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Pyroelectric materials, with piezoelectricity and pyroelectricity, have been widely used in infrared thermal detectors. In this paper, a modified first-order plate theory is extended to analyze a pyroelectric sensitive element structure. The displacement, temperature, and electric potential expand along the thickness direction. The governing equation of the pyroelectric plate is built up. The potential distributions with upper and lower electrodes are obtained under different supported boundary conditions. The corresponding numerical results of electric potential are consistent with those obtained by the three-dimensional finite element method. Meanwhile, the theoretical results of electric potential are close to that of experiments. The influence of supported boundary conditions, piezoelectric effect, and plate thickness are analyzed. Numerical results show that the piezoelectric effect reduces the electric potential. The thickness of the pyroelectric plate enhances the electric potential but reduces the response speed of the detector. It is anticipated that the pyroelectric plate theory can provide a theoretical approach for the structural design of pyroelectric sensitive elements. [ABSTRACT FROM AUTHOR]

Design of pyroelectric crystals decoupled from piezoelectricity is not only a topic of scientific curiosity but also demonstrates effects in principle that have the potential to be technologically advantageous. Here we report a new method for the design of such materials. Thus, the co‐doping of centrosymmetric crystals with tailor‐made guest molecules, as illustrated by the doping of α‐glycine with different amino acids (Threonine, Alanine and Serine). The polarization of those crystals displays two distinct contributions, one arising from the difference in dipole moments between guest and host and the other from the displacement of host molecules from their symmetry‐related positions. These contributions exhibit different temperature dependences and response to mechanical deformation. Thus, providing a proof of concept for the ability to design pyroelectric materials with reduced piezoelectric coefficient (d22) to a minimal value, below the resolution limit of the method (<0.005 pm/V). [ABSTRACT FROM AUTHOR]

Organic and metal-free molecules with piezoelectric and ferroelectric properties have gained wide interest for their applications in the domain of mechanical energy harvesting due to their desirable properties such as light weight, thermal stability, mechanical flexibility, feasibility to achieve high Curie temperatures, and ease of synthesis. However, the understanding and design of these materials for piezoelectric energy harvesting applications is still in its early stages. This review paper presents a comprehensive overview of the fundamental characterization of piezoelectricity for a range of organic ferro- and piezoelectric materials and their composites. It also discusses the limitations of traditional piezoelectric materials and highlights the advantages of organic materials in this area in the introduction part. In addition, the paper provides a detailed description of peptide-based and other biomolecular piezoelectric materials as a bio-friendly alternative to current materials. This perspective aims to guide researchers in designing functional organic materials and composites for practical mechanical energy harvesting applications and to highlight current limitations and future perspectives in this emerging area of research. [ABSTRACT FROM AUTHOR]

Piezoelectric photocatalysis can effectively suppress the recombination of electron holes during the course of photocatalysis, which has been widely applied in environmental and energy catalysis. Its advantage is that when the piezoelectric effect happens, a built-in electric field is formed inside the catalyst, which improves the separation efficiency of photogenerated charge carriers and obtains more excellent photocatalytic performance. The efficient conversion of mechanical energy to chemical energy can be realized through the synergistic effect of the piezoelectric effect, and photocatalysis is greatly significant in solving the energy crisis and providing environmental protection. Therefore, we organized a more complete review to better understand the mechanism and system of piezoelectric photocatalysis. We briefly introduce the principle of the piezoelectric effect, the existing types of piezoelectric photocatalysts, the practical application scenarios, and the future challenges and feasible methods to improve catalytic efficiency. The purpose of this review is to help us broaden the idea of designing piezoelectric photocatalysts, clarify the future research direction, and put it into more fields of environmental protection and energy reuse. [ABSTRACT FROM AUTHOR]

This work embarks on an exploration of piezoelectric energy harvesting (PEH), seeking to unravel its potential and practicality. PEH has emerged as a promising technology in the field of civil engineering, offering a sustainable approach to generating energy from ambient mechanical vibrations. We will explore the applications and advancements of PEH within the realm of civil engineering, focusing on publications, especially from the years 2020 to 2024. The purpose of this study is to thoroughly examine the potential and practicality of PEH in civil engineering applications. It delves into the fundamental principles of energy conversion and explores its use in various areas, such as roadways, railways, bridges, buildings, ocean wave-based energy harvesting, structural health monitoring, and even extraterrestrial settings. Despite the potential benefits of PEH in these domains, there are significant challenges that need to be addressed. These challenges include inefficient energy conversion, limitations in scalability, concerns regarding durability, and issues with integration. This review article aims to address these existing challenges and the research gap in the piezoelectric field. [ABSTRACT FROM AUTHOR]

