High D33 Research Articles

Molybdenum sulphide incorporated flexible poly(vinylidene fluoride) nanocomposites for energy harvesting and water remediation by dye degradation via piezocatalysis

AbstractMolybdenum sulphide (MoS2) was incorporated into poly(vinylidene difluoride) (PVDF) matrix via melt‐mixing followed by solution casting, to prepare PVDF/MoS2 nanocomposite films with varying MoS2 concentration. Piezoelectric properties of PVDF/MoS2 nanocomposites were significantly boosted by incorporation of MoS2 in PVDF by aiding in the formation of polar phase in the PVDF/MoS2 nanocomposites. Formation of electroactive phases in PVDF/MoS2 nanocomposites was analyzed through Fourier transform infrared and Raman spectroscopic analyses, which also highlighted the interactions between MoS2 and PVDF dipoles. A remarkable polar phase content of ~97% was achieved in the PVDF/3 MoS2 nanocomposite (containing 3 wt% MoS2). Dielectric and ferroelectric investigations further supported the enhancement of interfacial polarization in PVDF/MoS2 nanocomposite films. Piezoelectric response of the fabricated devices was subsequently assessed, demonstrating an output voltage of ~96 V generated through human‐hand actuation on the PVDF/3 MoS2 nanocomposite film. Additionally, the fabricated device exhibited a substantial volumetric power density of ~150 μW/cm2 and a current density of ~7.2 μA/cm2. Notably, the optimized PVDF/MoS2 nanocomposite film exhibited significant degradation efficiencies of ~69.7% and ~67.4% in case of Methylene Blue and Rhodamine B dye, respectively. The successful fabrication of a piezocatalytic PVDF/MoS2 nanocomposite film provided valuable insights into the piezoelectric response for the degradation of various dyes.Highlights Self‐polarized PVDF/MoS2 nanocomposite with high polar phase content (∼97%) has been achieved via melt‐mixing followed by solution casting. High d33 value of ~72 pm/V was achieved in the PVDF/3 MoS2 nanocomposite. PVDF/3 MoS2 nanocomposite based piezoelectric nanogenerator can generate an output voltage of ~96 V under 3 N with sensitivity of ~26 V/N. Power density of ~150 μW/cm2 and current density of ~7.2 μA/cm2 were obtained. PVDF/3 MoS2 nanocomposite film acted as an effective piezocatalysts for the degradation of organic dye with >69% efficiency.

Novel high-TC piezo-/ferroelectric ceramics based on a medium-entropy morphotropic phase boundary design strategy

The medium- or high-entropy strategy has emerged as a new paradigm for designing high-performance piezoelectric ceramics. However, the effectiveness of this approach remains unclear to the development of high Curie temperature (TC) piezo-/ferroelectric materials with outstanding performance. To develop high-performance piezo-/ferroelectric materials suitable for high-temperature environments, in this work, we design a novel ceramic system based on a medium-entropy morphotropic phase boundary (ME-MPB) strategy. Piezo-/ferroelectric ceramics of the formula, Pb(Yb1/2Nb1/2)O3–Pb(In1/2Nb1/2)O3–PbTiO3, meeting the medium entropy criteria, were successfully synthesized using the conventional solid-state reaction method. The crystal structure, microstructure, dielectric, piezoelectric, and ferroelectric properties of the ceramics of the ME-MPB compositions were systematically investigated. X-ray diffraction and scanning electron microscopy analyses revealed that these ceramics possess a pure perovskite phase and dense microstructure. Notably, the prepared ceramics exhibited exceptional piezoelectric performance, with a high d33 up to 603 pC/N, a large strain of 0.20%, a high remanent polarization of 44.0 μC/cm2, and a high Curie temperature of 362 °C. This study demonstrates an effective design approach based on the ME-MPB strategy and points out a new pathway for developing high-performance materials for high-temperature applications as sensors, thereby expanding the research perspective on the design of medium-entropy piezo-/ferroelectric ceramics.

