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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]

• 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]

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 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]

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]

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]

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]

Abstract: Piezoelectric sensors are usually made of a sensing element compressed between two plates. Therefore, the applied point/distributed load is transferred through these plates to the piezoelectric sensing element. In this sandwich configuration, surface friction has an inevitable and significant impact on the resultant output of the sensor. This paper reports on the influence of the friction on the output of piezoelectric sensing element in a sandwich structure. Although the numerical analysis as well as experiments are performed on the piezoelectric Polyvinylidene Fluoride (PVDF) films, the results are applicable to similar structures with other piezoelectric materials. The results show the remarkable contribution of the friction induced component in the total output for both uniaxial and biaxial PVDF films. The outcome can be used for the optimization of sensor manufacturing processes. In addition, results suggest an alternative new method for the measurement of , the PVDF piezoelectric coefficient in the thickness direction. Alternately, it is possible to use the proposed method in order to accurately measure friction coefficients, particularly for low friction range, namely . [Copyright &y& Elsevier]

Abstract: Knowledge of the electro-active properties of piezoelectric materials is essential for the modeling and design of novel MEMS devices employing the piezoelectric effect. Cantilevers of piezoelectric thin film on Si were fabricated by using sol–gel and photolithograph wafer processing techniques. A scanning laser vibrometer was used to measure the displacement at the contact pad, the first resonant frequency and the tip deflection of the cantilever. The longitudinal (d 33,f), transverse (d 31,f) piezoelectric coefficients, and the Young''s modulus for the piezoelectric thin films were then determined from these results. Finite element analysis (FEA) modeling was carried out to understand the device behaviors and a good agreement has been found between the measurement and the FEA simulated results. [Copyright &y& Elsevier]

Using improved acoustic spectroscopy, we determined the complete above coefficients (16 independent ones) by measuring the macroscopic resonance frequencies of a single lithium-niobate monocrystal. The improvement consisted of using laser-Doppler interferometry for unambiguous vibration-mode identification. Elastic coefficients Cijkℓ agree well with previous reports that used conventional methods. Piezoelectric coefficients eijk agree with the range of four previous reports. Anelastic coefficients Q-1ijkℓ, reported for the first time, suggest that the crystal''s internal friction arises mainly from dislocations, not from intrinsic multiphonon processes. [Copyright &y& Elsevier]

We describe an advanced methodology to determine all the independent elastic-stiffness coefficients Cijkl, the associated internal frictions Qijkl−1, and piezoelectric coefficients eijk of piezoelectric materials from a single monocrystal specimen using resonant-ultrasound spectroscopy with laser-Doppler interferometry. The mechanical-resonance frequencies of a piezoelectric solid depend on all of the elastic and piezoelectric coefficients, and their accurate measurement allows one to determine the elastic and piezoelectric coefficients simultaneously. Resonance-peak-width measurements yield the internal-friction tensor. Successful determination requires correct vibration-mode identification for the observed resonance frequencies. This is achieved unambiguously by measuring deformation distributions on the vibrating-specimen surface with laser-Doppler interferometry and comparing them with calculated displacement distributions. The methodology is applied to lithium niobate (LiNbO3) and langasite (La3Ga5SiO14) crystals. [Copyright &y& Elsevier]

Piezoelectric ceramic/polymer composites with mixed connectivity combine the high values of piezoelectric coefficients of the ferroelectric ceramics and the formability and flexibility of the polymer, making them suitable for in situ acoustic emission (AE) sensors. The present paper reports a study of the piezoelectric and dielectric properties of the ceramic/polymer composite films composed of the calcium modified lead titanate (PTCa) ceramic and the thermoplastic polymer, polyetherketoneketone (PEKK). The mixed connectivity model is used to calculate the percentage of 1–3 connectivity in each composite. Additionally, the sensors were embedded in a carbon fibre reinforced composite (CFRC) and were able to detect simulated AE. [Copyright &y& Elsevier]

Lead-free piezoelectric one-dimensional (1D) nanostructures have exhibited great potential in building biocompatible micro/nano-energy harvesters and self-powered smart sensors. However, their low piezoelectric coefficient still remains as the biggest obstacle for practical applications. In this work, an ultrahigh piezoelectric coefficient with calibrated d 33 from 400 pm V-1 to 814 pm V-1 is achieved in Li-doped (K,Na)NbO 3 (KNLN) lead-free piezoelectric nanorod arrays (NRAs). The giant enhancement on the piezoelectric performance of the KNLN nanorods can be attributed to the manipulation on the phase transition behavior together with the relaxation of strain. The Li+ dopants induce large NbO 6 octahedral distortion and result in the decreased phase transition temperature from orthorhombic (O) to tetragonal (T) phase, which leads to the construction of the O-T phase boundary at room temperature and improves the polarization performance of the products. The ultrahigh piezoelectric performance of the KNLN NRAs gives rise to the remarkably improved energy harvesting performance, which shows highly sensitive pressure sensing behaviors and can be utilized for monitoring the human-body motions. Giant piezoelectric coefficient d 33 up to 814 pm V-1 is achieved in lead-free (K,Na,Li)NbO 3 nanorod arrays by manipulating the orthorhombic-tetragonal phase boundary through A-site Li-doping. The KNLN nanorod arrays exhibit outstanding piezoelectric energy harvesting and pressure sensing performances and realize the self-powered monitoring of human body motions for smart analyzing of the human movement behaviors. [Display omitted] • Li-doped (K,Na)NbO 3 nanorod arrays were grown by hydrothermal process. • Giant piezoelectric coefficient d 33 ~ 814 pm V− 1 is achieved in KNLN nanorod arrays. • Orthorhombic-tetragonal phase boundary of KNLN nanorods is constructed at RT. • The nanogenerators exhibit outstanding energy harvesting and sensing performance. • Self-powered human-body-movements monitoring is realized by KNLN nanogenerators. [ABSTRACT FROM AUTHOR]

The effect of F and H dopants on the structural, elasticothermal and piezoelectric properties of Janus GeC hybrids is studied using ab-initio calculations. The large elastic regions observed reveal a high flexibility of Janus structures. A high rigidity with a hyperelastic softening behavior are observed for this class of materials making them very potential for automotive industry. Configurations where H-atoms decorate C atoms are cork materials. It is also demonstrated that ZA Grüneisen phonon mode are the main responsible of the negative value of thermal expansion. The ultralow thermal conductivity of Janus GeC structures indicate their potential application in thermoelectric devices. Therefore, the strain-engineering of hydro-fluorinated GeC would open a new avenue for potential and novel applications in nano-devices. • Four configurations of Janus (F,H)-GeC hybrids are studied. • The elastic limits and key parameters are determined. • F,H co-decoration leads to a transition from conventional to cork materials. • Janus structures are stiff materials with thermal contraction behavior. • Variable gap, piezoelectric responses and hyperelastic softening are observed. [ABSTRACT FROM AUTHOR]