The inevitable feedback between the environmental and energy crisis within the next decades can probably trigger and/or promote a global imbalance in both financial and public health terms. To handle this difficult situation, in the last decades, many different classes of materials have been recruited to assist in the management, production, and storage of so-called clean energy. Probably, ferromagnets, superconductors and ferroelectric/piezoelectric materials stand at the frontline of applications that relate to clean energy. For instance, ferromagnets are usually employed in wind turbines, superconductors are commonly used in storage facilities and ferroelectric/piezoelectric materials are employed for the harvesting of stray energy from the ambient environment. In this work, we focus on the wide family of ferroelectric/piezoelectric materials, reviewing their physical properties in close connection to their application in the field of clean energy. Among other compounds, we focus on the archetypal compound Pb(Zr,Ti)O3 (or PZT), which is well studied and thus preferred for its reliable performance in applications. Also, we pay special attention to the advanced ferroelectric relaxor compound (1−x)Pb(Mg1/3Nb2/3)O3−xPbTiO3 (or PMN-xPT) due to its superior performance. The inhomogeneous composition that many kinds of such materials exhibit at the so-called morphotropic phase boundary is reviewed in connection to possible advantages that it may bring when applications are considered. [ABSTRACT FROM AUTHOR]

Perovskite materials have advanced significantly in the last several years, putting them at the forefront of research on energy harvesting, due to their remarkable piezoelectric, structural, electric, and optoelectronic properties. Enormous efforts have been made by various researchers to explore ABO3 perovskite symmetry by playing with a variety of cations at the A and B sites. With an emphasis on the wide range of uses for perovskites in energy harvesting, this abstract offers a succinct summary of the most recent advancements in the field. Interestingly, perovskite solar cells have proven they can be widely used in the solar energy industry by reaching previously unheard-of levels of stability and efficiency. Perovskites are versatile and show their many uses outside of photovoltaics, such as in thermoelectric devices and light-emitting diodes. This article also explores the electronic and structural characteristics of perovskites that enable effective energy conversion. Their compositions can be adjusted to create materials with specific properties, leading to increased functionality and better performance. Herein, the crystal structure and intriguing properties of perovskite materials including dielectric, piezoelectric, ferroelectric, magneto resistance, and superconductivity have been discussed. Perovskite-based devices are also economically feasible choices for renewable energy technologies due to their low-cost manufacturing processes. It has been reported that perovskite materials are worthy materials for use in optoelectronic devices, transducers, ultrasonic devices, solid oxide fuel cells, ceramics, non-volatile memories, thin film capacitors, etc. [ABSTRACT FROM AUTHOR]

This study describes the synthesis and characterization of the lead-free organic ferroelectric perovskite N-methyl-N'-diazabicyclo [2.2.2]octonium)-ammonium trichloride (MDABCO-NH4Cl3). The electrospinning technique was employed to obtain nanofibers embedded with this perovskite in a PVC polymer for hybrid fiber production. The dielectric, piezoelectric, and pyroelectric properties of these fibers were carefully examined. Based on measurements of the dielectric permittivity temperature and frequency dependence, together with the pyroelectric results, a transition from a high temperature paraelectric to a ferroelectric phase that persisted at room temperature was found to occur at 438 K. The measured pyroelectric coefficient yielded values as high as 290 μC K−1 m−2, which is in between the values reported for MDABCO-NH4I3 and the semiorganic ferroelectric triglycine sulfate (TGS). The hybrid nanofibers exhibited good morphological characteristics and demonstrated very good piezoelectric properties. Specifically, a piezoelectric coefficient of 42 pC/N was obtained when applying a periodical force of 3 N and a piezoelectric voltage coefficient of geff = 0.65 V mN−1. The performance of these fibers is on par with that of materials discussed in the existing literature for the fabrication of nano energy-harvesting generators. Importantly, the perovskite nanocrystals within the fibers are protected from degradation by the surrounding polymer, making them a promising environmentally friendly platform for flexible mechanical energy harvesting. [ABSTRACT FROM AUTHOR]

It is now well reported that the coatings of graphene/candle soot/black carbon can improve the performance of pyroelectric materials. Herein, the performance of candle soot‐coated pyroelectric material (piezoelectric buzzer) under solar heating is reported. To compare the performance, coated/uncoated piezoelectric buzzers are exposed to solar light as well as IR lamp separately. Piezoelectric buzzer shows multiple times superior performance after coating of candle soot. The open‐circuit voltage improves five times with a peak voltage of 3.31 V in solar light. The comparative enhancement in short‐circuit pyroelectric current is four times with a peak current of 2.73 μA. Also, the power and energy densities show multifold enhancement after coating. [ABSTRACT FROM AUTHOR]

Tailoring the surface morphology of nanofibers determines its application to an excessive extent. At present, different structures of nanofibers have been produced such as wrinkled, grooved, porous, rough, etc. Amongst them, wrinkled nanofibers have attracted the attention of researchers due to their exceptional structure and properties such as coarse surface, high surface energy, high specific surface area, excellent mechanical properties, and good piezoelectricity resulting in serving successfully in various fields such as energy harvesting, air filtration, water filtration, gas sensors, biomedical applications, fuel cells, and energy storage. Therefore, this work aims to spotlight the importance of the wrinkled structure, methods, and strategies used for producing electrospun wrinkled nanofibers of various materials. This review focuses on the materials, preparation methods, and applications of the electrospun wrinkled nanofibers. This review can serve as an essential reference for the materials, formation methods, and applications of wrinkled nanofibers prepared via electrospinning. [ABSTRACT FROM AUTHOR]

