Cement-based piezoelectret

A cement-based piezoelectret is reported for the first time. Both poling during setting and sodium silicate liquid admixture strengthened the piezoelectret effect. The electret voltage increased upon compressive strain, with partial reversibility; the voltage change was up to 450 V per unit strain (i.e., piezoelectret coupling coefficient up to 4.2 × 10⁻¹⁵ m/V). The effect was relatively strong for a Na⁺ concentration of 0.5 M in the water, in combination with a poling electric field of 225 V/m. The effect increased with increasing magnitude of the constant compressive stress. The direct piezoelectric effect was observed as a minor effect, with the voltage decreasing upon compressive strain; the voltage change was up to 6.7 V per unit strain (i.e., piezoelectric coupling coefficient down to −2.3 × 10⁻¹⁶ m/V). An Na⁺ concentration of 0.5 M gave superior performance than 1.0 M. For 0.5 M, the compressive modulus and piezoelectret coupling coefficient were higher. The poling reduced the compressive modulus and caused pore formation in the vicinity of the electrodes, but it enhanced the piezoelectret effect.     

Large electromechanical anisotropic modified lead titanate ceramics

Dielectric, piezoelectric and mechanical properties of Pb_0.88Ln_0.88(Ti_0.02Mn_0.98)O₃ and Pb_0.76Ca_0.24 ((Co_0.5W_0.5)_0.04Ti_0.96)O₃ ceramics as a function of the tetragonality (c/a) have been investigated. The influence of the poling field on such properties was studied, and it was found that, generally, the electromechanical coupling factor thickness mode,K _t, increases as the poling field was increased reaching a limiting value of 0.47 in the case of samarium-modified lead titanate (PT) (the highest value in the Ln-PT series), and 0.60 in the case of Ca-PT. The coupling factor planar mode,K _p, became zero at 40kVcm^–1 in Ca-PT, and almost zero in the case of Sm-PT at 60 kV cm^–1. In the other members of Ln-PT,K _p was lower than 10 to 15%. It was suggested that both the grain size and the 90° domain rotation, caused as a consequence of the strong poling field, could explain such a phenomenon.     

Influence of Electric Poling on Pb0.9Bi0.1Fe0.55Nb0.45O3 Multiferroic

This paper analyzes the influence of electric poling on structure, magnetism, and ferroelectricity by temperature-dependent Raman scattering (180 K–500 K), magnetic susceptibility, and ferroelectric measurements on Pb_0.9Bi_0.1Fe_0.55Nb_0.45O₃ (PBFNO) multiferroic. X-ray diffraction (XRD) has confirmed the monoclinic structure for PBFNO sample before and after poling. Rietveld refined XRD for poled and unpoled sample shows the influence of electric poling on Fe-O1, Fe-O2, Nb–O, and Bi-O modes with small variation in the lattice parameters. The unpoled PBFNO exhibits broad and overlapping 10 active modes at room temperature (100 to 1300 cm^?1) at 147, 212, 255, 431, 479, 561, 700, 795, 835, and 1112 cm^?1. In case of a poled sample, Pb–O and Nb–O-Nb modes become more active compared to the unpoled sample. Changes observed in the temperature-dependent magnetic measurements, i.e., ZFC/FC and M-H loop, evidence the poling effects on Fe–O and Nb–O active modes. By poling the improvement in ferroelectric domain, ordering occurs, and it is confirmed by P-E loops. The consequences of numerous investigations on electric poling of PBFNO will provide the foundation for future device development and design.

     

Influence of poling conditions on the piezoelectric properties of PZT ceramics

The influence of the poling temperature, the poling electric field, the poling time and the distance between electrodes on the dielectric constant _r and the electro-mechanical coupling factor k_r of PZT were investigated using a statistical analysis method. Interactions between various factors affecting _r and k_r parameters were found particularly, with regard to the poling temperature. The k_r value of PZT is influenced more by the absolute voltage than by the applied electric field strength.     

Correlation between spin–phonon coupling and magneto-electric effects in CoFe2O4/PMN-PT nanocomposite: Raman spectroscopy and XMCD study

We have investigated strain-induced spin lattice coupling in the CoFe₂O₄/0.65Pb (Mg_1/3Nb_2/3)O₃–0.35PbTiO₃(PMN-PT) composite system, evident by temperature-dependent Raman spectroscopy and magnetization measurements. The strain interactions lead to magneto-electric coupling, and the measured magneto-electric voltage coefficient is 40 mV/cm^?1Oe^?1 for the CoFe₂O₄/PMN-PT composite samples. X-ray magnetic circular dichroism (XMCD) analysis establishes modified spin structure in the electrically poled CoFe₂O₄/PMN-PT composite, further validating the coupling between magnetic and electric ordering in the composite. The magneto-electric coupling coefficient α vs dc magnetic field curves revealed hysteretic behavior and enhanced α values after electric poling, which originates from the strain-induced modifications in the magnetic structure of composite in the electrically poled samples. These findings suggest that the existence of spin lattice coupling may lead to the mechanism of strong magneto-electric effects via strain interactions in CoFe₂O₄/PMN-PT composite.

