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High leakage current density and relatively low piezoelectric activity have become one of the main obstacles to expanding the practical application of Bi4Ti3O12 (BIT) high-temperature piezoelectric ceramics. Although ion doping can improve electrical resistivity and piezoelectric response, it often lowers the Curie temperature. In this work, by introducing CaBi2Nb2O9 (CBN) with higher Curie temperature to BIT, a composite ceramic (1−x)BIT-xCBN was designed, and the effect of CBN content on the structure and electrical properties of the ceramics was investigated. With the increase in the x value, the intensity of the highest peak (117) gradually decreased until disappearing, while the intensity of peak (115) gradually increased, and the X-ray diffraction (XRD) refinement results showed that some non-stoichiometric compounds, Bi1.74Ti2O6.624 and Ca0.5Bi2.5Ti0.5Nb1.5O9, were produced. The sheet-like grains were effectively suppressed, while the granular grains became prominent with high CBN doping content, which should contribute to improving the electrical resistivity of ceramics. The optimal electrical properties were obtained in 0.8BIT-0.2CBN composite ceramics as follows: the piezoelectric coefficient d33 = 13.8 pC/N, the Curie temperature TC = 765°C, and the electrical resistivity ρdc = 8.52 × 105 Ω·cm (@ 500°C). In addition, the d33 maintained 89.1% of the initial value after annealing at 550°C, showing good thermal stability for high-temperature sensing applications. [ABSTRACT FROM AUTHOR]

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)NbO 3 (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 d 33 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 d 33 values of KNN ceramics. After three iterations of experimentation and optimisation, we identified an optimal composition with a relatively high d 33 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. [ABSTRACT FROM AUTHOR]

In recent years, the single-phase BiFeO 3 -BaTiO 3 multiferroic ceramics have gained attention for their magnetoelectric response above room temperature, but substantial endeavors to improve the property have yielded modest results. An optimized BiFe (1-x) Sc x O 3 -BaTiO 3 composition having magnetoelectric coefficient (α ME) ∼ 567 mV/(cm·Oe)) measured at the resonant frequency (∼95 kHz) is reported in this work. The high α ME is attributed to the combined effect of improved piezoelectric coefficient and enhanced ferromagnetism. Improved piezoelectricity is attributed to enhanced intrinsic response caused by the octahedral distortions, and enhanced ferromagnetism is induced by the destabilized cycloidal spin structure resulting from the octahedral distortions. Besides, the addition of Sc3+ can exhibit increased resistivity and reduced defect dipole effects, which is conducive to improving electric properties. [ABSTRACT FROM AUTHOR]

In this work, 1–3 connectivity barium zirconate titanate ceramic cement-based composites were fabricated using Portland cement and epoxy resin as the matrix. Barium zirconate titanate (BZT) of 40–60 % by volume was used while epoxy was used with cement at 0–7% by volume. Dielectric and piezoelectric properties, and other properties such as acoustic impedance, density and microstructure were investigated. It was found that epoxy resin can be used in combination with BZT to achieve a suitable acoustic impedance value (9–11 × 106 kg/m·s2) matching that of concrete for structural health monitoring application. Thus, when epoxy resin was used at 7 %, BZT volume can be increased to 60 % where the highest d 33 value of 93 pC/N was found and remain within the acoustic matching range. In addition, when epoxy resin was increased, both piezoelectric charge coefficient (d 33) and piezoelectric voltage coefficient (g 33) were also found to increase. This is likely due to the lower porosity thus denser matrix when epoxy resin was used in addition to cement. [ABSTRACT FROM AUTHOR]

