High Piezoelectric Charge Coefficient Research Articles

Remarkable enhancement in piezoelectric performance of [001] textured Na0.4K0.1Bi0.5TiO3 ceramic

This study explores the dependence of dielectric and piezoelectric properties on the grain morphology, orientation, and electric field in the [001] textured Na0.4K0.1Bi0.5TiO3 (NKBT-T) piezoceramics, fabricated via reactive template grain growth and tape-casting methods. A high degree of [001] texturing with Lotgering factor (f) of ∼0.92 was confirmed by X-ray diffraction, electron backscattered diffraction, and bulk texture measurements. A large average plate length of ∼8.5 ± 1 μm with an aspect ratio of ∼11 was achieved in NKBT-T ceramic. An extremely large value of piezoelectric voltage coefficient (g33) of ∼100×10−3 Vm/N was observed in poled NKBT-T ceramics, originating from a low dielectric constant (∼230) and high piezoelectric charge coefficient (d33 ∼205 pC/N). The transduction coefficient (d33•g33) of NKBT-T ceramic was estimated at ∼20,000 × 10−15 m2N−1 and the mechanical energy harvesting responses of ∼1.8 µA and ∼4 V were recorded in the NKBT-T ceramic-based piezoelectric device.

Piezoelectric ceramics with hierarchical macro- and micro-pore channels for sensing applications

Piezoelectric sensors have attracted increasing attention due to their high sensitivity to forces, pressures and acceleration. The use of porous piezoelectric ceramics with aligned pores formed by freeze casting for sensing application also exhibit advantages due to their combination of a high piezoelectric charge coefficient and low permittivity, which leads to an enhancement in sensor sensitivity compared to dense materials. To fabricate porous materials, the process of direct ink writing (DIW) exhibits superiority in terms of structural design as a result of its ability to provide layer-by-layer and mold-free rapid prototyping. This work provides the first demonstration of the fabrication of lead zirconate titanate (PZT) piezoelectric ceramic scaffolds with sophisticated hierarchical porous structures by simultaneous DIW and freeze casting. The morphology of the porous cells and individual layers of the hierarchical porous PZT ceramic scaffolds were designed by adjusting the rheological properties and optimizing the printing path. The effect of cell structure and number of layers on sensing performance was investigated in detail. Manufactured scaffolds with a sandwich structure exhibited a high output voltage (191 V) under the application of 1 N external force, with a sensitivity of 8.98 V·kPa−1. This work provides a new approach to structural design of piezoelectric sensors to inform future efforts in the fabrication of high-performance piezoelectric ceramics with hierarchical porosity with complex and bespoke geometries.

Fine-grained high-performance Ba0.85Ca0.15 Zr0.1Ti0.9O3 piezoceramics obtained by current-controlled flash sintering of nanopowders

Due to environmental concerns, extensive research has been carried out to develop high-performance lead-free piezoceramics capable of replacing commercial lead-based materials. The lead-free (Ba0.7Ca0.3)TiO3 −Ba(Zr0.2Ti0.8)O3 system has emerged as a candidate for room temperature transducer applications because a high piezoelectric charge coefficient is achieved in this system for compositions at the morphotropic phase boundary. However, conventional ceramic processing of these eco-friendly piezoceramics demands high energy consumption because long-lasting, high-temperature heat treatments are needed, which often lead to microstructural degradation that compromises the material reliability. Field-assisted flash sintering has started to be explored since the application of an adequate electric field was shown to significantly reduce the sintering time and temperature, thereby controlling grain growth. In this work, Ba0.85Ca0.15Zr0.1Ti0.9O3 ceramics are obtained by current-controlled flash sintering of mechanosynthesized nanopowders. Exhaustive control of the sintering parameters allows tailoring of the microstructure, which allows dense fine-grained flash-sintered ceramics exhibiting a high electric field-induced strain response to be obtained.

