Superior Piezoelectric Properties Research Articles

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.

The impact of chemical inhomogeneity in calcinated powders on grain growth behavior and piezoelectric properties of lead-free KNN-based ceramic

Despite outstanding electromechanical properties are achieved in KNN-based ceramics, unstable reproducibility of piezoelectric properties remains a challenge to industrial production, owing to a lack of in-depth understanding of grain growth behavior and chemical homogenization throughout the overall solid-state synthesis process. Herein, a significant chemical heterogeneity behavior was found in calcined 0.957K0.48Na0.52Nb0.96Sb0.04O3-0.04Bi0.5Na0.5ZrO3-0.003CaZrO3 powders owing to non-uniform diffusion and competitive chemical reaction among multicomponent reactants. The chemical heterogeneity is significantly alleviated by modulating calcination temperatures and ball-milling the calcined powders. Furthermore, it was demonstrated that the heterogeneous calcined powder with different particle size distribution played a significant role in grain growth behavior and chemical homogenization of bulk ceramics. Finally, we obtained uniform grain size distribution and preferable chemical homogeneity in ceramics with the calcination of 900 °C and undergone twice ball milling, which exhibited superior piezoelectric properties (d33 = 368 pC/N, kp = 0.52). This work provides an effective paradigm to ameliorate the inferior reproducibility of KNN-based ceramics by effectively regulating the processing condition during solid-state synthesis.

Deposition of highly crystalline AlScN thin films using synchronized high-power impulse magnetron sputtering: From combinatorial screening to piezoelectric devices

With the integration of 5G in day-to-day devices and the foreseeable 6G revolution, demand for advanced radio frequency (RF) microelectromechanical systems (MEMS) is growing. Aluminum scandium nitride (AlScN) has emerged as the material of choice for many of those applications due to its superior piezoelectric and electromechanical properties compared to aluminum nitride (AlN). However, synthesizing high-quality, textured AlScN thin films is challenging. Alloying of Sc in AlN induces structural frustration leading to strain, defects, disoriented grains, and disrupted crystal symmetry during growth. Higher deposition temperatures, while improving crystalline quality, risk undesirable phase precipitation and limit industrial sustainability. In addition, future MEMS technologies also demand conformal and textured coatings over diverse topographies. Addressing these challenges collectively requires new and innovative synthesis approaches. In this study, we investigate the feasibility of ionized physical vapor deposition to deposit highly oriented AlScN films with minimal defects at lower temperatures. To this end, we employ combinations of different deposition approaches, such as metal-ion synchronized (MIS) high-power impulse magnetron sputtering (HiPIMS). Leveraging the high ionization rates of HiPIMS and optimally timed substrate bias potentials, we selectively bombard the growing film with Al and/or Sc ions to enhance the adatom mobility at low temperatures while simultaneously providing the ability to tune stress and coat complex structures conformally. The nonequilibrium solubility of Sc in wurtzite AlN under different conditions is investigated using a combinatorial deposition approach. Promising candidates with ∼20% Sc composition are isolated and characterized for crystallinity and residual stress. Disoriented grains, a significant issue in growing AlScN films, are observed through atomic force microscopy and found to be completely removed by substrate rotation and application of substrate biasing. The measured piezoelectric response of the films with approximately 20% Sc concentration ranges from 6.3 to 8.8 pm/V, in line with density functional theory predictions and experimentally reported values for films deposited in a production tool with coplanar geometry. At the same time, MIS-HiPIMS-deposited films offer unique properties and flexibility to tune their stress state and structural properties, thus presenting exciting opportunities for the fabrication of advanced RF filters and next-generation MEMS devices. Published by the American Physical Society 2024

High-piezoelectric lead-free BiFeO3–BaTiO3 ceramics with enhanced temperature stability and mechanical properties