The piezoelectric properties of Pb(Zr,Ti)O3 (PZT)‐based piezoceramics can be improved by doping with heterovalent ions at the A/B sites. Nd3+ ions were codoped at the A site and Ta5+ ions were doped into the B site of Pb(Zr0.5Ti0.5)(Mg0.5W0.5)(Ni1/3Nb2/3)O3 (xNd2O3‐PZTMWNN) ceramics sintered at a low temperature of 940°C. The number of Ta5+ ions at site B remained constant, whereas the number of Nd3+ ions at site A changed. The degree of deviation from the Curie–Weiss law (∆Tm) and the degree of diffuseness of the ferroelectric relaxors (γ) have a direct and close relationship. Combined analysis of the grain size, phase structure, domain structure, and activation energy (Ea) for domain wall movement was used to understand the mechanism of the piezoelectric improvement in PZT‐based ceramics. The high proportion of the tetragonal phase in the coexisting tetragonal–rhombohedral phases is closely related to the low Ea, which promotes domain rotation and leads to high piezoelectricity. The xNd2O3–PZTMWNN (x = 2.0, 2.5) ceramics have a very low Ea, but the clamping effect caused by the fine grain boundaries hinders the motion of the domain wall. The xNd2O3–PZTMWNN (x = 1.0) ceramics with low Ea, striped nanodomains, and large grains exhibited the highest piezoelectric activity. [ABSTRACT FROM AUTHOR]

A high performance of novel three-component composites with 2–1–2 connectivity is reported and discussed. Layers of the composites are parallel-connected, and each layer contains the ferroelectric (FE) component. The layer of the first type (LFT) represents domain-engineered single crystal poled along either [0 0 1] or [0 1 1]. The layer of the second type is described as a system of long FE ceramic rods that have the shape of an elliptic cylinder and are aligned in a polymer medium. Piezoelectric coefficients d 3 j ∗ and g 3 j ∗ and sets of figures of merit (FOM) (energy-harvesting d 3 j ∗ g 3 j ∗ , modified F 3 j ∗ σ for a stress-driven harvester and modified F 3 j ∗ ξ for a strain-driven harvester) are analyzed to show their large values and specifics of the anisotropy when varying volume fractions of components and a rotation angle of the ceramic rod bases. For the first time, the studied parameters are compared in two directions: (i) the composite based on [0 0 1]-poled single crystal versus the composite based on [0 1 1]-poled single crystal and (ii) the lead-free composite versus the lead-containing composite (both based on [0 0 1]-poled single crystals). The advantages of the high-performance lead-free composite are discussed. The 2–1–2 composites put forward in this paper are of interest as advanced materials suitable for piezoelectric sensors, actuators and energy-harvesting systems operating at constant stress or strain. [ABSTRACT FROM AUTHOR]

This paper studies the structural parameters and electrophysical properties (dielectric and piezo electric, as well as currents of thermostimulated depolarization) of samples of composition 0.20BiScO3·0.45PbTiO3·0.35PbMg1/3Nb2/3O3 (or in short 0.20BS·0.45PT·0.35PMN) obtained by ceramic and melt-hardening methods of synthesis. In the ceramic method, the samples were obtained from the starting oxides by two-stage firing. In the melt method, amorphous precursors were first obtained from heat-treated and non-heat-treated starting oxide mixtures by melting and subsequent quenching under sharply gradient temperature conditions. Samples were obtained after grinding, pressing, and thermal annealing of the synthesized precursors, and four types of samples differing in size and shape of the intermediate precursor particles (crystallites) were obtained. The X-ray phase analysis showed that the predominant phase in the studied samples is the perovskite phase; in both types of samples, up to 5 wt.% of impurity phase with pyrochlore structure was also present. The samples of 0.20BS·0.45PT·0.35PMN exhibit dielectric properties characteristic of relaxor ferroelectrics, and the polarized samples exhibit a pronounced piezo effect with a piezo modulus value of d33~200 pC/N. A comparative analysis of the properties of the samples obtained by different methods has been carried out. The essential advantage of the melt method is that its use allows obtaining varieties of four kinds of ferroelectric relaxors and reduces the time of synthesis of samples by 2–3 times. [ABSTRACT FROM AUTHOR]

Electronic and dielectric properties are essential for understanding many functional materials, predicting their behavior and optimizing their performance across different shapes, geometries and scales. Several approaches were developed and explored to investigate more or less deeply the appropriate properties. One of the most appealing, accurate and efficient approach is first principle simulations based on modern theory of polarization. Especially with the increased availability of powerful computational resources and techniques. Building upon these advancements, our contribution aims to elucidate an efficient methodology for studying electronic and dielectric properties by applying the Berry phase and Maximally Localized Wannier functions methods. Our exploration will initially focus on a systematic study of the electronic, chemical bonding, ferroelectric and piezoelectric properties of the well-known prototypical bulk system PbTiO3. Subsequently, we will extend our study to examine slab properties as surface termination and slab thickness effect on electronic properties, utilizing the robust Wannier-justified Tight Binding model. [ABSTRACT FROM AUTHOR]