Blue light emitting piezoelectric few-layered borophene nanosheets for flexible nanogenerators

Piezoelectric response from two-dimensional layered materials with semiconducting properties is important for developing nanogenerators, piezotronics, and piezophototronics devices. However, experimental observation of piezoelectricity and semiconductor properties in monoatomic borophene has been a key challenge for the fabrication of nanogenerator devices. Here, we discover the non-centrosymmetric blue light emitting piezoelectric properties of few layered monoatomic borophene nanosheets. We develop the flexible piezoelectric nanogenerator using few layered borophene nanosheets in polydimethylsiloxane polymer, producing an output voltage of 8 V without electrical poling. The material exhibits a high piezoelectric charge coefficient (d33) of 86 pm V−1 and shows band gap opening with a high band gap of 2.32 eV. Surprisingly, the borophene nanosheets exhibit blue light emission under UV light illumination. Under UV light illumination, the device dramatically improves output performance. We find that the material exhibits a high dielectric constant of about 125 at low frequency.

Effect of bicontinuous minimal surface meso-scale geometry on piezoelectric performances of piezoelectric composites

This paper examines the effective piezoelectric properties of ceramic-based composite materials that contain bicontinuous minimal surface structures. Three structures are introduced bicontinuous Schwarz P, bicontinuous Gyroid, and bicontinuous I-WP and the material model is subjected to both compressive and tensile stresses. Using the finite element method, the relationship between the average piezoelectric coefficient and the volume fraction of piezoelectric ceramics is analyzed for different structures. The study reveals that the bicontinuous Gyroid structure exhibits the highest average piezoelectric coefficient of 501 pc/N under a compressive stress of 0.5 Gpa and a piezoelectric ceramic volume fraction of 50%. Additionally, the study compares the three bicontinuous minimal surface structures with 3–3 model piezoelectric composite materials (interconnected random distribution) to explore the piezoelectric ceramic transfer path and the impact of arrangement and combination on piezoelectric properties. The results show that bicontinuous minimal surface piezoelectric composite materials display superior piezoelectric properties, as demonstrated by their high piezoelectric charge coefficient, piezoelectric voltage coefficient, and energy harvesting figure of merit. Overall, this paper provides valuable insights into how the structure of piezoelectric ceramics can be altered to enhance the performance of piezoelectric composite materials.

A high performance lead-free flexible piezoelectric nanogenerator based on AlFeO3 nanorods interspersed in PDMS matrix for biomechanical energy scavenging to sustainably power electronics

Since lead-based piezoelectric nanogenerators (PENGs) possess serious health risks, environmental problems, proper disposal issues, and biocompatibility concerns, this work presents the fabrication of a flexible piezoelectric nanogenerator utilizing lead-free orthorhombic AlFeO3 nanorods for biomechanical energy scavenging to sustainably power electronics. Hydrothermal technique is used to synthesize the AlFeO3 nanorods and the PENG was fabricated on Indium tin oxide (ITO) coated Polyethylene terephthalate (PET) flexible film with AlFeO3 nanorods interspersed in polydimethylsiloxane (PDMS). transmission electron microscopy proved that the AlFeO3 nanoparticles are of nanorods shape. Through x-ray Diffraction, it is validated that AlFeO3 nanorods have orthorhombic phase and crystalline structure. A high piezoelectric charge coefficient (d 33 ) of 400 pm V−1 is obtained from the piezoelectric force microscopy of AlFeO3 nanorods. With optimized concentration of AlFeO3 in the polymer matrix, an open circuit voltage (V OC) of 30.5 V, current density (J C) of 0.7888 μA cm−2 and an instantaneous power density of 240.6 mW m−2 are obtained under the application of a force of 1.25 kgf. To investigate the nanogenerator’s practical utility, the PENG is used for lighting multiple LEDs, charging of a capacitor and as a pedometer via biomechanical energy harvesting. Hence, it can be employed for developing various self-powered wearable electronics such as flexible skin, artificial cutaneous sensors, etc.