BiFeO3–BaTiO3 (BF–BT) ceramics exhibit higher piezoelectric coefficients (d33), Curie temperatures (TC), and temperature stability than other high-temperature lead-free piezoelectric materials. However, despite their crucial role in piezoelectric devices, the mechanical properties of BF–BT ceramics have been underexplored. A thorough evaluation of the mechanical properties of BF–BT is crucial for developing cost-effective and durable lead-free piezoelectric ceramics. Moreover, the specific causes of the high piezoelectric response and excellent temperature stability of BF–BT ceramics remain unclear owing to the instrumental detection threshold, which limits experimental studies to temperatures above 140 °C and below the degradation temperature of d33. To investigate the intrinsic origins of the high piezoelectricity and temperature stability of BF–xBT ceramics and to enhance their mechanical properties, a two-step sintering process is used to fabricate these ceramics (0.25 ≤ x ≤ 0.40). Owing to improvements in grain refinement and reduced Bi3+ volatilization, the BF–0.33BT ceramic exhibits enhanced overall performance, with a modified small punch strength of 155 MPa, Vickers hardness of 5.2 GPa, a d33 of 220 pC/N at room temperature, TC of 466 °C, and d33 values exceeding 400 pC/N at 260 °C. Phase-field simulations, which address the limitations of device detection thresholds, reveal that with increasing temperature, the domain structure relaxes, and polarization intensity decreases. This indicates that changes in the high-temperature piezoelectric properties can be attributed to domain structure relaxation and the increase in dielectric constant. Overall, BF–BT ceramics exhibit superior piezoelectric performance, mechanical properties, and temperature stability, making them highly suitable for use in high-temperature and demanding environments.

Structural origin of spin-splitting anisotropy in janus dichalcogenides monolayers under pressure

Abstract Janus transition-metal dichalcogenides (TMDs) have drawn a great deal of attention because of their mirror plane symmetry breaking that allows the emergence of a built-in out-of-plane dipole which determine superior piezoelectric and spin-related properties. Furthermore, it has been shown in the recent literature that pressure application is capable of modulating spin-related phenomena in this class of materials. Generally, the spin-splitting presence in real systems is explored in terms of point group symmetry reduction using solely group theory arguments. However, we seek to associate the enhancement of spin-splitting in Janus TMDs monolayers by searching the most important local asymmetries responsible for the symmetry lowering that leads the monolayer larger spin-splitting energies. In this sense, we seek to unveil a possible structural descriptor that correlates with subbands splitting magnitude in Janus TMDs. To accomplish this, we performed a detailed first-principles investigation into WSSe Janus monolayers under biaxial in-plane strain to find that pressure induces a symmetry lowering from the C 3v to the C s point group. From these observations, we found that in-plane angle asymmetries between the chalcogens yield a distortion metric that can serve as a descriptor for enhanced spin-splitting in Janus WSSe since it strongly correlates with spin-splitting energies. Hence, our work establishes that, rather than solely global symmetry analysis, specific local distortions provide a key design principle to achieve strong spin-splitting in 2D Janus TMDs.

Enhancing the piezoelectric properties and thermal stability of PMN-PMS-PSZT high-power piezoelectric ceramics through defect engineering

The development of high-power piezoelectric ceramics with superior piezoelectric properties and broad temperature usage ranges is vital for the thriving progress of electromechanical applications. However, achieving high piezoelectricity, high mechanical quality factor, and temperature stability often presents a trade-off. In this study, we present an advanced ceramic material with excellent high-power piezoelectric properties and superior temperature stability. The piezoelectric coefficient d33 reaches 348 pC N−1, the electromechanical coupling factor kp is 54%, the mechanical quality factor Qm is 1501, the dielectric loss tanδ is 0.35%, and the d33 variation is less than 10% within 25–210 °C in 0.05Pb(Mg1/3Nb2/3)O3-0.05Pb(Mn1/3Sb2/3)O3-0.9Pb0.95Sr0.05(Zr0.48Ti0.52)O3 ceramic. The excellent piezoelectricity is attributed to the enhancement of intrinsic ionic displacement and reversible domains wall motion because of symmetry-conforming short-range distribution of oxygen vacancy, while the high Qm is a result of increased domain size and oxygen vacancy. The outstanding temperature stability is related to the stable non-180°domains structure due to the oxygen vacancy pinning effect. These properties hold great potential for advanced applications, particularly for piezoelectric high-power applications requiring constant d33 over a broad temperature range.