This paper studies the structural parameters and electrophysical properties (dielectric and piezo electric, as well as currents of thermostimulated depolarization) of samples of composition 0.20BiScO3·0.45PbTiO3·0.35PbMg1/3Nb2/3O3 (or in short 0.20BS·0.45PT·0.35PMN) obtained by ceramic and melt-hardening methods of synthesis. In the ceramic method, the samples were obtained from the starting oxides by two-stage firing. In the melt method, amorphous precursors were first obtained from heat-treated and non-heat-treated starting oxide mixtures by melting and subsequent quenching under sharply gradient temperature conditions. Samples were obtained after grinding, pressing, and thermal annealing of the synthesized precursors, and four types of samples differing in size and shape of the intermediate precursor particles (crystallites) were obtained. The X-ray phase analysis showed that the predominant phase in the studied samples is the perovskite phase; in both types of samples, up to 5 wt.% of impurity phase with pyrochlore structure was also present. The samples of 0.20BS·0.45PT·0.35PMN exhibit dielectric properties characteristic of relaxor ferroelectrics, and the polarized samples exhibit a pronounced piezo effect with a piezo modulus value of d33~200 pC/N. A comparative analysis of the properties of the samples obtained by different methods has been carried out. The essential advantage of the melt method is that its use allows obtaining varieties of four kinds of ferroelectric relaxors and reduces the time of synthesis of samples by 2–3 times.

The B-site complex BaZr 0.1 Ti 0.9 O 3 (BZT) microplatelets with perovskite-structured were synthesized, using the Bi 4 (Zr 0.1 Ti 0.9) 3 O 12 (BIZ 0.1 T 0.9) as a precursor. The precursor had a high aspect ratio, with an average size of ∼8.0 μm. Later, B-site complex BZT microplatelets were obtained via molten salt methods. The influence of n(BIZ 0.1 T 0.9):n(BaCO 3) ratio and calcined temperature in the composition, morphology and local piezoelectric and ferroelectric behaviour for BZT microplatelets was deeply discussed. The result showed that the reactants ratio determined the supersaturation degree in the molten salt environment, while the calcined temperature determined the crystallinity of BZT microcrystals. Overall, with the n(BIZ 0.1 T 0.9):n(BaCO 3) ratio was 1:4, the BZT microcrystal calcined at 900 °C had a better plate-like morphology. Manwhile, the micropizoelectric properties of BZT microplatelet was studied, achieving a maximum d 33 * of ∼330 pm/V. The result indicated that the B-site complex BZT microplatelets is a potential templates for textured ceramics. [ABSTRACT FROM AUTHOR]

The lead metaniobate (PbNb 2 O 6 , PN) with high Curie temperature is widely used to fabricate transducer for high-temperature application up to 300 °C. However, evident dielectric anomalies and direct-current resistivity degradation were experimentally observed in PN-based ceramics at high temperature, which may significantly restrict the working temperature range for well logging application. When the sample was heat-treated at 260 °C for 3 h in silicon oil, the dc-resistivity of ceramics at 260 °C decreased from 3.8 × 108 to 1.0×107 Ω⋅cm, accompanied by 43 times increase in tan δ at 1 kHz. To investigate the cause of these phenomena, the in-situ piezoelectric, dielectric properties and dc-resistivity were systematically investigated in the samples subjected to heat-treatment at 260 °C in silicon oil. It is revealed that the porous structure of PN-based ceramics allows for the infiltration of silicon oil as a minor phase, and the accumulation of its decomposers within the pores would exert significant influence on the dielectric property and dc-resistivity of ceramics at elevated temperatures. However, the samples still demonstrate excellent thermal stability in piezoelectric property, with value of k t maintaining 0.39 at 260 °C in oil. In addition, the low Q m is not the intrinsic property of PN ceramics, but rather related to the phase transition of silicon oil within pores of ceramics, as indicated by the increase in Q m from 47 to 80 after heat-treatment in air. [ABSTRACT FROM AUTHOR]