Tunable Piezoelectric PLLA Nanofiber Membranes for Enhanced Mandibular Repair with Optimal Self-powering Stimulation

Abstract Poly (l-lactic acid) (PLLA) is a biocompatible, biodegradable material with piezoelectric properties, making it a promising candidate for providing self-powered stimulation to accelerate tissue repair. Repairs to various tissues, such as bone, cartilage, and nerve, necessitate distinct piezoelectric characteristics even from the same material. However, the extensive utilization of PLLA piezoelectric scaffolds in various tissue is hindered by their low and single piezoelectric constants. In this study, PLLA nanofiber membranes with enhanced and adjustable piezoelectric constants (d33) were fabricated through oriented electrospinning. By carefully controlling the parameters of the spinning solution, a steady increase in d33 values from 0 to 30 pC/N was achieved. This advancement allows tailoring of PLLA nanofiber membranes to meet various piezoelectric requirements of different tissues. As an example of tailoring the optimal piezoelectric constants, we developed PLLA-2-0, PLLA-2-10, PLLA-2-15 and PLLA-2-20 nanofiber membranes with d33 values of 0, 5, 10 and 15 pC/N, respectively. The impact of varying piezoelectric constants of PLLA nanofiber membranes on cellular behavior and repair efficacy were validated through in vitro cellular experiments and in vivo mandibular critical defect repair. The results indicated that PLLA-2-20 demonstrated superior cell proliferation rate up to 130% and an osteogenic differentiation level approximately twice of the control. In addition, PLLA-2-20 significantly promoted cell adhesion and migration, and the cell aspect ratio was about 5 times higher than that of the control group. In vivo, PLLA-2-20 optimal restorative effects on rat mandibles via endogenous mechanical force-mediated piezoelectric stimulation, leading to complete histological restoration within 8 weeks. These findings highlight the potential of the PLLA membranes with high and adjustable d33 by a straightforward process. This study provides a novel approach for the development of highly electroactive membranes tailored to specific tissue repair needs.

Simultaneously Achieved High Piezoelectricity and High Resistivity in Na0.5Bi4.5Ti4O15-Based Ceramics with High Curie Temperature.

Good piezoelectricity and high resistivity are prerequisites for high-temperature acceleration sensors to function correctly in high-temperature environments. Bismuth layered structure ferroelectrics (BLSFs) are promising candidates for piezoelectric ceramics with excellent piezoelectric performance at high temperatures, high electrical resistivity, and high Curie temperatures (Tc). In this study, (LiMn)5+ is substituted for Bi at the A-site, and Ce-doping is performed to replace Ti ions in Na0.5Bi4.5Ti4O15, which achieves the desired combination of high piezoelectric coefficients and high resistivity. Herein, we prepared Na0.5Bi3(LiMn)0.9Ti4-xCexO15 high-temperature piezoelectric ceramics, achieving a high piezoelectric coefficient d33 of 32.0 pC/N and a high resistivity ρ of 1.2 × 108 Ω·cm (at 500 °C), and a high Curie temperature of 648 °C. It is important that the d33 variation remains within 8% over a wide temperature range from 25 °C to 600 °C, demonstrating excellent thermal stability. Structural characterization and microstructure analysis showed that the excellent piezoelectric coefficient and high resistivity of cerium-doped Na0.5Bi4.5Ti4O15-based ceramics are attributable to the synergistic effects of structural characteristics, defect concentration, refined grain size and domain morphology. This study demonstrates that the superior properties of Na0.5Bi3(LiMn)0.9Ti4-xCexO15 ceramics are crucial for the stable operation of high-temperature accelerometer sensors and for the development of high-temperature devices.

Enhanced piezoelectric response of Na0.5Bi0.5TiO3-BaTiO3 lead free ceramics by tuning the local polar heterogeneity

For (1-x)Na0.5Bi0.5TiO3-xBaTiO3 (NBT-BT) ceramics, the highest piezoelectric performances appears at morphotropic phase boundary (x=0.06∼0.10). Recently, quenching has been as an effective way to improve their piezoelectric performances. In this work, comparative study on normally cooled and quenched NBT-BT ceramics was conducted. We found, there is a close positive correlation between electrical properties and local polar heterogeneity. It was verified in a case study on NBBT6 ceramics by tuning the local polar heterogeneity using Bi or Sr nonstoichiometric modification. And the highest d33 ∼ 207 pC/N is obtained in Bi-modified NBT-BT ceramics. It demonstrates that, to obtain a higher d33, the factors affecting local polar heterogeneity of piezoelectric ceramics could be preferentially considered.