Enhanced dielectric, ferroelectric and piezoelectric properties of lead-free (Ba,Ca)(Sn,Ti)O3 ceramics by optimisation of sintering temperature

Lead-zirconate-titanate [Pb(Zr,Ti)O3 PZT] crystals possess superior ferroelectric, dielectric and piezoelectric properties. However, due to the toxicity of lead there is a demand for lead-free alternatives. In the present work, we focus on the production of the lead-free (Ba,Ca)(Sn,Ti)O3 (BCST) ceramics via solid-state synthesis method. BCST ceramics calcined at 1050°C, 1100°C, 1150°C, 1200°C and 1250°C were characterized using XRD analysis which showed that at temperatures above 1150°C the structure was free from impurities. Rietveld refinements confirmed a tetragonal structure with P4mm space group for the material calcined at 1150°C. Scanning electron microscopy image analysis of samples sintered at 1200°C, 1250°C and 1300°C showed an increase in grain size and density with temperature. The material sintered at 1300°C had a higher dielectric constant compared to other ceramics. A larger grain size facilitated high ferroelectric polarisation (3.38 μC/cm2), dielectric constant (6100) and d33 piezoelectric coefficient (236 pC/N) for the ceramics. This study demonstrates the potential for using lead-free BCST ceramics for device applications, such as piezoelectric actuators, transducers and ultrasonic motors.

Significant impact of TiO2 purity on the phase structure and electrical properties of BiFeO3–BaTiO3 lead‐free piezoelectric ceramics

AbstractIn many studies, the properties of BiFeO3–BaTiO3 (BF–BT) ceramics vary greatly using different raw reagents, which makes it challenging to obtain reliable and repeatable properties of BF–BT‐based devices. In this work, 0.7BiFeO3–0.3BaTiO3 (0.7BF–0.3BT) ceramics were fabricated by a conventional solid‐phase synthesis using TiO2 reagents with varied purities of 98%, 99%, 99.9%, and 99.99%, respectively. The phase structure, microstructure, ferroelectric, and piezoelectric properties were comprehensively studied. All compositions of the ceramics exhibit a pseudo‐cubic phase perovskite structure, and the fraction of the rhombohedral phase increases with increasing the TiO2 purity. Additionally, backscattered electron images and energy‐dispersive spectroscopy revealed an obvious core–shell structure within grains. In particular, the 0.7BF–0.3BT ceramics prepared with 98% purity TiO2 exhibited superior ferroelectric and piezoelectric properties, d33 ∼ 220 pC/N and ∼ 230 pm/V. The ceramics prepared with higher purity TiO2 suffered from severe leakage conduction, which can be well addressed by adding excess TiO2. Our work reveals the importance of different grades of purity TiO2 on the electrical properties of BF–BT ceramics.

Fully Transparent Flexible Piezoelectric Sensing Materials Based on Electrospun PVDF and Their Device Applications

AbstractAdvanced transducer materials have become increasingly important with the rapid development of the internet of things and flexible electronics. Herein, fully transparent flexible polyvinylidene fluoride/polydimethylsiloxane (PVDF/PDMS) composite piezoelectric films are fabricated using scrape coating techniques based on electrospun PVDF nanofiber films. Compared to the electrospun PVDF, the PVDF/PDMS not only owns high transparency and a more uniform and stable structure but also has superior piezoelectric properties. Based on the electrospun PVDF and the PVDF/PDMS films, flexible piezoelectric sensors are developed, which can effectively detect weak mechanical signals including finger tapping and bending signals, radial artery pulses, and environmental sound signals. The PVDF/PDMS sensor performs better than the electrospun PVDF sensor and presents great potential for applications in flexible sensors and transducers. Especially, thanks to their high transparency, the PVDF/PDMS composite piezoelectric films lend themselves easily to application fields requiring transparent sensors such as imperceptible sensors and human‐machine interfaces, display devices, electronic skins, intelligent windows, etc.

Exploring the electric and Superior Piezoelectric Properties of Two-Dimensional PH-SiX Materials for High-Performance Silicon-Based Devices

The search for advanced two-dimensional materials with exceptional piezoelectric properties has led to the investigation of PH-SiX (X = Cd, Zn, Bi, Ga, and Al) semiconductors, which is compatible with...