Enhanced piezoelectricity in lead-free halide perovskite nanocomposite for self-powered wireless electronics

Lately, lead-free flexible piezoelectric nanogenerators (PENGs) have drawn much attention because of the threat posed by lead (Pb)-based piezoelectric materials to the environment. Here, we reported an organic-inorganic hybrid perovskites (OIHP) PENG, which is a combination of lead-free formamidinium tin (Sn) halide perovskite (CH(NH2)2SnBr3 (FASnBr3)) nanoparticles (NPs) and polydimethylsiloxane (PDMS) polymer matrix. By using piezoelectric force microscopy (PFM) measurements, we unveil the excellent piezoelectric properties of the FASnBr3 NPs with a high piezoelectric charge coefficient (d33) of ~ 50 pm/V. Due to the outstanding flexibility and uniform distribution properties, the device demonstrated a maximum piezoelectric peak to peak output voltage of 94.5 Vp-p, peak to peak current of 19.1 μAp-p, and output power density of 18.95 μW/cm2 with a tiny force of 4.2 N; these characteristics substantially outperform a number of the state-of-the-art halide perovskite based PENGs (Table S1). Given their high electromechanical energy conversion efficiency, the electrical energy produced from the PENGs was used to power a Bluetooth-capable system on chip (SoC) to build an entirely self-powered radio frequency (RF) communication system. For the first time, we established a self-powered RF wireless communication between nanogenerator and smart electronic devices which is solely based on a lead-free PENG. It is anticipated that the fabricated FASnBr3 @PDMS nanocomposite PENG not only possesses outstanding performance and reliability but also serves as a stepping-stone towards achieving self-powered Internet of Things (IoT) devices built using environment-friendly perovskite piezoelectric materials.

Optimizing energy harvesting performance by tailoring ferroelectric/relaxor behavior in KNN-based piezoceramics

Piezoelectric energy harvesters (PEHs) fabricated using piezoceramics could convert directly the mechanical vibration energy in the environment into electrical energy. The high piezoelectric charge coefficient (d33) and large piezoelectric voltage coefficient (g33) are key factors for the high-performance PEHs. However, high d33 and large g33 are difficult to simultaneously achieve with respect to g33 = d33/(ε0εr) and d33 = 2Qε0εrPr. Herein, the energy harvesting performance is optimized by tailoring the CaZrO3 content in (0.964−x)(K0.52Na0.48)(Nb0.96Sb0.04)O3 −0.036(Bi0.5Na0.5)ZrO3−xCaZrO3 ceramics. First, the doping CaZrO3 could enhance the dielectric relaxation due to the compositional fluctuation and structural disordering, and thus reduce the domain size to ∼30 nm for x = 0.006 sample. The nanodomains switch easily to external electric field, resulting in large polarization. Second, the rhombohedral–orthorhombic–tetragonal phases coexist in x = 0.006 sample, which reduces the polarization anisotropy and thus improves the piezoelectric properties. The multiphase coexistence structures and miniaturized domains contribute to the excellent piezoelectric properties of d33 (354 pC/N). Furthermore, the dielectric relative permittivity (εr) reduces monotonously as the CaZrO3 content increases due to the relatively low ion polarizability of Ca2+ and Zr4+. As a result, the optimized energy conversion coefficient (d33 × g33, 5508 × 10−15 m2/N) is achieved for x = 0.006 sample. Most importantly, the assembled PEH with the optimal specimen shows the excellent output power (∼48 µW) and lights up 45 red commercial light-emitting diodes (LEDs). This work demonstrates that tailoring ferroelectric/relaxor behavior in (K,Na)NbO3-based piezoelectric ceramics could effectively enhance the electrical output of PEHs.

Single fibre enables acoustic fabrics via nanometre-scale vibrations.