Enhancement of piezoelectric properties and temperature stability of high-Curie temperature CaBi2Nb2O9 ceramics

Next-generation jet engines, metal forging processes, and non-destructive monitoring of nuclear power plants demand piezoelectric sensors with ultra-high operating temperature, exceptional sensitivity, and outstanding temperature stability. Bismuth calcium niobate (CaBi2Nb2O9, CBNO) is considered a candidate for high-temperature piezoelectric materials due to high-Curie temperature (TC) near 900 °C. However, pure CBNO shows a poor piezoelectric coefficient (d33) and low high-temperature resistivity (ρ). In this work, the piezoelectricity, ferroelectricity, and resistivity of CBNO ceramics were significantly improved by constructing pseudo-tetragonal boundary through the co-substitution of Li/Ce at A site and W/Mo at B site. Remarkably, Ca0.92(Li0.5Ce0.5)0.08Bi2Nb1.97(W2/3Mo1/3)0.03O9 (CLCBN-3WM) ceramic exhibits the best performance: ultra-high TC (∼ 922 °C), very high d33 (∼ 16.1 pC/N), a large remanent polarization (∼ 11.61 μC/cm2), and very good high-temperature insulation ρ (∼ 7.4 × 105 Ω·cm at 600 °C), as well as excellent thermal stability with its d33 value degeneration from 16.1 pC/N to 15.1 pC/N from room temperature to 800 °C (less than 7.0 %). These results indicate that CLCBN-3WM ceramics have significant potential for using in electromechanical transducers operating at high temperatures (600 °C or higher).

High mechanical quality factor and high piezoelectric coefficient achieved via acceptor-modified invisible boundary

High mechanical quality factor (Qm) and high piezoelectric coefficient (d33) are desired for high-power applications of piezoelectric ceramics. However, achieving them based on currently known mechanisms has proven challenging because of the tradeoff between Qm and d33. Here we report a surprising finding that this tradeoff can be overcome via acceptor-modified invisible-boundary (IB). High Qm ∼1096 and high d33 ∼337 pC/N were achieved and superior to those of both lead-free and commercial lead-based piezoceramics. The acceptor-modified IB was demonstrated in Fe-doped BaTi0.89Hf0.11O3 ceramics, where the acceptor doping in the IB composition increases Qm by ∼8.6 times and d33 by ∼1.5 times, being different from the acceptor doping effect in morphotropic/polymorphic phase boundary (MPB/PPB) compositions of increasing Qm but decreasing d33. We predict that our finding may also be made in other acceptor-modified IB systems and the obtained high-performance BaTiO3-based piezoceramic could provide an alternative to lead-based piezoceramics in underwater applications.

A-site and B-site cation doping engineering: A strategy to enhance strain in Pb(Zr, Ti)O3-based ceramics

Pb(Zr, Ti)O3 piezoelectric ceramics with high strain and low hysteresis are essential for ultra-precision driving and positioning in advanced manufacturing and control fields. In this study, the doping engineering via dual cations was utilized to improve the strain characteristics of Pb(Zr, Ti)O3-based ceramics, and thus the ceramics 0.3PbTiO3–0.65PbZrO3–0.05(Bi0.3La0.7)(Zn0.5Ti0.5)O3–x wt% (La2O3+Nb2O5) were probed. Results show that excellent comprehensive performance is fulfilled for the ceramic with x = 5, i.e., a high strain S = 0.45 %, low strain hysteresis Hy =16 %, and high piezoelectric coefficient d33 = 585 pC/N. For modified ceramics, the large electrostrictive strain stems from the synergistic role of lattice distortion and transformation of electric domain morphology due to cations doping. This study demonstrates a productive cation co-doping engineering to enhance the electrostrictive strain in Pb(Zr, Ti)O3-based ceramics, which enables the ceramics to have good features applied in piezoelectric actuators.