Optimizing piezoelectric properties and temperature stability via Nb2O5 doping in PZT-based ceramics

High-performance piezoelectric ceramics with temperature stability can significantly enhance the functionality of transducers and sensors across a range of piezoelectric device applications. In this study, we investigated ceramics composed of 0.16Pb0.92Ba0.08(Mg0.5W0.5)O3-0.84 Pb(Zr0.43Ti0.57)O3 (PBMW-PZT) with varied Nb2O5 content. Notably, the ceramic doped with 1.0 wt% Nb2O5 exhibited superior piezoelectric properties (d33 ∼ 596 pC/N, kp ∼ 67%, and Tc ∼ 284 °C). Moreover, this ceramic demonstrated a stable performance with variations below 10% in the temperature range from 20 °C to 240 °C, surpassing many commercially available PZT-based ceramics. A combination of XRD, SEM, ferroelectric studies, and other in situ analytical methods indicated that this heightened piezoelectric response arises from a marked increase in reversible domain wall movement. The temperature-responsive Raman spectra suggest that the material's temperature stability primarily stems from its inherent structural integrity. Given these findings, the ceramic material in question emerges as an optimal choice for applications in piezoelectric devices, especially transducers and sensors.

New insights into the effect of glass addition on the piezoelectric and thermal stability properties of (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 Pb-free ceramic by defect engineering of MPB

Lead-free piezoceramics with superior piezoelectric properties don't meet the requirements of practical applications due to their lower phase transition temperature and poor thermal stability. In the present work, we report a new insight into the effect of glass phase on the piezoelectric, Curie temperature and thermal stability of (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 (BCZT) ceramic. Unlike traditional glass materials with more than 80% of B2O3 and SiO2 as glass formers, our approach is to fabricate a glass phase (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3-0.05B2O3 (abbreviate BBCZT) with the same elements and concentrations as the ceramic phase. The ceramics-doped glass samples with the composition [(1-x)BCZT-xBBCZT], where x=(0.0, 0.025, 0.05, 0.075 and 0.1 wt%), were sintered according to the glass phase content. The effect of BBCZT glass composition on the crystal structure, dielectric, ferroelectric and piezoelectric properties of BCZT was investigated in detail. X-ray diffraction revealed that the addition of glass phase causes a defect engineering of the tricritical triple point of BCZT ceramic, where the tetragonal (T) and rhombohedral (R) phases were suppressed by the addition of glass phase and the T-phase has completely vanished at x = 0.05. The maximum value of permittivity (ε = 4102) and converse piezoelectric coefficient (d*33 = 1150 Pm/V) were achieved for the 0.975BCZT-0.025BBCZT sample at ambient temperature. Furthermore, the diffusion coefficient (γ) and Curie temperature (Tc) were observed to increase beyond x = 0.025, indicating enhanced thermal stability of BCZT at high glass content. These results qualify that the addition of (BBCZT) can enhance piezoelectric properties, phase transition temperature and thermal stability of BCZT ceramic which can meet wide requirements of practical applications.

Achieving enhanced ferroelectricity and piezoelectric responses in 〈0 0 1〉-textured KNN-BCZT ceramics with BaTiO3 microplates as template

Potassium sodium niobate (KNN) as a typical lead-free piezoelectric ceramic has higher Curie temperature, but its piezoelectric constant is not high enough at room temperature. The introduction of BCZT with high piezoelectric responses into KNN is an important strategy to improve its piezoelectric properties. Moreover, orientation engineering is also a significant method to enhance piezoelectric responses of KNN-based ceramics. Herein, 〈001〉 crystallographic texture in KNN-BCZT ceramics was realized though templated grain growth method with BaTiO3 microplates as template, and the textured sample exhibited superior ferroelectric and piezoelectric properties (2Pr = 43.5μC/cm2, d33*=137 pm/V, d33 = 190 pC/N, kp = 0.54) and lower phase transition temperatures (TO-T = 170.2 °C, TC = 388.3 °C) than randomly oriented sample. This work provides a good strategy to design KNN-based lead-free ceramics with superior piezoelectric properties by constructing solid solution system and controlling crystallographic orientation.