Bi0.5Na0.5TiO3 (BNT) emerges as a promising ferroelectric and piezoelectric lead-free candidate to substitute the contaminant Pb[TixZr1−x]O3 (PZT). However, to obtain optimal ferroelectric and piezoelectric properties, BNT must be sintered at high temperatures. In this work, the reduction of sintering temperature by using iron added to BNT is demonstrated, without significant detriment to the dielectric properties. BNT-xFe with iron from x = 0 to 0.1 mol (∆x = 0.025) were synthesized using high-energy ball milling followed by sintering at 900 °C. XRD analysis confirmed the presence of rhombohedral BNT together with a new phase of NaFeTiO4 (NFT), which was also corroborated using optical and electronic microscopy. The relative permittivity, in the range of 400 to 500 across all the frequencies, demonstrated the stabilization effect of the iron in BNT. Additionally, the presence of iron elevates the transition from ferroelectric to paraelectric structure, increasing it from 330 °C in the iron-free sample to 370 °C in the sample with the maximum iron concentration (0.1 mol). The dielectric losses maintain constant values lower than 0.1. In this case, low dielectric loss values are ideal for ferroelectric and piezoelectric materials, as they ensure minimal energy dissipation. Likewise, the electrical conductivity maintains a semiconductor behavior across a range of 50 Hz to 1 × 106 Hz, indicating the potential of these materials for applications at different frequencies. Additionally, the piezoelectric constant (d33) values decrease slightly when low concentrations of iron are added, maintaining values between 30 and 48 pC/N for BNT-0.025Fe and BNT-0.05Fe, respectively. [ABSTRACT FROM AUTHOR]

BiFeO 3 -BaTiO 3 (BF-BT) ceramics are an excellent choice for high-temperature lead-free piezoelectric ceramic due to their high Curie temperature and good piezoelectric properties, but the volatilization of Bi leads to the formation of A-site cationic vacancies and oxygen vacancies, culminating in heightened leakage currents and detrimental effects on piezoelectric properties. In this study, a chemical composition of 0.70Bi (1+ x) Fe 0·97 Al 0·03 O 3 -0.30BaTiO 3 ceramics, abbreviated as B 1+ x FA-BT, where 0 ≤ x ≤ 0.05, were synthesized, with special attention on the effects of Bi compensation and poling process on their insulation and piezoelectric properties. Due to the coexistence of R - PC phases and low leakage current, B 1+ x FA-BT ceramics exhibit excellent piezoelectric properties and high Curie temperature, among which the B 1.02 FA-BT ceramic boasts optimal overall properties: d 33 = 196 pC N−1, T C = 480 °C, k p = 34%, θ max = 49.5° and Q m = 32, under optimal poling parameters E p = 50 kV cm−1 and T p = 100 °C. The poling process is directly linked to the reorientation of domains, the redistribution of positive/negative space charge and the aggregation or injection of holes, which is achieved by tuning the poling field and temperature in a ceramic with optimal integrated piezoelectric properties. The poling process of BF-BT ceramics is significantly influenced by their leakage characteristics, which can have a significant impact on their overall performance. Optimizing electrical poling conditions and minimizing leakage current is crucial to achieving favorable piezoelectric properties in BF-BT ceramics with R - PC coexisting structures. [ABSTRACT FROM AUTHOR]