     

0-3型压电陶瓷-硫铝酸盐水泥复合材料的压电性能

采用压制成型法,以快硬硫铝酸盐水泥为基体制备了水泥基压电复合材料。分析讨论了极化工艺条件和PZT含量对水泥基压电复合材料压电性的影响。结果表明,较高的极化电场强度和较长的极化时间均有利于压电性能的提高,但当极化电场强度和极化时间达到4.0 kV/mm和45 min后,压电应变常数d₃₃趋于稳定; 随着PZT含量的增加,硫铝酸盐水泥基压电复合材料的压电应变常数d₃₃、压电电压常数g₃₃和机电耦合系数K_P、K_t均显著增大。当PZT质量分数达到85%时,K_P和K_t可达28.54%和28.19%。      

Microstructure study of Sm,Mn-modified PbTiO3 piezoelectric ceramics by XRD profile-fitting technique

By using the X-ray diffraction profile-fitting technique, the microstructures of Sm, Mn-modified PbTiO₃ piezoelectric ceramic discs, including ferroelectric domain sizes, microstrains, and their variations with the poling strength have been quantitatively investigated. The results manifest that the modified PbTiO₃ ceramics contain a high density of domain walls due to the presence of finely-divided coherent domain structures (tens of nanometres in dimension). The poling treament can evidently influence the domain-size distribution, with a more homogeneous microstructure being developed; however, it simultaneously causes high anisotropic microstrains within the structure which, together with the high density of domain walls, is expected to be responsible for the unusual high electromechanical coupling properties possessed by this material.     

Modeling of poling behavior of ferroelectric 3–3 composites

Piezoelectric 3–3 composites are often prepared from unpoled PZT ceramics and polymer matrices. During the poling process the PZT cannot deform freely due to the clamping by the surrounding polymer, which after poling results in the occurrence of residual mechanical stress in the composite. Based on the multi-linear constitutive model of ferroelectric and ferroelastic piezoceramics, a nonlinear finite element analysis was performed within the representative volume element to model the poling behavior of this kind of composites, in which appropriate periodic boundary conditions were prescribed for the displacements and the electric field of the composites. Considering the fact from experimental data that changes of the remanent strain induced by the switching process are volume preserving, we introduced different criteria in evaluating the maximum and minimum values of the ferroelastic strain S^f. A numerical simulation was then conducted to investigate the effects of different poling voltages and volume fractions of the PZT ceramic on the distribution of residual mechanical stress in the PZT of composites. The results show that if V_f < 18% a portion of the compressive mechanical stress in the poling direction on the PZT ceramic may cause a mechanical depolarization of the PZT ceramic.     

Composition dependence of thermally induced second-harmonic generation in chalcohalide glasses

By investigating the second-harmonic generation (SHG) of the series (100 − 2x)GeS₂·xGa₂S₃·xPbI₂ (x = 5, 10, 15, and 20) chalcohalide glass samples after thermal poling, it was found that there was an optimal poling temperature for each composition and there was also a relation between optimal poling temperature and glass transition temperature. With increasing x, the obtained second-order susceptibility χ⁽²⁾ shows an increase first and then decrease, and the maximum was seen at x = 15. A dipole reorientation model and structural relaxation causing by Ga₂S₃ and PbI₂ were proposed to explain the dependence of poling temperature on SH intensity for each composition and the presence of the maximum χ⁽²⁾ in this chalcohalide glass series.     

Ageing of (Pb,La)(Zr,Ti)O3 ferroelectric ceramics and the space charge arising on hot poling

Polarization-temperature diagrams of pyroelectric charge and the decrease of remanent polarization (P _R) at constant temperature are investigated in PLZT 8/65/35 ceramic samples. The arousal of space charge is shown to be unlike that of pyroelectric charge and highly dependent on poling temperature. This charge, measured by the thermally stimulated current in hot poled samples, obeys the dielectric discharge lawi=kt ^–n and is also responsible for the recovery ofP _R after the samples have been thermically depoled in part, in contrast with samples poled at room temperature. The evolution ofP _R follows the lawi =kt ^-n Int where the slopeB decreases with poling temperature when the sign ofP _R is that of the former polarization. The ageing behaviour is correlated with the space charge that arises on hot poling.     