Fabrics, by virtue of their composition and structure, have traditionally been used as acoustic absorbers1,2. Here, inspired by the auditory system3, we introduce a fabric that operates as a sensitive audible microphone while retaining the traditional qualities of fabrics, such as machine washability and draping. The fabric medium is composed of high-Young'smodulus textile yarns in the weft of a cotton warp, converting tenuous 10-7-atmosphere pressure waves at audible frequencies into lower-order mechanical vibration modes. Woven into the fabric is a thermally drawn composite piezoelectric fibre that conforms to the fabric and converts the mechanical vibrations into electrical signals. Key to the fibre sensitivity is an elastomeric cladding that concentrates the mechanical stress in a piezocomposite layerwith a high piezoelectric charge coefficient of approximately 46 picocoulombs per newton, a result of the thermal drawing process. Concurrent measurements of electric output and spatial vibration patterns in response to audible acoustic excitation reveal that fabric vibrational modes with nanometre amplitude displacement are the source of the electrical output of the fibre. With the fibre subsuming less than 0.1% of the fabric by volume, a single fibre draw enables tens of square metres of fabric microphone. Three different applications exemplify the usefulness of this study: a woven shirt with dual acoustic fibres measures the precise direction of an acoustic impulse, bidirectional communications are established between two fabrics working as sound emitters and receivers, and a shirt auscultates cardiac sound signals.

Poly(vinylidene fluoride)-Stabilized Black γ-Phase CsPbI3 Perovskite for High-Performance Piezoelectric Nanogenerators.

Halide perovskite materials have been recently recognized as promising materials for piezoelectric nanogenerators (PENGs) due to their potentially strong ferroelectricity and piezoelectricity. Here, we report a new method using a poly(vinylidene fluoride) (PVDF) polymer to achieve excellent long-term stable black γ-phase CsPbI3 and explore the piezoelectric performance on a CsPbI3@PVDF composite film. The PVDF-stabilized black-phase CsPbI3 perovskite composite film can be stable under ambient conditions for more than 60 days and over 24 h while heated at 80 °C. Piezoresponse force spectroscopy measurements revealed that the black CsPbI3/PVDF composite contains well-developed ferroelectric properties with a high piezoelectric charge coefficient (d33) of 28.4 pm/V. The black phase of the CsPbI3-based PVDF composite exhibited 2 times higher performance than the yellow phase of the CsPbI3-based composite. A layer-by-layer stacking method was adopted to tune the thickness of the composite film. A five-layer black-phase CsPbI3@PVDF composite PENG exhibited a voltage output of 26 V and a current density of 1.1 μA/cm2. The output power can reach a peak value of 25 μW. Moreover, the PENG can be utilized to charge capacitors through a bridge rectifier and display good durability without degradation for over 14 000 cyclic tests. These results reveal the feasibility of the all-inorganic perovskite for the design and development of high-performance piezoelectric nanogenerators.

Flexible Interconnected Cu‐Ni Nanoalloys Decorated Carbon Nanotube‐Poly(vinylidene fluoride) Piezoelectric Nanogenerator

AbstractHerein, high‐performance flexible and stable Cu‐Ni nanoalloy decorated carbon nanotube (CNT) reinforced poly(vinylidene fluoride) (PVDF) based piezoelectric nanogenerator is presented for the first time with very high current and power density. The formation of crystalline β‐phase is confirmed using FT‐IR and Raman spectra analysis. HR‐TEM study reveals the formation of Cu‐Ni nanoalloys with well‐defined interconnected structure with CNT. The Cu‐Ni nanoalloy decorated CNT‐PVDF nanogenerator device exhibits a high output voltage of 12 V and high current density of 0.3 µA cm−2 compared to pristine PVDF nanogenerator (4 V and 10 nA cm−2). Very high power density of 204 µW cm−3 is obtained from the nanocomposite nanogenerator. Piezoelectric force microscopy study reveals very high piezoelectric charge coefficient (d33) of about 160 pm V−1 from Cu‐Ni decorated CNT‐PVDF. Very stable output performance with almost no degradation till 1500 cycles is observed from the Cu‐Ni nanoalloy CNT‐PVDF nanogenerator. Such high stability is due to its dramatic improved high tensile strength of 60 MPa. Very high dielectric constant of 500 is observed from Cu‐Ni decorated CNT‐PVDF as compared to pristine PVDF (ε’ ≈ 20). The dramatic increase in output performance even under without electrical poling is discussed in light of self‐dipole alignment, in‐situ poling, high d33, interfacial polarization, and enhanced dielectric properties.