In this paper, the well-established two-dimensional mathematical model for linear pyroelectric materials is employed to investigate the reflection of waves at the boundary between a vacuum and an elastic, transversely isotropic, pyroelectric material. A comparative study between the solutions of (a) classical thermoelasticity, (b) Cattaneo-Lord-Shulman theory and (c) Green-Lindsay theory equations, characterised by none, one and two relaxation times, respectively, is presented. Suitable boundary conditions are considered in order to determine the reflection coefficients when incident elasto-electro-thermal waves impinge the free interface. It is established that, in the quasi-electrostatic approximation, three different classes of waves: (1) two principally elastic waves, namely a quasi-longitudinal Primary ( qP) wave and a quasi-transverse Secondary ( qS) wave; and (2) a mainly thermal ( qT) wave. The observed electrical effects are, on the other hand, a direct consequence of mechanical and thermal phenomena due to pyroelectric coupling. The computed reflection coefficients of plane qP waves are found to depend upon the angle of incidence, the elastic, electric and thermal parameters of the medium, as well as the thermal relaxation times. The special cases of normal and grazing incidence are also derived and discussed. Finally, the reflection coefficients are computed for cadmium selenide observing the influence of (1) the anisotropy of the material, (2) the electrical potential and (3) temperature variations and (4) the thermal relaxation times on the reflection coefficients. [ABSTRACT FROM AUTHOR]

The main focus of current attempts at sustainable energy development and environmental remediation is on using catalysts to directly transform primary energy (solar, mechanical, and thermal energies) from the surrounding environment into chemical energy. However, the strong charge recombination is a major factor in why the presently available catalysts are not up to par in their catalytic effectiveness. The creation of polarization electric fields has emerged as one of the most successful solutions to this issue. This review focuses on the principles of the piezoelectric effect in ferroelectric, piezoelectric, and pyroelectric materials, the mechanism of piezoelectric catalysis and piezoelectric photocatalysis, and the integration of polarization electric field and semiconductor properties to promote the separation of electron-hole pairs and regulate the charge migration process in the bulk phase. Based on the comparison and classification of different structure types of piezoelectric catalysts and piezoelectric photocatalysts in low dimensions, optimization techniques to improve piezoelectric properties and catalytic activities were introduced and the latest progress of polarization-facilitated piezoelectric catalysis/piezoelectric photocatalysis in the polarization electric field of renewable energy production and environmental remediation was overviewed. Finally, we outlined the significant obstacles and possible alternatives for designing polarization-enhanced strategies that make use of efficient energy harvesting. [Display omitted] • The piezoelectric and piezo-photoelectric effects were summarized and categorized. • Enhancement strategies towards improving polarization electric field were discussed. • The low- dimensional piezoelectric catalysts and piezoelectric photocatalysts were reviewed. • Challenges and prospects of piezoelectric catalyst and piezoelectric photocatalyst were outlined. [ABSTRACT FROM AUTHOR]

Pyroelectric materials, with piezoelectricity and pyroelectricity, have been widely used in infrared thermal detectors. In this paper, a modified first-order plate theory is extended to analyze a pyroelectric sensitive element structure. The displacement, temperature, and electric potential expand along the thickness direction. The governing equation of the pyroelectric plate is built up. The potential distributions with upper and lower electrodes are obtained under different supported boundary conditions. The corresponding numerical results of electric potential are consistent with those obtained by the three-dimensional finite element method. Meanwhile, the theoretical results of electric potential are close to that of experiments. The influence of supported boundary conditions, piezoelectric effect, and plate thickness are analyzed. Numerical results show that the piezoelectric effect reduces the electric potential. The thickness of the pyroelectric plate enhances the electric potential but reduces the response speed of the detector. It is anticipated that the pyroelectric plate theory can provide a theoretical approach for the structural design of pyroelectric sensitive elements.

Ferroelectricity in biological system has been anticipated both theoretically and experimentally over the past few decades. Claims of ferroelectricity in biological systems have given rise to confusion and methodological controversy. Over the years, a "loop" of induced polarization in response to a varying applied electrical field and a consequent polarization reversal has prompted many researchers to claim ferroelectricity in biological structures and their building blocks. Other observers were skeptical about the methodology adopted in generating the data and questioned the validity of the claimed ferroelectricity as such, "loop" can also be obtained from linear capacitors. In a paper with somewhat tongue-in-cheek title, Jim Scott showed that ordinary banana peels could exhibit closed loops of electrical charge which closely resemble and thus could be misinterpreted as ferroelectric hysteresis loops in barium sodium niobate, BNN paraphrasing it as "banana". In this paper, we critically review ferroelectricity in biological system and argue that knowing the molecular and crystalline structure of biological building blocks and experimenting on such building blocks may be the way forward in revealing the "true" nature of ferroelectricity in biological systems. [ABSTRACT FROM AUTHOR]