Dielectric and ferroelectric characterization of niobium doped pzt (52/48) nanoceramics

High performance ferroelectric materials have attracted more attention due to its superior dielectric, piezoelectric, and electrostrictive properties. A sol-gel synthesis technique was used to prepare the perovskite Pb(Nbx(Zr0.52Ti0.48)(1−x))O3 (where x = 0, 0.02) nanoceramics. X-ray powder diffraction studies confirm the successful formation of perovskite (ABO3) structure of the ceramics without presence of pyrochlore (A3B4O13) phase which is unwanted for PZT system. Also, the thermogravimetric studies were conducted to confirm the structure formation at elevated temperature. The relative permittivity increases with doping of niobium and curie temperature decreases for the same. The dielectric study of the undoped PZT at the temperature of 500 °C and Nb doped PZT at the temperature of 350 °C for the same frequency of 100 Hz give relative permittivity, εr ≈ 11000 and εr ≈ 1850 respectively. An Arrhenius plot was used to calculate the activation energy and it was found to be 0.210, and 0.161 eV for the undoped and Nb-doped PZT ceramics respectively. The maximum remnant polarization is 1.21 μC/cm2 for niobium doped PZT and 0.16 μC/cm2 for undoped PZT for the applied voltage of 1500 V. The primary goal of this research is to determine how doping with niobium affects the dielectric and ferroelectric properties of PZT (52/48).

Lead-free Bi2CuO4 interspersed into PDMS matrix-based bifunctional piezoelectric nanogenerator for vibrational energy harvesting and visible light photodetection applications

Lead-free materials with superior piezoelectric properties are gaining much interest due to their high performance and increased long-term sustainability. In this context, bismuth-based ternary oxides exhibit perovskite crystal structures with high piezoelectric coefficients and mechanical damping. Thus, in this work, we report a Bi2CuO4: Polydimethylsiloxane (BCO: PDMS) composite -based photoinduced-piezoelectric nanogenerator for harvesting weak mechanical vibrations which are abundant in the atmosphere. Notably, the BCO nanoparticles exhibit a highly crystalline tetragonal structure with 2D-nanoflake-like morphology providing a high surface area for the PENG applications. Further, the optical studies of BCO illustrate an enhanced absorption in the visible region with a bandgap of 2.5 eV. BCO: PDMS-based PENG displays a maximum open circuit voltage of 50 V and short circuit current of 300 nA upon application of 0.15 kgf vertical compressive force without any electrical poling. The PENG device exhibits an 18 % increment in output voltage upon illumination of visible light of 5 mW/cm2 intensity with superior photodetection properties. The obtained response can be attributed to the synergistic effect, i.e., the generation of exciton pairs upon illumination and separation of charge carriers due to the inbuilt piezoelectric field. Moreover, the PENG exhibits a distinct and accurate response for feeble and subtle frequencies in the range of 3–22 Hz such as atmospheric noise, and gravity hum noise. thus, proving the superior sensitivity. The fabricated PENG device displayed a stable response for 30 min of continuous vibration displaying superior cyclic stability. This work demonstrates a combination of perovskite crystalline material and PDMS leading to the development of high-performance piezoelectric nanogenerators with future scope in frequency detection systems for security and safety applications.

Stretchable polymer composites with ultrahigh piezoelectric performance.

Flexible piezoelectric materials capable of withstanding large deformation play key roles in flexible electronics. Ferroelectric ceramics with a high piezoelectric coefficient are inherently brittle, whereas polar polymers exhibit a low piezoelectric coefficient. Here we report a highly stretchable/compressible piezoelectric composite composed of ferroelectric ceramic skeleton, elastomer matrix and relaxor ferroelectric-based hybrid at the ceramic/matrix interface as dielectric transition layers, exhibiting a giant piezoelectric coefficient of 250 picometers per volt, high electromechanical coupling factor keff of 65%, ultralow acoustic impedance of 3MRyl and high cyclic stability under 50% compression strain. The superior flexibility and piezoelectric properties are attributed to the electric polarization and mechanical load transfer paths formed by the ceramic skeleton, and dielectric mismatch mitigation between ceramic fillers and elastomer matrix by the dielectric transition layer. The synergistic fusion of ultrahigh piezoelectric properties and superior flexibility in these polymer composites is expected to drive emerging applications in flexible smart electronics.

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.