Giant increase of the second harmonic radiation's absorption during optical poling of oxide glass

Abstract

A giant reversible growth (≥ 10³ times) of the absorption of second harmonic radiation by optical poling of oxide glass was discovered. The observed absorption exerts an influence on the optical poling process and leads to a restriction of the maximum value of the photoinduced second harmonic generation in oxide glass. A theoretical model of the observed phenomenon is given. The growth of absorption is considered as a result of special anharmonic electron-phonon interactions caused by photoinduced electrostricted phonons. Exploration of the total absorption indicates that the effects of photodarkening do not play a key role in the observed phenomena.     

Sol-gel process of non-linear optical silica films with organic chromophore as side chain

A transparent silica film with organic chromophore, Disperse Red 1(DR1), as side chain was prepared in this study by the sol-gel process. Next, the film was baked at 120 °C with corona discharge poling. The resulting films exhibited a second harmonic response,d ₃₃=46 pmV^?1. High poling stability was observed when the film was maintained at 60 °C. The effects of HCl concentration on the molecular orientation and the thermal stability of the specimens were also investigated.     

Poling process and piezoelectric properties of lead zirconate titanate/sulphoaluminate cement composites

The sulphoaluminate cement was, for the first time, used to fabricate 0-3 piezoelectric composites by compressing technique. The dependences of piezoelectric properties of composites on poling conditions, particle size and contents of Lead Zirconate Titanate (PZT) were discussed especially. The results show that the piezoelectric properties of composites are improved by increasing poling field E, poling time t and poling temperature t. The optimum E, t and T are 4.0 kV/mm, 45 min and 120°C respectively in this work. The piezoelectric strain factor d₃₃ is found to increase with increasing particle size of PZT. When the particle size of PZT is larger than about 130 m, the d₃₃ is nearly independent of particle size. The d₃₃, g₃₃ and the electromechanical coupling coefficient K _p, K _t of composites increase rapidly with increasing content of PZT. When the content of PZT reaches 85%, K _p and K _t are 28.54 and 28.19%, respectively.     

Synergy-Compensation Effect of Ferroelectric Polarization and Cationic Vacancy Collaboratively Promoting CO2 Photoreduction

Photocatalytic CO₂ reduction is severely limited by the rapid recombination of photo-generated charges and insufficient reactive sites. Creating electric field and defects are effective strategies to inhibit charge recombination and enrich catalytic sites, respectively. Herein, a coupled strategy of ferroelectric poling and cationic vacancy is developed to achieve high-performance CO₂ photoreduction on ferroelectric Bi₂MoO₆, and their interesting synergy-compensation relationship is first disclosed. Corona poling increases the remnant polarization of Bi₂MoO₆ to enhance the intrinsic electric field for promoting charge separation, while it decreases the CO₂ adsorption. The introduced Mo vacancy (V_Mo) facilitates the adsorption and activation of CO₂, and surface charge separation by creating local electric field. Unfortunately, V_Mo largely reduces the remnant polarization intensity. Coupling poling and V_Mo not only integrate their advantages, resulting in an approximately sevenfold increased surface charge transfer efficiency, but also compensate for their shortcomings, for example, V_Mo largely alleviates the negative effects of ferroelectric poling on CO₂ adsorption. In the absence of co-catalyst or sacrificial agent, the poled Bi₂MoO₆ with V_Mo exhibits a superior CO₂-to-CO evolution rate of 19.75 µmol g⁻¹ h⁻¹, ≈8.4 times higher than the Bi₂MoO₆ nanosheets. This work provides new ideas for exploring the role of polarization and defects in photocatalysis.     

Pyroelectric behaviour of laser-evaporated poly(vinyl fluoride) films

Laser-evaporated poly(vinyl fluoride) films were prepared with a view to their use as pyroelectric sensing elements. A high power (60 W) CO₂ laser was employed to prepare these films (0.1–1 microm thick) in a vacuum of better than 1 × 10^?5Torr. The films were characterized by determining their structure and molecular weight using IR spectroscopy and mass spectrometry. The pyroelectric currents developed in these films by poling them in electric fields of strength (1–5) × 10⁵ V cm^?1 and at poling temperatures of 303–450 K were measured. Various metal electrodes were used and the effect of the electrode material on the pyroelectric activity was also studied. The results are used to interpret the origin of the pyroelectricity in these films. The experimental details of the preparation of the films, their characterization and the pyroelectric current measurements are discussed.     

A Light Harvesting,Self‐Powered Monolith Tactile Sensor Based on Electric Field Induced Effects in MAPbI3 Perovskite

Organolead trihalide perovskite MAPbI₃ shows a distinctive combination of properties such as being ferroelectric and semiconducting, with ion migration effects under poling by electric fields. The combination of its ferroelectric and semiconducting nature is used to make a light harvesting, self‐powered tactile sensor. This sensor interfaces ZnO nanosheets as a pressure‐sensitive drain on the MAPbI₃ film and once poled is operational for at least 72 h with just light illumination. The sensor is monolithic in structure, has linear response till 76 kPa, and is able to operate continuously as the energy harvesting mechanism is decoupled from its pressure sensing mechanism. It has a sensitivity of 0.57 kPa^?1, which can be modulated by the strength of the poling field. The understanding of these effects in perovskite materials and their application in power source free devices are of significance to a wide array of fields where these materials are being researched and applied.     

