramics Pb(ZrxTi1 - x)O3 (PZT) at room temperature. The influence of DC electric field on the material parameters, such as piezoelectric coefficients d31 and d33 of PZT ceramics, was studied using the resonance method. The dependence of the resonance and antiresonance frequencies of PZT resonators on DC electric field was measured. Hydrostatic piezoelectric coefficients dh, calculated from d33 and d31 piezoelectric coefficients, were compared with dh coefficients, that were measured directly by dynamic hydrostatic method. Electric field limits for application on PZT ceramics were determined. A remarkable influence of the DC electric field on d31 and d33 piezoelectric coefficients values was exhibited for soft PZT ceramics (APC 850 and APC 856). [ABSTRACT FROM AUTHOR]