Design and manufacture of lead-free eco-friendly cement-based piezoelectric composites achieving superior piezoelectric properties for concrete structure applications

A complex-ion doping strategy fabricates lead-free BCZT ceramic. The excellent properties (d33 ∼ 577 pC/N, Kt ∼ 52%, TC ∼ 110 °C, d∗33 ∼ 620 pm/V, εr ∼ 1820, tanδ ∼ 0.02) were obtained in BCZT ceramic. The in-situ Raman spectroscopy and PFM were conducted to reveal the mechanisms for the superior properties achieved. BCZT ceramics were manufactured for cement-based piezoelectric composites, including 0–3, 2-2 and 1–3 types. 0–3 type (50% BCZT) showed the properties (d33 ∼ 46 pC/N, εr ∼ 310 and Kt ∼ 18.1%). 2-2 and 1–3 types exhibited good piezoelectric properties (d33 ∼ 285 pC/N, εr ∼ 720 and Kt ∼ 33.4% for 2-2 type; d33 ∼ 238 pC/N, εr ∼ 485 and Kt ∼ 29.5% for 1–3 type). Temperature-dependent electrical properties of BCZT-cement composites were systematically explored. Additionally, BCZT ceramic was designed and fabricated for PCD vibration energy harvesting. The output voltage (∼4.9 V) and output power (∼2.4 mW) were obtained. This work underpins the significance of lead-free BCZT ceramic and cement-based piezoelectric composites, and promotes their applications in smart structures.

Nonlinear Dielectric Response of Relaxor Ferroelectric (1 − x)Pb(Mg1/3Nb2/3)O3 − xPbTiO3 Epitaxial Thin Films

AbstractThin ferroelectric layers are capable of generating large dielectric and electromechanical responses at relatively low voltages, thus can be utilized in various applications including energy storage, energy harvesting, sensors, and actuators. Among ferroelectrics, relaxor ferroelectrics (1 − x)Pb(Mg1/3Nb2/3)O3 − xPbTiO3 are particularly interesting due to their superior dielectric and piezoelectric properties. However, dielectric and piezoelectric responses of the ferroelectric thin films are significantly suppressed relative to their bulk counterparts. The physical mechanism of the properties degradation still remains elusive, which greatly hinders their technological applications. Herein, this work systematically investigates the dielectric nonlinearity and the relationship between composition and intrinsic/extrinsic contributions of high‐quality (1 − x)Pb(Mg1/3Nb2/3)O3 − xPbTiO3 epitaxial thin films (x = 0, 0.1, 0.32) fabricated by pulsed laser deposition. Through the Rayleigh analysis, it is found that the suppression of domain wall motion by substrate clamping is the main cause of thin film performance degradation and is further confirmed by continuous application of background dc bias to extract the dielectric response's intrinsic and extrinsic contributions. This work will pave the way for practical applications of (1 − x)Pb(Mg1/3Nb2/3)O3 − xPbTiO3 thin films in energy storage and electromechanical devices.

Ferroelectric composite-based piezoelectric energy harvester for self-powered detection of obstructive sleep

Lead-free piezoelectric ceramic is a promising material for energy harvesters, as they have superior electromechanical, ferroelectric, and piezoelectric properties. In addition, piezoelectric ceramics can be blended with polymer to achieve high-flexibility polymer-ceramic composites, providing mechanical robustness and stability. In this context, a new lead-free ferroelectric material, having the chemical formula SrTi2O5 (STO), was synthesized using a high-temperature solid-state reaction. Detailed analyses of the structural, morphological, and electrical properties of the synthesized material were performed. STO crystallizes with orthorhombic symmetry and space group of Cmm2. The frequency and temperature-dependent dielectric parameters were evaluated, and impedance spectroscopy shed light on the charge dynamics. The PDMS-STO composites at different mass fraction of the STO were prepared using a solvent casting route, and a corresponding piezoelectric nanogenerator (PENG) was developed. The electrical output of the different PENG by varying massfractions of STO in PDMS and varying force were investigated. The 15% (in mass) PENG device delivered the highest peak-to-peak voltage, current, and power density of 25 V, 92 nA, and 0.64 μW @ 500 MΩ, respectively. The biomechanical energy harvesting using the PENG device by daily human motions, bending of the device, and attaching the device to laboratory equipment was demonstrated. Later the PENG device was attached to the human throat region, and snoring signals were recorded. A classification model was designed employing the convolutional neural network (CNN) model. Efforts have been laid to differentiate between normal and abnormal snores, which could help the patient with screening and early disease detection, contributing to self-powered healthcare applications.