Improved piezoelectric properties and thermal stability in ZnO-modified 0.39BiScO3-0.61PbTiO3 ceramics by structure regulation

In this work, ZnO was introduced into 0.39BiScO3-0.61PbTiO3 (xZn-BS-61PT), and the phase structure and local structure of ceramics were controlled by a combination of cation substitution and ceramic/semiconductor composite, so as to improve the piezoelectric properties and temperature stability of ceramics. Zn2+ substitute B-site Ti4+ of BS-61PT, resulting in a stable coexistence of rhombohedral (R)-tetragonal (T)-monoclinic (M) phases dominated by T phase. Excessive Zn ions displace the Sc ions, making Sc ions spontaneously crystallize at grain boundaries in the form of an oxide at x ≥ 0.015. The piezoelectric coefficient and Curie temperature (d33, Tc) are increased from (326 pC/N, 416 °C) for x = 0 to (431 pC/N, 433 °C) for x= 0.015. After annealing at 200 °C, the ZnO-modified samples still retrain high d33 value (d33 > 330 pC/N). For x=0.015 sample, after aged 12 months, the retrained d33 is 395 pC/N, only down 8%. The improved properties are attributed to the synergistic effects of phase structure, point defects and local electric fields. Our results provide a design strategy to simultaneously improve the piezoelectric properties and temperature stability. Meanwhile, it is beneficial to broaden the phase.boundary (MPB) composition range of BS-xPT ceramics, and reduce the dependence of performance on components.

Superior Piezoelectric Performance in Textured CaBi2Nb2O9 Ferroelectric Ceramics through Rare-Earth Gadolinium Doping and Spark Plasma Sintering.

High-performance piezoelectric ceramics with excellent thermal stability are crucial for high-temperature piezoelectric sensor applications. However, conventional fabrication processes offer limited enhancements in piezoelectric performance. In this study, we achieved a significant breakthrough in the piezoelectric performance of highly textured CaBi2Nb2O9 (CBN) ceramics by incorporating rare-earth gadolinium doping and utilizing spark plasma sintering. The resulting Ca0.97Gd0.03Bi2Nb2O9 (CBN-3Gd) ceramics exhibited superior piezoelectric properties, with a high piezoelectric constant d33 of 26 pC/N and a high Curie temperature TC of 946 °C. We employed piezoresponse force microscopy (PFM) to observe the morphology and dimensions of the ferroelectric domains, revealing a rod-shaped 3D domain configuration. This configuration facilitated polarization rotation in the textured ceramics, as analyzed using X-ray photoelectron spectroscopy (XPS) and polarization-electric field (P-E) hysteresis loops. Furthermore, the textured CBN-3Gd ceramics demonstrated exceptional thermal stability and reliability. The piezoelectric constant d33 decreased by only 11.8% over a temperature range of room temperature to 500 °C, and the DC electrical resistivity remained at 6.7 × 105 Ω cm at 600 °C. This work not only highlights the great potential of textured CBN-based ceramics for high-temperature piezoelectric sensors but also provides a viable strategy for enhancing the performance of piezoelectric materials with large aspect ratio micromorphology.

Multi-iteration active learning for the composition design of potassium–sodium niobate ceramics with enhanced piezoelectric coefficient

The piezoelectricity of piezoceramics considerably depends on the doped compositions. However, the conventional trial-and-error approach to composition design is time-consuming and inefficient when searching for high-performance piezoceramics with various dopants. In this study, we introduce a data-driven framework to accelerate the design and discovery of lead-free (K,Na)NbO3 (KNN) materials with enhanced piezoelectric performance. The proposed framework integrates machine learning with feature engineering, surrogate-based optimisation, and experimentation in an active learning loop. Using feature engineering techniques, we demonstrated that the piezoelectric coefficient d33 of KNN materials can be predicted based on a set of elemental and atomic properties. We evaluated six machine learning models and found that support vector regression with a radial basis function kernel achieved high accuracy in predicting the d33 values of KNN ceramics. After three iterations of experimentation and optimisation, we identified an optimal composition with a relatively high d33 of ∼353 pC/N from thousands of possible compositions using a pure exploitation strategy. This study demonstrates an efficient and systematic approach to the composition design of KNN-based piezoceramics, which can be applied to investigate the diverse functional properties of other materials.