Piezoelectric materials have drawn significant attention from researchers in the recent past as the piezo-potential, induced by applied external stress, generates an electric field, which paves the way for the creation and transfer of electrons and holes. After the theoretical prediction of the existence of the piezoelectric effect in transition metal dichalcogenides (TMDCs) semiconductors, intense research efforts have been made by various researchers to demonstrate the effect experimentally. In addition 2D TMDCs exhibit layer-dependent tunable electronic structure, strongly bound excitons, enhanced catalytic activity at their edges, and novel spin/pseudospin degrees of freedom. The edge sites and activated basal planes of 2D TMDCs are shown to be highly active toward catalysis of the hydrogen evolution reaction (HER). However, as compared to electrocatalytic or even photocatalytic performances, TMDC materials exhibit poorer piezocatalytic activity, in general. Therefore, a numbers of research strategies have been made to intensify the piezoelectric effect by synthesizing different types of TMDC nanostructures, by coupling the piezoelectric effect with the photocatalytic effect, by doping with other materials, etc. This review discusses various techniques of synthesis of TMDCs nanostructures and the recent progresses in applications of TMDC nanomaterials in piezocatalysis. In the present article, the piezocatalytic dye degradation performances and HER activity using different TMDCs have been reviewed in detail. Different methods of increasing the piezocatalytic activity of various TMDCs nanostructures have been illustrated. Here, it has also been attempted to systematically summarize and provide an outlook of the charge transfer behaviour and catalytic mechanisms in large varieties of TMDC piezocatalysts and piezo-photocatalysts. In addition, advanced applications of TMDC piezocatalytic materials as piezoelectric nanogenerator, piezocatalytic dye degradation, piezo−phototronic dye degradation and HER studies have been highlighted. [ABSTRACT FROM AUTHOR]

Complex oxides exhibit a wide range of fascinating functionalities, such as ferroelectricity, piezoelectricity, and pyroelectricity, which are indispensable for cutting‐edge electronics, energy, and information technologies. The intriguing physical properties of these complex oxides arise from the complex interplay between lattice, orbital, charge, and spin degrees of freedom. Here, it is reviewed how electromechanical properties can be achieved/improved by artificially breaking the symmetry of centrosymmetric oxides via engineering thermodynamic variables such as stress, strain, electric field, and chemical potentials. The mechanisms that have been utilized to break the inherent symmetry of conventional materials that lead to novel functionalities and applications are explored. It is highlighted that access to "hidden phases," which otherwise are prohibited, could uncover opportunities to host exotic properties, such as piezoelectricity, pyroelectricity, etc. This review not only reports how to engineer intrinsically nonpolar and centrosymmetric oxides for emergent properties, but also has implications for manipulating polar functional materials for better performance. [ABSTRACT FROM AUTHOR]

Ferroelectric switching is unambiguously demonstrated for the first time in a III-V semiconductor based material: Al1-xScxN—A discovery which could help to satisfy the urgent demand for thin film ferroelectrics with high performance and good technological compatibility with generic semiconductor technology which arises from a multitude of memory, micro/nano-actuator, and emerging applications based on controlling electrical polarization. The appearance of ferroelectricity in Al1-xScxN can be related to the continuous distortion of the original wurtzite-type crystal structure towards a layered-hexagonal structure with increasing Sc content and tensile strain, which is expected to be extendable to other III-nitride based solid solutions. Coercive fields which are systematically adjustable by more than 3 MV/cm, high remnant polarizations in excess of 100 μC/cm2—which constitute the first experimental estimate of the previously inaccessible spontaneous polarization in a III-nitride based material, an almost ideally square-like hysteresis resulting in excellent piezoelectric linearity over a wide strain interval from −0.3% to + 0.4% and a paraelectric transition temperature in excess of 600 °C are confirmed. This intriguing combination of properties is to our knowledge as of now unprecedented in the field of polycrystalline ferroelectric thin films and promises to significantly advance the commencing integration of ferroelectric functionality to micro- and nanotechnology, while at the same time providing substantial insight to one of the central open questions of the III-nitride semiconductors—that of their spontaneous polarization. [ABSTRACT FROM AUTHOR]

As a consequence of rapid industrialization throughout the world, various environmental pollutants have begun to accumulate in water, air, and soil. This endangers the ecological environment of the earth, and environmental remediation has become an immediate priority. Among various environmental remediation techniques, piezocatalytic techniques, which uniquely take advantage of the piezoelectric effect, have attracted much attention. Piezoelectric effects allow pollutant degradation directly, while also enhancing photocatalysis by reducing the recombination of photogenerated carriers. In this Review, we provide a comprehensive summary of recent developments in piezocatalytic techniques for environmental remediation. The origin of the piezoelectric effect as well as classification of piezoelectric materials and their application in environmental remediation are systematically summarized. We also analyze the potential underlying mechanisms. Finally, urgent problems and the future development of piezocatalytic techniques are discussed. [ABSTRACT FROM AUTHOR]