The effect of calcination process on a phase evolution, a microstructure development and the piezoelectric properties were investigated in 0.75BiFeO 3 -0.25BaTiO 3 (0.75BF-0.25BT) ceramics. At the relatively low calcination temperatures of 600 °C–650 °C, a Bi 25 FeO 40 impurity phase was formed in addition to some unreacted raw materials and a perovskite phase. As the calcination temperature increased to the range of 700–900 °C, other intermediate phase BaBi 4 Ti 4 O 15 was formed concurrently with small amounts of unreacted BaCO 3 and perovskite matrix phase. At 950 °C a pure single perovskite phase of 0.75BF-0.25BT solid solution was observed. The sintered samples produced by using the raw powder calcined at a relatively low temperature of 600–900 °C showed a large fraction of pseudo-cubic relaxor phase (0.54–0.71 mass fraction) with the rest of a rhombohedral ferroelectric phase. They showed poor piezoelectric properties at sintering temperature below 1000 °C due to the nonuniform compositional distribution of the calcined powder. The homogeneous calcination at 950 °C for 2 h reduced greatly the optimum sintering temperature and significantly enhanced piezoelectric properties in the BF-BT ceramics. High Curie temperature as well as high piezoelectric properties were obtained at the sintering temperature as low as 920 °C: k p = 0.361, d 33 = 123 pC/N and T C = 653 °C in the 0.75BF-0.25BT ceramics and k p = 0.337, d 33 = 183 pC/N and T C = 525 °C in the 0.7BF-0.3BT ceramics. This low temperature sintering of the BF-BT ceramics by a homogeneous calcination could be applied to the fabrication of the lead-free multi-layer piezoelectric devices with inexpensive internal electrodes. [ABSTRACT FROM AUTHOR]

The piezoelectric and electromechanical coupling coefficients in conjunction with their temperature stability are the crucial figure-of-merits of piezoelectric materials, due to these properties determine their response sensitivity and operating temperature range, respectively for practical applications. In this work, Sb, (Bi 0.5 Na 0.5)ZrO 3 , and (Bi 0.5 K 0.5)HfO 3 were used to regulate phase transition of KNN-based ceramics, and resultant large piezoelectric constants d 33 ∼ 430 ± 10 pC/N, unipolar strain S uni ∼ 0.18 % at 40 kV/cm, and a high planar electromechanical coupling factor k p ∼ 55 % were observed in the composition with rhombohedral-orthorhombic-tetragonal (R-O-T) multiphase coexistence. Ex-situ electric field XRD measurement and TEM observation indicate the outstanding piezoelectric properties are originated from the electric field-induced phase transition, nanodomains and polar nanoregions, which lower polarization anisotropy and facilitate polarization rotation between different crystallographic symmetries. In addition, the piezoelectric properties of the samples with R-O-T phases coexistence show superior temperature stability and fatigue resistance after 106 bipolar electric cycles. The present study not only helps to understand the structural origin of high piezoresponse, but also lays a foundation for the applications of KNN-based ceramics. [ABSTRACT FROM AUTHOR]

Traditional piezoelectric materials cause serious environmental and health issues because of their lead–containing substances, and thus lead–free piezoelectric ceramics would have many applications. In this study, we successfully prepared the lead–free ceramics (1- x) (K 0 · 48 Na 0 · 48 Li 0.04) (Nb 0 · 975 Sb 0.025)O 3 – x (Bi 0 · 5 Na 0.5) (Zr 0 · 8 Ti 0.2)O 3 ((1- x)KNLNS– x BNZT, x = 0, 0.005, 0.0075, 0.01, 0.015, 0.02 and 0.03) with rhombohedral–tetragonal (R–T) phase coexistence near room temperature, employing con–entional solid sintering. The minimum cell volume of the ceramics and R–T phase coexistence in them were achieved at a doping amount x = 0.01, which facilitated the optimal performance of the ceramics (d 33 ∼467 pC/N ± 14 pC/N, T c∼272 °C, ε r ∼1676, k p ∼0.42, where d 33 : piezoelectric constant; T c: Curie temperature; ε r : dielectric constant; k p : electromechanical coefficient). The ceramics exhibited microstructures with high density and low porosity and had a maximum relative density of 95.68 %. At x = 0.01, the ceramics exhibited a uniformly distributed small domain structures with nanodomains, accounting for their high-voltage electrical properties. Because these stable and reliable piezoelectric (1- x)KNLNS– x BNZT ceramics exhibit excellent electrical performance, they can replace lead–based materials. The direct solid–phase sintering method provides prospects for the large–scale application of the lead–free piezoelectric ceramics. The 0.99(K 0 · 48 Na 0 · 48 Li 0.04)(Nb 0 · 975 Sb 0.025)O 3 –0.01(Bi 0 · 5 Na 0.5)(Zr 0 · 8 Ti 0.2)O 3 ceramics exhibit excellent piezoelectric properties owing to their nanodomain structures, rhombohedral–tetragonal coexistence phase boundaries at room temperature (25°C ± 5°C) and dense microstructures. [Display omitted] [ABSTRACT FROM AUTHOR]