Piezoelectric Properties of (1 – X)BiScO3 – XPbTiO3 System for Actuator Applications

ABSTRACTIn this research, the crystalline and piezoelectric properties of (1 – X )BiScO3–XPbTiO3 (X = 0.60, 0.62, 0.64, 0.66 and 0.68) ceramics were investigated to determine the optimized composition for energy harvester and sensor applications. BS-PT ceramics have strong merits in terms of their high Curie temperature and piezoelectric charge coefficient. Devices of the (1 – X )BS-XPT ceramics were fabricated by a conventional mixed-oxide sintering process with nano-powders. By employing the X-ray diffraction patterns, the morphotropic phase boundary (MPB) region of the monoclinic and tetragonal phases was identified at X = 0.64. Near the MPB region, the piezoelectric and dielectric properties of BS-PT ceramics were improved compared with those of other composition. By optimizing the compositions of the BS-PT ceramics, the maximum values of the dielectric constant (εr), piezoelectric charge coefficient (d33), electromechanical coupling factor (kp) and remanent polarization (Pr) were obtained, with values of 1387, 417 pC/N, 51.4% and 44.8 µC/cm2, respectively. Moreover, a high Curie temperature of 399.2 °C and inverse piezoelectric charge coefficient of 574 pm/V were observed for the 0.36BS–0.64PT composition, which can be a huge merit for actuator applications. These high piezoelectric charge coefficients and inverse piezoelectric charge coefficients can be the strong merits for energy harvester and actuator applications.

A Systematic Review of Piezoelectric Materials and Energy Harvesters for Industrial Applications.

In the last three decades, smart materials have become popular. The piezoelectric materials have shown key characteristics for engineering applications, such as in sensors and actuators for industrial use. Because of their excellent mechanical-to-electrical and vice versa energy conversion properties, piezoelectric materials with high piezoelectric charge and voltage coefficient have been tested in renewable energy applications. The fundamental component of the energy harvester is the piezoelectric material, which, when subjected to mechanical vibrations or applied stress, induces the displaced ions in the material and results in a net electric charge due to the dipole moment of the unit cell. This phenomenon builds an electric potential across the material. In this review article, a detailed study focused on the piezoelectric energy harvesters (PEH’s) is reported. In addition, the fundamental idea about piezoelectric materials, along with their modeling for various applications, are detailed systematically. Then a summary of previous studies based on PEH’s other applications is listed, considering the technical aspects and methodologies. A discussion has been provided as a critical review of current challenges in this field. As a result, this review can provide a guideline for the scholars who want to use PEH’s for their research.

Multiscale Heterogeneity Strategy in Piezoceramics for Enhanced Energy Harvesting Performances.

Piezoelectric energy harvesters (PEHs) with piezoceramics as the core can convert low-frequency vibration energy that is ubiquitous in the environment into electrical energy and are at the frontier of research in the field of energy. The high piezoelectric charge coefficient (d) together with the large piezoelectric voltage coefficient (g) are essential for enhancing the energy harvesting performances of PEHs working on a nonresonant state. However, conventional doping and solid solution design strategies lead to the same increase or decrease trend of d and dielectric permittivity ε, making it difficult to obtain a high g value because g = d/ε. Herein, exceptionally well-balanced performances of high d and large g are achieved simultaneously in modified Pb(Zr, Ti)O3(PZT)-based ceramics via a multiscale heterogeneity strategy, which involves coordination among the defect dipole, hierarchical domain, and composite. The electromechanical parameters of the optimal specimen are not only superior to those of many state-of-the-art commercial counterparts but also exhibit good thermal stability. Most importantly, the assembled PEH with the optimal specimen shows excellent variable temperature power generation characteristics. This work provides a paradigm for building PEH material through a multiscale heterogeneity strategy, expected to benefit a wide range of electromechanical coupling materials.

Fabrication and characterization of PU/NKLNT/CFs based lead-free piezoelectric composite for energy harvesting application

ABSTRACT For vibration energy harvesting applications, a flexible composite material based on a polyurethane (PU) polymer matrix filled with polycrystalline particles (Na0.535K0.48)0.966 Li0.058 Nb0.9Ta0.1O3 (NKLNT) and crushed carbon fibers (CFs) has been developed by tape-casting method. NKLNT was synthesized by the solid-state route. The powder mixture of NKLNT and CFs was dispersed in the solution obtained by dissolving polyurethane in Cyclohexane. A maximum electrical power has been obtained for 0.5 wt.% at an electrical resistance of 5.105 Ω, which allows us to supply low-power electronic systems. A high piezoelectric charge coefficient (d33 = 147pC.N−1) of NKLNT indicates its potential application in flexible energy harvesting.