The rapid development of advanced manufacturing technologies in micro-electro-mechanical system (MEMS) fields has promoted the advance in wearable electronics. Among them, wearable biomechanical micro-energy harvesters have attracted much attention in recent years to meet the unique power supply demands of wearable electronics serving as sustainable power sources. In the meanwhile, they also have been successfully demonstrated to be either self-powered sensors or other functional devices for wearable electronic applications. Herein, we overview the state-of-the-art of biomechanical micro-energy harvesters for wearable electronic applications, including the summary of working principles and structural configurations of biomechanical micro-energy harvesters. In detail, three promising technologies for biomechanical micro-energy harvesting are studied, i.e. electromagnetic effect, piezoelectric effect, and electrostatic effect. As for the structural configurations, two essential factors to affect the properties of biomechanical micro-energy harvesters are emphasized, i.e. new materials, and advanced manufacturing technologies. For wearable application scenarios, fiber/fabric-based materials and biodegradable/ecofriendly materials are investigated. For advanced manufacturing technologies, micro/nano fabrication technologies for precise fabrication and large-scale fabrication technologies for mass fabrication are summarized. Moreover, we review the wearable electronic applications of biomechanical micro-energy harvesters for powering, sensing, and actuating, respectively, which reveals the feasibility of constructing the smart wearable microsystems based on the abundant function of biomechanical micro-energy harvesters. Finally, we conclude the review and discussed the future development trends of biomechanical micro-energy harvesters for wearable electronic applications. [ABSTRACT FROM AUTHOR]

Coalesce of photovoltaic effect with converse piezoelectric effect will turn into a photostrictive phenomenon. The current study conceptualizes a 1-3 photostrictive composite consists of a photovoltaic polymer as matrix and fibers of piezoelectric material. The proposed artificial photostrictive composite is capable of replacing lead-based naturally occurring photostrictive material, not only opening a potential for new applications but also caters to tailor the desired properties. Present study employs poly{4,8-bis[5-(2-ethyl-hexyl)thiophen-2-yl]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethylhexyl) carbonyl] thieno[3,4-b] thiophene-4,6-diyl} (PTB7-Th) as organic photovoltaic polymer and Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-35PT) as the fibers. A representative volume element technique (RVE) is employed to embrace the local variation of multi-physics properties. The actuation response of cantilever and simply supported beam bonded to photostrictive composite patch is accurately predicted by finite element method, while discretizing the structure with degenerated shell element. Photostrictive composite with 60% volume fraction of fibers, arranged in square pattern have deflected the cantilever tip to 1.95 mm. Therefore, we provide 1-3 photostrictive composite as a solution for future wireless and lightweight vibration control applications. [ABSTRACT FROM AUTHOR]

Porous (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 (BCZT) piezoelectric ceramics with an oriented directional hole structure were prepared by using the tertbutyl alcohol (TBA)-based freeze-casting method. The influences of sintering temperatures on the microstructure and piezoelectric properties of porous BCZT ceramics were investigated both perpendicular and parallel to the freezing direction. With the increase in sintering temperatures and the porosities decreased from 58% to 42%, the compressive strength increased from 14.0 MPa to 25.0 MPa. In addition, the d33 value of 407 pC/N for the sample sintered at 1400 °C was obtained parallel to the freezing direction, which was 1.40 times that of the other direction. [ABSTRACT FROM AUTHOR]

For photoelectrochemical (PEC) water splitting, the utilization of semiconductor heterojunctions as building blocks for photoanodes allows for high light absorption, effective charge separation, and superior redox capability, greatly boosting the solar energy conversion efficiency. This review mainly focuses on the construction of heterojunction photoanodes, improvement strategies of carrier transmission, and their application in PEC water splitting. First, a series of carrier dynamics characterization methods are introduced to reveal the principle and significance of promoting carrier transport in heterojunctions. Then, from the perspective of the mechanism of promoting the separation and transport of charge carriers, several strategies are summarized and analyzed, including the micro/nanostructure, energy band structure, photothermal effect, piezoelectric effect, pyroelectric effect, ferroelectric effect, and intermediate layer. Finally, the challenges and opportunities for heterojunction photoanodes in PEC reactions are explained clearly, which points the way forward for the development of heterojunctions. [ABSTRACT FROM AUTHOR]

This article provides a comprehensive overview of piezo‐ and ferro‐electric materials based on organic molecules and organic–inorganic hybrids for mechanical energy harvesting. Molecular (organic and organic–inorganic hybrid) piezo‐ and ferroelectric materials exhibit significant advantages over traditional materials due to their simple solution‐phase synthesis, light‐weight nature, thermal stability, mechanical flexibility, high Curie temperature, and attractive piezo‐ and ferroelectric properties. However, the design and understanding of piezo‐ and ferroelectricity in organic and organic–inorganic hybrid materials for piezoelectric energy harvesting applications is less well developed. This review describes the fundamental characterization of piezo‐ and ferroelectricity for a range of recently reported organic and organic–inorganic hybrid materials. The limits of traditional piezoelectric harvesting materials are outlined, followed by an overview of the piezo‐ and ferroelectric properties of organic and organic–inorganic hybrid materials, and their composites, for mechanical energy harvesting. An extensive description of peptide‐based and other biomolecular piezo‐ and ferroelectric materials as a biofriendly alternative to current materials is also provided. Finally, current limitations and future perspectives in this emerging area of research are highlighted. This perspective aims to guide chemists, materials scientists, and engineers in the design of practically useful organic and organic–inorganic hybrid piezo‐ and ferroelectric materials and composites for mechanical energy harvesting. [ABSTRACT FROM AUTHOR]