Tailoring the Microstructure and Porosity of Porous Piezoelectric Ceramics for Ultrasonic Transducer Application.

Porous piezoelectric ceramics and composites are advantageous for ultrasonic transducers due to their capability to decouple longitudinal and transverse modes, their improved voltage sensitivity, and their enhanced acoustic matching. However, the design and fabrication of porous piezoelectric ultrasonic transducers with excellent electromechanical properties are still challenging. In this work, porous lead zirconate titanate (PZT) ceramics with an aligned pore structure were prepared using the freeze-cast technique, and the effect of porous structure and porosity on the electromechanical parameters was investigated. The introduction of an aligned pore structure is beneficial to enhance the electromechanical properties and reduce the acoustic impedance. A high d33 (∼530 pC/N), a higher kt (∼0.676), and a lower acoustic impedance (∼10.4 MRalys) were achieved in the porous PZT ceramic with the porosity of 44 vol %. The effect of porosity and pore structure on the decoupling degree of vibration modes and ferroelectric polarization was considered to correct the homogeneous medium model, which can quantify the relationship between the kt and porosity of the porous structure. A demonstration of a piezoelectric ultrasonic transducer based on freeze-cast porous PZT ceramics was presented, which exhibits a -6 dB bandwidth of 52% and a theoretical axial resolution of 520 μm. This work therefore provides a potential alternative of piezoelectric ultrasonic transducers for nondestructive testing and imaging applications.

Improving piezoelectric performance in PMN-0.26 PT single crystal via low frequency AC poling

In this experiment, the alternating current poling (ACP) was applied to the 0.74 Pb(Mg1/3Nb2/3)O3-0.26PbTiO3 (PMN-0.26 PT) single crystal to explore the impact of low frequency (0.1 Hz) ACP on electrical performance. When the poling condition is loading 5 cycles at 14 kV/cm, high piezoelectric coefficient d33 of 1780 pC/N and giant dielectric constant of 5881 are obtained for the ACP treatment sample, enhanced 42.4 % and 14.3 % by contrast with the conventional direct current poling (DCP), respectively. The values of coercive field, maximum strain, and converse piezoelectric constant d33∗ vary considerably around the ferroelectric phase transition detected by polarization-electric field, as well as bipolar and unipolar electric field-induced strain hysteresis loops. In addition, the domain configuration of the ACP sample presents a more periodic stripe-like structure with narrower width and relatively more uniformity after three months aging as compared with the DCP sample, showing the importance of domain engineering in enhancing electrical performance of ferroelectric single crystals.

Development and Field Test of Integrated Electronics Piezoelectric Accelerometer Based on Lead-Free Piezoelectric Ceramic for Centrifugal Pump Monitoring.

In this study, an Integrated Electronics Piezoelectric (IEPE)-type accelerometer based on an environmentally friendly lead-free piezoceramic was fabricated, and its field applicability was verified using a cooling pump owned by the Korea Atomic Energy Research Institute (KAERI). As an environmentally friendly piezoelectric material, 0.96(K,Na)NbO3-0.03(Bi,Na,K,Li)ZrO3-0.01BiScO3 (0.96KNN-0.03BNKLZ-0.01BS) piezoceramic with an optimized piezoelectric charge constant (d33) was introduced. It was manufactured in a ring shape using a solid-state reaction method for application to a compression mode accelerometer. The fabricated ceramic ring has a high piezoelectric constant d33 of ~373 pC/N and a Curie temperature TC of ~330 °C. It was found that the electrical and physical characteristics of the 0.96KNN-0.03BNKLZ-0.01BS piezoceramic were comparable to those of a Pb(Zr,Ti)O3 (PZT) ring ceramic. As a result of a vibration test of the IEPE accelerometer fabricated using the lead-free piezoelectric ceramic, the resonant frequency fr = 20.0 kHz and voltage sensitivity Sv = 101.1 mV/g were confirmed. The fabricated IEPE accelerometer sensor showed an excellent performance equivalent to or superior to that of a commercial IEPE accelerometer sensor based on PZT for general industrial use. A field test was carried out to verify the applicability of the fabricated sensor in an actual industrial environment. The test was conducted by simultaneously installing the developed sensor and a commercial PZT-based sensor in the ball bearing housing location of a centrifugal pump. The centrifugal pump was operated at 1180 RPM, and the generated vibration signals were collected and analyzed. The test results confirmed that the developed eco-friendly lead-free sensor has comparable vibration measurement capability to that of commercial PZT-based sensors.