Poling field versus piezoelectric property for [001]<Subscript><Emphasis Type="Italic">c</Emphasis></Subscript> oriented 91%Pb(Zn<Subscript>1/3</Subscript>Nb<Subscript>2/3</Subscript>)O<Subscript>3</Subscript>–9%PbTiO<Subscript>3</Subscript> single crystals

Electromechanical property measurements and microstructure observations using optical microscopy were performed on a [001] _c oriented k ₃₃ resonator made of 91%Pb(Zn_1/3Nb_2/3)O₃–9%PbTiO₃ single crystal, which was polarized under different electric fields. At room temperature, when the poling field is 1100 V/mm, the electromechanical coupling factor k ₃₃ is 0.90 and piezoelectric coefficient d ₃₃ is 1665 pC/N. Such superior electromechanical properties could be attributed to the formation of monoclinic multi-domain structure, which transforms to tetragonal phase at 46 °C. While at a higher poling field of 1200 V/mm, the crystal becomes single-domain tetragonal state and its k ₃₃ and d ₃₃ are only about 0.69 and 850 pC/N, respectively. The critical poling field to transform the monoclinic phase to the tetragonal phase is found to be ~1120 V/mm.     

Genetically Induced In Situ‐Poling for Piezo‐Active Biohybrid Nanowires

Polycrystalline piezo‐active materials only exhibit a high macroscopic piezoresponse if they consist of particles with oriented crystal directions and aligned intrinsic dipole moments. For ferroelectric materials, the postsynthesis alignment of the dipoles is generally achieved by electric poling procedures. However, there are numerous technically interesting non‐ferroelectric piezo‐active materials like zinc oxide (ZnO). These materials demand the alignment of their intrinsic dipoles during the fabrication process. Therefore, in situ‐poling techniques have to be developed. This study utilizes genetically modified M13 phage templates for the generation of force fields, which directly control the ZnO dipole poling. By genetic modification of M13 phage template, the piezoelectric response of the ZnO/M13 phage hybrid nanowire is doubled compared to the hybrid nanowire based on unmodified M13 wild type (wt) phage templates. Thus, the formation of piezo‐active domains consisting of oriented ZnO nanocrystals is directly induced by the genetic modification. By the combination of the fiber‐like structure of individual M13 phages with the bioenhanced electromechanical properties of ZnO, hybrid nanowires with a length of ≈1.1 µm and a thickness of ≈63.5 nm are fabricated with a high piezoelectric coefficient of up to d₃₃ = 7.8 pm V^?1 for genetically modified M13 phage templates.     

A pronounced manifestation of a new electric-to-mechanical coupling phenomenon in the ferroelectric ceramic PZT 65/35

Summary In this paper, we present experimental results to show a pronounced manifestation of a new electric-to-mechanical coupling phenomenon in the ferroelectric ceramic PZT 65/35. This phenomenon has been previously reported in the electro-optic ceramic PLZT 7/65/35. We believe that it is also present in other ferroelectric materials. In particular, experimental evidence indicates that this coupling phenomenon during the process of poling results in flexural mechanical displacements which are much larger than the combined changes in thickness due to domain switching and conventional piezoelectric coupling. Its influence also increases markedly with remanent polarization.With 1 FigureThis paper is dedicated to the memory of Professor Aris Phillips whom I have had the extreme privilege of knowing.     

Ultraviolet-assisted cold poling of Pb(Zr<Subscript>0.52</Subscript>Ti<Subscript>0.48</Subscript>)O<Subscript>3</Subscript> films

This paper discusses the advantages of a room-temperature poling procedure during exposure to ultraviolet light for Pb(Zr_0.52Ti_0.48)O₃ (PZT) films. The results of these experiments include the following: for 1.7-µm-thick chemical solution-deposited PZT films, the saturation photocurrent density after a 10 min white light exposure (190–1900 nm) (no DC bias field applied) increased up to 0.066 µA/cm² with increasing Cr thickness of top electrode in Cr/Pt bilayer electrodes. Furthermore, the d_33,f piezoelectric coefficients for UV-poled samples were 40 and 20% higher than those achieved from field-only poling at either room temperature or 150 °C. Additionally, the development of an internal bias field and pinching were investigated in major and minor polarization–electric field loops. It was found that ultraviolet illumination during the poling process produced photoinduced charge carriers that became trapped by local defects and/or grain boundaries in the films.