This article considers pyroelectric energy harvesting using piezoelectric materials such as PZT-5A, PMN-PT, PVDF, and thin-films. A model is developed to predict the power generation based on the temporal change in temperature of the material. The measured and predicted power measurements are compared, where the maximum power density of 0.36 μW/cm² is calculated with PMN-PT. The predicted peak power density under similar boundary conditions for thin-film lead scandium tantalate is over 125 μW/cm². The study concludes that the power density is highly dependent upon the surface area and the pyroelectric coefficient of the material, underlining the importance of maximizing these parameters. [ABSTRACT FROM AUTHOR]

Properties of surfaces often define functionalities and applications of a large variety of materials, e. g. epitaxial growth of thin films, catalytic and optical properties. For this reason, advances in techniques for surface characterization are of great importance. Here we present an overview of the work conducted together with Prof. Meir Lahav over the last decade to detect and quantify near surface polar layers (NSPL). Though thin, these layers may accumulate considerable polarization and, thereby, affect surface properties. We demonstrated that pyroelectric measurement carried out with periodic temperature change protocol (modified Chynoweth) might be a primary tool to study NSPL. Two fundamentally different examples are considered. (i) NSPL in α‐glycine crystals develops as a result of solvent incorporation, e. g. water. This layer is maybe tens or even hundreds of micrometers thick, sometimes, thick enough to allow piezoelectric measurements. (ii) NSPL in SrTiO3 results from surface relaxation and it is only a few Angstroms thick. Nevertheless, NSPL in SrTiO3 has a polarization comparable with strongly ferroelectric materials, tens of μC/cm2. [ABSTRACT FROM AUTHOR]

The size scale effect on the pyroelectric properties is studied for gallium nitride (GaN) nanowires (NWs) based on molecular dynamics simulations and the theoretical analysis. Due to the significant influence of the surface thermoelasticity and piezoelectricity at the nanoscale, the pyroelectric coefficient of GaN NWs is found to depend on the cross-sectional size. This size-dependent pyroelectric coefficient of GaN NWs together with the size-dependent dielectric constant reported in our previous study is employed to study the pyroelectric potential of GaN NWs subjected to heating. The results show that the size scale effect is significant for thin NWs (cross-sectional size in nanometers) and may raise the pyroelectric potential of GaN NWs by over 10 times. Such a size scale effect on the pyroelectric properties of NWs originates from the influence of thermoelasticity, piezoelectricity, and dielectricity at the nanoscale and decreases with increasing cross-section of GaN NWs. It is expected that the present study may have strong implication in the field of energy harvesting at the nanoscale, as pyroelectricity offers a new avenue to the design of novel nanogenerators. [ABSTRACT FROM AUTHOR]

Ferroelectrics form an important class of materials and are employed for a variety of applications. However, specific applications dictate the need of tailored ferroelectric response. This creates a requirement to obtain ferroelectric materials with tunable properties. Generally, chemical modifications or domain engineering are employed to this effect. This study attempts to shed light on the use of compressive pre-stresses for tuning and enhancing the ferroelectric properties. For the purpose, polarization versus electric field hysteresis data for 68Pb(Mn1/3Nb2/3)O3-32PbTiO3 (PMN-PT) single crystals were obtained as a function of uniaxial compressive stresses and operating temperatures. These data were utilized to investigate the effects of mechanical confinement for four individual case studies of electrocaloric effect, electrical energy storage, pyroelectric, and piezoelectric effect. A significant improvement was obtained for all case studies. The adiabatic temperature change was improved by ≈80% (28 MPa, 353 K); energy storage density increased by a factor of five (28 MPa, 353 K); pyroelectric figure of merits improved by an order of magnitude (21 MPa) and the piezoelectric coefficient was tailored (variable stress). The results offer promising insight into the use of directional confinement for improving application specific ferroelectric properties in PMN-PT single crystal. [ABSTRACT FROM AUTHOR]