Improvement of Figure of Merit Pb(Zr,Ti)O₃-Pb(Zn,Ni,Nb)O₃-Pb(In,Nb)O₃ Piezoelectric Ceramics.

Figure of merit the product of piezoelectric charge constant and the piezoelectric voltage constant-d33 × g33 in piezoelectric energy harvesting systems are critical measures in energy harvester applications. It is difficult to achieve high figure of merit because of the interdependence of d33 and the relative dielectric constant, εr. Until now, the prohibitive amount of effort required to solve this problem has led to it being considered an unsolvable issue. Lead zirconate titanate ceramic, Pb(Zr,Ti)O₃, has been reported to exhibit high values of d33 and εr. However, to be employed as piezoelectric energy harvester, a candidate material is required to exhibit both high piezoelectric charge coefficient and high piezoelectric electric voltage coefficient simultaneously. To enhance the figure of merit of Pb(Zr,Ti)O₃-based materials, dopants have also been considered. Pb(Zn,Ni,Nb)O₃- added Pb(Zr,Ti)O₃, Pb(Zr,Ti)O₃-Pb(Zn,Ni,Nb)O₃ ceramic has been reported to exhibit a high d33 value of 561 pC/N. It's dielectric constant has also been reported to be low at 1898. In this study, Pb(Zr,Ti)O₃-Pb(Zn,Ni,Nb)O₃-Pb(In,Nb)O₃ was investigated in the context of enhancing the figure of merit of Pb(Zr,Ti)O₃-based materials. During the proposed process, we increased the corresponding figure of merit by adding Pb(In,Nb)O₃ material. Besides exhibiting a low dielectric constant, the Pb(In,Nb)O₃ material was also observed to exhibit high d33 × g33 as the proposed doping increased the value of d33 greatly, while maintaining the dielectric constant (Yan, J., et al., 2019. Large engancement of trans coefficient in PZT-PZN energy harvesting system through introducing low εrPIN relaxor. Journal of the European Ceramic Society, 39, pp.2666-2672). Further, we conducted an optimization experiment by controlling the doping concentration and the sintering temperature.

Printed Acoustic Sensor for Low Concentration Volatile Organic Compound Monitoring

Printed electronics employing flexible substrate offers prospective features for various applications such as, tactile sensing, energy harvesting, wearable electronics and acoustic wave sensors. In this work, an acoustic FPW (flexural plate wave) sensor is printed on thin and flexible PZT-PDMS (lead zirconate titanate-poly dimethyl siloxane) composite film with silver ink. The prototype FPW resonator has a resonant frequency of 22.65 MHz with an attenuation of -1.552 dBm. Gravimetric mass sensitivity of the sensor was measured by applying PDMS layers in between the input and output interdigital transducers (IDTs). The mass sensitivity was measured to be -7.8 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /g. The sensor is highly responsive to VOCs (volatile organic compounds) with PDMS as a sensing layer. Gas sensitivities with acetic acid and toluene concentrations were measured to be 0.66 and 160.63 kHz/ppm, respectively. The limit of detection for acetic acid and toluene were 10.9 and 0.03 ppm, respectively. Further, the sensor shows good repeatability and response time with both the VOCs. The thermal stability and high piezoelectric charge coefficient of PZT-PDMS composite compared to other piezoelectric composite and polymer substrates are advantageous for the flexible printed sensor. The reported FPW gas sensor shows potential for low concentration measurement of VOCs.