Enhancing piezoelectric coefficient and thermal stability in lead-free piezoceramics: insights at the atomic-scale

Given the highly temperature-sensitive nature of the polymorphic phase boundaries, attaining excellent piezoelectric coefficient with superior temperature stability in lead-free piezoceramics via direct compositional design remains a formidable challenge. We demonstrate the synergistic improvement of piezoelectric coefficient and thermal stability in lead-free piezoceramics via atomic-scale local ferroelectric structure design. Via modulation of the local Landau energy barrier at doping sites, we effectively mitigate fluctuations in piezoelectric d33. Our approach achieves an impressive d33 of ~430 pC/N with a minimal temperature fluctuation range (△d33 ~ 7%) across the room temperature to 100 °C in potassium sodium niobate ceramics. Further optimization through annealing extends this temperature up to 150 °C (△d33 ~ 8%) while maintaining a high d33 of ~380 pC/N, rivaling the performance of classic temperature stable lead zirconate titanate. This work establishes a framework for addressing the dilemma between high piezoelectric coefficient and inadequate temperature stability in lead-free piezoceramics.

Exploring the mechanisms of enhanced piezoelectric properties in (K,Na)NbO3 single crystals

(K,Na)NbO3 (KNN)-based piezoelectric materials are candidates for replacing Pb-based materials. However, the piezoelectric properties of existing KNN-based single crystals are still inferior to those of Pb-based relaxor ferroelectric single crystals. Moreover, the piezoelectric response mechanism of KNN-based single crystals remains unclear. In this study, (Li,K,Na)(Nb,Sb,Ta)O3:Mn (KNNLST:Mn) single crystals with an excellent piezoelectric coefficient d33 of approximately 778 pC/N were prepared. Systematically studies of intrinsic and extrinsic piezoelectric responses have revealed that the high d33 of KNNLST:Mn single crystals is related to the shear piezoelectric response of a single-domain state and irreversible domain wall motion of the engineering domains. Furthermore, the effect of the orthorhombic (O)-tetragonal (T) phase boundary on intrinsic and extrinsic piezoelectric response is systematically studied, and the impact mechanism is elucidated. The results indicate that a lower dielectric response and elastic constant limit the intrinsic shear piezoelectric response of KNNLST:Mn single crystals, and approaching the O–T phase boundary can enhance both intrinsic and extrinsic piezoelectric responses. This study improves our understanding of the structure-performance relationship in KNN-based single crystals and offers insights for optimizing piezoelectric properties in KNN-based materials.

Enhancing piezoelectric properties of BiScO3-PbTiO3 ceramics via- incorporation of Bi(Zn1/2Ti1/2)O3 with high spontaneous polarization

High-performance piezoelectric materials are the core elements for the fabrication piezoelectric transducers and actuators. In recent years, there has been an increasing demand for piezoelectric materials with both high operational temperature and large piezoelectricity. However, the conventional approach of soft doping to enhance the piezoelectric response often results in a reduction in Curie temperature. To address this issue, we incorporated Bi(Zn1/2Ti1/2)O3 with a large spontaneous polarization (Ps ∼ 100 µC/cm2) and high Curie temperature (Tc ∼ 1380 °C) into BiScO3-PbTiO3 ceramics to improve the piezoelectric response while maintaining high Tc. The newly developed 0.08Bi(Zn1/2Ti1/2)O3-0.335BiScO3-0.585PbTiO3 ceramic exhibits impressive properties including a high d33 value of 585 pC/N (increased by ∼ 33 % compared to the 0.36BiScO3-0.64PbTiO3 ceramics), an electromechanical coupling coefficient k33 of 0.75, a dielectric constant ε′ of 2380, a relatively high Tc of 421 °C. These remarkable improvements hold great promise for advancing high-temperature piezoelectric devices.