Spreitzer I et al. i [96] provide a research update on the growth of ferroelectric oxide thin films on silicon, with a particular view toward their applications in piezoelectric micro electromechanical systems (MEMS), electro-optic devices for communications applications, and catalysis and a consideration of the complexities of the silicon-ferroelectric interface. The favored theory for oxide ferroelectrics is the soft-mode theory, and here, we have a perspective by Kamba[79] discussing the results of broadband dielectric, THz, and IR spectroscopic investigations of soft-mode phenomena in H-bonded ferroelectrics, BaTiO SB 3 sb , relaxors, and multiferroics. Domains are also of considerable interest in antiferroelectric materials, and An I et al. i [118] discuss the hierarchical nature of domains in PZT crystals with only 2 at. % Ti, close to the antiferroelectric PbZrO SB 3 sb composition, showing how this forms in the intermediate ferroelectric state and have a significant impact on the materials' physical properties. Subsequently, there has been shown to be a wide range of metal organic complex ferroelectrics, as reviewed by Hang I et al. i [123] In this collection, we have an overview by Yao I et al. i [124] of the potential for bandgap engineering in hybrid organic-inorganic perovskite (HOIP) ferroelectrics such as (MDABCO)(NH SB 4 sb )I SB 3 sb [MDABCO = I N i -methyl I N i '-diazabicyclo(2.2.2)octonium], with the potential for linking the excellent characteristics of the new perovskite materials for solar cells, such as methylammonium lead iodide (MAPbI SB 3 sb ),[125] with the photovoltaic effects seen in ferroelectrics. [Extracted from the article]

Ferroelectric materials have attracted interest for over a hundred years as a result of their spontaneous polarization and a polarization orientation that can be reversed by the application of an external electric field. In addition, the degree of polarization can be affected by external stimuli such as vibrations, stress, heat, and light. These properties enable ferroelectric materials to be used to fabricate nanogenerators, which are devices used in energy scavenging applications and provide an opportunity to obtain electrical energy from a variety of external stimuli. This review discusses the development of ferroelectric‐based nanogenerators for scavenging mechanical, thermal, and solar energies through the piezoelectric effect, pyroelectric effect, and photovoltaic effect, respectively. The mechanisms of the effects and the pathways to optimize the output performance of the nanogenerators are analyzed in detail. Recent developments in energy harvesting using ferroelectric materials are discussed with the objective to motivate attention and efforts in this growing field. [ABSTRACT FROM AUTHOR]

The electroactive β-phase in Poly (vinylidene fluoride, PVDF) is the most desirable conformation due to its highest pyro- and piezoelectric properties, which make it feasible to be used as flexible sensors, wearable electronics, and energy harvesters etc. In this study, we successfully developed a method to obtain high-content β-phase PVDF films and nanofiber meshes by mechanical stretching and electric spinning. The phase transition process and pyro- and piezoelectric effects of stretched films and nanofiber meshes were characterized by monitoring the polarized light microscopy (PLM) images, outputting currents and open-circuit voltages respectively, which were proved to be closely related to stretching ratio (λ) and concentrations. This study could expand a new route for the easy fabrication and wide application of PVDF films or fibers in wearable electronics, sensors, and energy harvesting devices. [ABSTRACT FROM AUTHOR]

Piezoelectric materials have coupled mechanical and electrical energies and have long been used in devices for actuators, sensors, energy harvesters, frequency filters, and various additional applications. Piezoelectricity requires a non‐centrosymmetric crystal structure and is therefore confined to materials that possess a periodic crystalline structure. Due to the non‐crystalline nature of glass, piezoelectricity is fundamentally forbidden. However, one way to exploit piezoelectric properties in a glassy matrix is by developing glass‐ceramics that possess controlled growth of a crystalline phase. Growth and orientation of piezoelectric crystals in a glassy matrix is a non‐trivial process that has long been explored to combine the formability of glass with the thermal and mechanical resilience of glass‐ceramics. While extensive work has been done in the field of functional glass‐ceramics, the results are presented in isolated articles and a comprehensive review pertaining to symmetry breaking methods to exploit anisotropic properties in glass‐ceramics has been absent from the literature. Here, we present a global review of the fundamental symmetry requirements for piezoelectricity, the development of polar, piezoelectric glass‐ceramic compositions (specifically those with LiNbO3 and fresnoite‐based crystal phases), and various crystal growth and orientation mechanisms, including relevant kinetic and thermodynamic driving forces. Lastly, we discuss the challenges associated with implementing gradients to drive oriented crystal growth to develop non‐centrosymmetry, and the need for future modeling work to produce adequate time‐temperature‐transformation (TTT) diagrams that take into account kinetic and thermodynamic driving forces for oriented crystal growth. Going beyond technical challenges, we conclude with an examination of current and potential applications for piezoelectric glass‐ceramics that combine the formability of glass with the symmetry‐dependent properties of ceramics. [ABSTRACT FROM AUTHOR]

Piezoelectric materials have a wide range of industrial applications in different branches of engineering due to their electromechanical coupling. So, investigating their responses to either mechanical or electric loadings helps engineers for efficient design of smart systems. However, most of the studies have assessed the well-known 6 mm piezoelectric materials or piezoceramics and few papers have studied other piezoelectric crystals despite of their application in industry. In this paper, fundamental solutions of a trigonal piezoelectric half-plane belonging to 3m crystal class is obtained. The governing differential equations are derived and solved analytically using potential method. It is shown that the solution for the 3m material can be degenerated to 6 mm solution as a special case. The contour lines were depicted for two practical piezoelectric materials belonging to 3m and 6 mm crystal classes including lithium niobate and PZT-4 and they were compared to each other. The numerical results showed that the response of the trigonal material is asymmetric due to anisotropy and the effect of anisotropy on some responses is considerable causing totally different behavior from 6 mm piezoelectric material. [ABSTRACT FROM AUTHOR]