Improved strain and transduction values of low-temperature sintered CuO-doped PZT-PZNN soft piezoelectric materials for energy harvester applications

In this study the low-temperature sintering effects and improved piezoelectric properties of CuO-doped 0.69 Pb(Zr0.47Ti0.53)O3-0.31[Pb(Zn0.4Ni0.6)1/3Nb2/3]O3 ceramics were investigated. At high temperatures, a sintered Pb(Zr,Ti)O3–Pb(Zn,Ni)NbO3 material has excellent piezoelectric properties such as a high piezoelectric charge coefficient (d33), high electromechanical coupling coefficient (kp), and high relative dielectric permittivity (εr). However, low-temperature sintering of functional ceramics is important for industrial device applications. For sensor applications, sintering or fabrication temperature is important because processing temperatures can interfere with process and material compatibility. Therefore, in this study, low-temperature sintering effects were investigated by employing low-temperature sintering aids while maintaining the piezoelectric properties. CuO was selected as the sintering aid for these applications. We will investigate and discuss the effects of the low-temperature sintering aid of CuO on the Pb(Zr,Ti)O3–P(Zn,Ni)NbO3 material in device applications. By employing the CuO dopant to Pb(Zr,Ti)O3–P(Zn,Ni)NbO3 material, the strain and transduction values were increased while reducing the sintering temperature.

Porous sandwich structures based on BaZrTiO3–BaCaTiO3 ceramics for piezoelectric energy harvesting

Abstract In this study, porous sandwich structures based on barium zirconate titanate–barium calcium titanate (BZT–BCT) ceramics are investigated for energy harvesting applications. To improve the piezoelectric energy harvesting performance, porous sandwich structures based on the BZT–BCT ceramics produced by the tape casting method are designed to be optimum materials with high piezoelectric charge coefficient and low dielectric constant. The dense and porous layer are made of BZT–BCT ceramic sheets and a mixture of BZT–BCT ceramic and polyvinylidene fluoride (PVDF), respectively. Here, the PVDF is a sacrificial material that is volatilized in the burnout process, which results in the formation of pores within the microstructure. Depending on the volume fraction of the porous layer, the BZT–BCT ceramics are manufactured in proportions ranging from 0% to 100 vol%. The 20 vol% of the porous layer exhibits the highest figure of merit (FOM) of 4.53 p.m.2/N. When the volume fraction of the porous layer exceeds 20 vol%, the FOM sharply decreases. The stored energy is calculated by measuring the output voltage on the external capacitor (1 μF) through the full-bridge circuit connected to the specimen. The energy density is calculated by dividing the stored energy by the sample area. The sample with a 20 vol% of the porous layer has an energy density of 7.29 μJ/cm2, which is the highest value attained.

Lead-free 0.95(K0.6Na0.4)NbO3-0.05(Bi0.5Na0.5)ZrO3 ceramic for high temperature dielectric, ferroelectric and piezoelectric applications

Environment-friendly 0.95(K0.6Na0.4)NbO3-0.05(Bi0.5Na0.5)ZrO3(KNN-BNZ) ceramic have been prepared via high energy ball-milling followed by sintering. The effect of sintering temperature on the structural and piezoelectric properties has been studied and optimization of sintering temperature was carried out. X-ray diffraction (XRD) reveals the coexistence of tetragonal and rhombohedral phases for all the samples sintered at different temperatures. The ceramic sample sintered at 1150 °C showed high piezoelectric charge coefficient (d33 = 340 pC/N) with uniform and dense grains. Relaxor type ferroelectric behaviour with Curie phase temperature around 347 °C (at 1 kHz) was obtained. Well saturated and fatigue resistant P-E hysteresis loops with a remnant polarization (Pr) of 19.58 μC/cm2 and a coercive field (Ec) of 14.24 kV/cm were obtained at room temperature. A high value of pyroelectric coefficient (p ∼1855.1 μC m−2oC−1) was obtained in the temperature range 90–150 °C suitable for pyroelectric applications. Further, piezoelectric generator was fabricated using KNN-BNZ ceramic. An open circuit voltage of ∼6.2 V was generated from the device under periodic compressive force of 2 kgf. Thus, 0.95(K0.6Na0.4)NbO3-0.05(Bi0.5Na0.5)ZrO3 ceramic can serve as promising material for various electromechanical, ferroelectric and pyroelectric based devices.