Quantitative piezoelectric measurements of partially released Pb(Zr, Ti)O3 structures

The effective large signal longitudinal piezoelectric coefficient (d33,f∗) of piezoelectric thin films on rigid substrates has been widely investigated. Unclamped piezoelectric thin films are predicted to have a higher d33,f∗ coefficient due to reduced constraints on piezoelectric strain, domain reorientation, and domain wall motion, but quantitative measurements of this coefficient have been limited. This study uses microfabrication techniques along with double-beam laser interferometry (DBLI) to accurately determine the longitudinal piezoelectric coefficient of Pb(Zr,Ti)O3 thin films in partially released piezomicroelectromechanical structures. A two-step backside release process was used: first, deep reactive ion etching to create backside vias and second, wet etching of the ZnO sacrificial layer to release the area beneath the Pb(Zr,Ti)O3 thin films. Post wet etching, optical profilometry showed concavely deformed diaphragms resulting from asymmetrical stress profiles through the diaphragm thickness. DBLI was then used to examine diaphragm deflection under an applied unipolar voltage ranging from 0 to 10 V. Devices with 50% and 75% of the area beneath the top electrode released exhibited large signal d33,f∗ values of 410 ± 6 and 420 ± 8 pm/V, respectively, more than three times higher than the d33,f∗ value of the clamped samples: 126 ± 13 pm/V. The reasons contributing to the large d33,f∗ include (i) the change in stress levels due to the release process, (ii) the elimination of mechanical constraints from substrate clamping, and (iii) enhanced domain reorientation. These findings confirm that substrate declamping significantly boosts the piezoelectric coefficient, bringing d33,f∗ closer to the bulk longitudinal piezoelectric coefficient (d33).

Porous Structure Enhances the Longitudinal Piezoelectric Coefficient and Electromechanical Coupling Coefficient of Lead-Free (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3.

The introduction of porosity into ferroelectric ceramics can decrease the effective permittivity, thereby enhancing the open circuit voltage and electrical energy generated by the direct piezoelectric effect. However, the decrease in the longitudinal piezoelectric coefficient (d33) with increasing porosity levels currently limiting the range of pore fractions that can be employed. By introducing aligned lamellar pores into (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3, this paper demonstrates an unusual 22-41% enhancement in the d33 compared to its dense counterpart. This unique combination of high d33 and a low permittivity leads to a significantly improved voltage coefficient (g33), energy harvesting figure of merit (FoM33) and electromechanical coupling coefficient ( ). The underlying mechanism for the improved properties is demonstrated to be a synergy between the low defect concentration and high internal polarizing field within the porous lamellar structure. This work provides insights into the design of porous ferroelectrics for applications related to sensors, energy harvesters, and actuators.

Sm-doped PZT thin film with high piezoelectric properties by sol-gel method

In this study, Pb(Zr0.54Ti0.46)O3 films were prepared by the sol-gel method with Sm doping concentrations of 0, 0.5, 1, 1.5, 2, and 3 mol. %. Their surface morphology, density, crystal structure, piezoelectric, dielectric, and ferroelectric properties were characterized. The results indicated that, unlike Sm-doped lead zirconate titanate (PZT) ceramics, all Sm-PZT films exhibit a significant increase in the grain size compared to undoped PZT films. Moreover, Sm doping affected their crystal orientation and significantly enhanced their piezoelectric coefficient d33 and remnant polarization (Pr). Notably, the Sm-PZT film with a doping concentration of 1.5 mol. % exhibited optimal (100) orientation, achieving a high piezoelectric coefficient d33 of 279.87 pm/V, 4.55 times that of the non-doped PZT films.