Waste energy harvesting is a method of generating small amounts of energy, usually through vibrations or thermal energy. Macro-fiber Composites (MFCs) have been employed in energy harvesting applications utilizing the piezoelectric effect, however, energy harvesting using the pyroelectric effect in MFCs has not been thoroughly explored. This paper takes strides in investigating the energy generated using the pyroelectric effect with P1 and P2 MFCs using two different oscillating temperature rates at 5°C/min and 10&#176C/min. Numerical temperature data along with analytical temperature functions were used to model the pyroelectric effect and the result was compared to experimental tests. Depending on the size of the MFC, type, resistor used, and the temperature rate, the energy generated varies from 0.4 to 24 µJ for the P1 MFC, and 8 to 459 µJ for the P2 MFC. The maximum specific power was also estimated analytically, numerically, and experimentally. A resistor sweep was performed using the numerical model to calculate the optimal resistance that would provide the most energy. The resistor was in the Gigaohm (Ω) to Teraohm (Ω) range for the specified temperature profiles. The required resistance to generate the maximum energy decreased as the temperature rate and the size of the MFC increased. This was validated with experiments conducted at varying resistances. Because this is energy generated from the ambient environment, pyroelectric harvesting can be used to power devices without cost to the source. This form of harvesting can be used in any place where there is a natural thermal cycle (i.e. due to weather or machine giving off thermal energy). [ABSTRACT FROM AUTHOR]

This work presents an analytical investigation of a cantilever shape memory alloy (SMA)/piezoelectric laminated composite beam subjected to a tip load with possible temperature variation. The beam consists of two piezoelectric layers of identical thickness bonded to a superelastic SMA core exhibiting asymmetric tensile–compressive behavior. Two loading scenarios are considered where either the temperature of the beam or the applied tip load is varied, while the other parameter is fixed. In each case, the load results in deformation of the SMA core and the piezoelectric layers bonded thereto, leading to the generation of an electric charge. The deformation of the SMA material is modeled based on an extended version of the ZM constitutive relations for SMAs that accounts for intrinsic tensile–compressive asymmetry. Geometric and force equilibrium considerations are used to identify the correct sequence in which different solid-phase structures develop within the superelastic core during a complete loading–unloading process. Temperature-dependent moment and shear force equations are then derived and used in investigating the electrical and mechanical properties of the beam. The proposed model is validated against 3D finite element simulations, and the general trend of output voltage variation with temperature is shown to be consistent with experimental data. [ABSTRACT FROM AUTHOR]

Flexible low-grade waste heat generators are a promising device that can both recycle thermal energy and exhibit elasticity, are light weight, and have easily customized shapes. However, most thermal energy recovery technologies only work at large temperature gradients. Herein, a dynamic generator based on liquid crystal network (LCN) and poly(vinylidenedifluoride--trifluoroethylene) (PVDF-TrFE) is reported. The generator can operate in a temperature of ≈30 °C with a temperature difference of 6 K. LCN expands and shrinks in the temperature fluctuation, which is beneficial for PVDF--TrFE exposure to greater temperature changes. The device is found to exhibit a maximum output voltage of ≈4.5 mV based on pyroelectric and piezoelectric effect. This simple strategy may broaden applications of liquid crystalline actuators for harvesting low-grade waste heat. [ABSTRACT FROM AUTHOR]

Present work is concerned with the analysis of transient wave phenomena in a piezo-thermoelastic medium with diffusion, fiber reinforcement and two-temperature, when an elastic wave is made incident obliquely at the traction free plane boundary of the considered medium. The formulation is applied under the purview of generalized theory of thermoelasticity with one relaxation time. The problem is solved analytically and it is found that there exists four coupled quasi waves: qP (quasi-P), qMD (quasi mass diffusion), qT (quasi thermal) and qSV (quasi-SV) waves propagating with different speeds in a two-dimensional model of the solid. The amplitude ratios, phase velocities and energy ratios for the reflected waves are derived and the numerical computations have been carried out with the help of MATLAB programming. Effect of presence of diffusion is analyzed theoretically, numerically and graphically. The number of reflected waves reduce to three in the absence of diffusion as qMD wave will disappear in that case which is physically admissible. Influence of piezoelectric effect, two temperature and anisotropy is discussed on different characteristics of reflected waves such as phase velocity and reflection coefficients. It has been verified that there is no dissipation of energy at the boundary surface during reflection. Thus, the energy conservation law holds at the surface. Finally, all the reflection coefficients are represented graphically through 3D plots to estimate and highlight the effects of frequency and angle of incidence. [ABSTRACT FROM AUTHOR]