In the area of flexible electronics, pressure sensors are a widely utilized variety of flexible electronics that are both indispensable and prevalent. The importance of pressure sensors in various fields is currently increasing, leading to the exploration of materials with unique structural and piezoelectric properties. Perovskite-based materials are ideal for use as flexible pressure sensors (FPSs) due to their flexibility, chemical composition, strain tolerance, high piezoelectric and piezoresistive properties, and potential integration with other technologies. This article presents a comprehensive study of perovskite-based materials used in FPSs and discusses their components, performance, and applications in detecting human movement, electronic skin, and wireless monitoring. This work also discusses challenges like material instability, durability, and toxicity, the limited widespread application due to environmental factors and toxicity concerns, and complex fabrication and future directions for perovskite-based FPSs, providing valuable insights for researchers in structural health monitoring, physical health monitoring, and industrial applications. [ABSTRACT FROM AUTHOR]

Strain engineering is a crucial approach in the engineering field to optimize various physical properties of materials by applying mechanical strain loading. However, it is extremely challenging to find out the best conditions of strain with unprecedented physical properties in the vast strain space consisting of six components. Here, we developed a technical framework that enables efficient exploration of physical properties in the vast strain space based on machine learning (i.e., artificial neural networks), active learning, and high-throughput first-principles calculation. We demonstrated the active learning technique to successfully and efficiently construct an accurate machine learning model for ferroelectric PbTiO3 with minimal first-principles datasets (only 3.7% of the vast strain-space). Our machine learning model can accurately predict the nonlinear mechanical deformation and electromechanical response in the three components of normal strain loading. We also carried out strain optimization of piezoelectric response using the machine learning model and found that a large piezoelectric response is five times larger than without strain loading. We showed that the physical property explorer framework constructed in this study makes it possible to optimize strain for various material properties in a vast strain space by calculating only a small number of data points. These results suggest paving the way for constructing nonlinear piezoelectric constitutive equations for novel piezoelectric devices via strain engineering.

A high performance of novel three-component composites with 2–1–2 connectivity is reported and discussed. Layers of the composites are parallel-connected, and each layer contains the ferroelectric (FE) component. The layer of the first type (LFT) represents domain-engineered single crystal poled along either [0 0 1] or [0 1 1]. The layer of the second type is described as a system of long FE ceramic rods that have the shape of an elliptic cylinder and are aligned in a polymer medium. Piezoelectric coefficients [Formula: see text] and [Formula: see text] and sets of figures of merit (FOM) (energy-harvesting [Formula: see text], modified [Formula: see text] for a stress-driven harvester and modified [Formula: see text] for a strain-driven harvester) are analyzed to show their large values and specifics of the anisotropy when varying volume fractions of components and a rotation angle of the ceramic rod bases. For the first time, the studied parameters are compared in two directions: (i) the composite based on [0 0 1]-poled single crystal versus the composite based on [0 1 1]-poled single crystal and (ii) the lead-free composite versus the lead-containing composite (both based on [0 0 1]-poled single crystals). The advantages of the high-performance lead-free composite are discussed. The 2–1–2 composites put forward in this paper are of interest as advanced materials suitable for piezoelectric sensors, actuators and energy-harvesting systems operating at constant stress or strain.

Abstract The crystal of [C(NH2)3]2Zn(SO4)2 guanidine zinc sulfate was grown and its structure, dilatometric, dielectric, elastic and piezoelectric properties were studied in a broad temperature range, covering the phase transition point. The crystal undergoes a continuous phase transition at 178 K from the room temperature tetragonal phase with a space group $$\text{I}\overline{4}2\text{d }$$ I 4 ¯ 2 d to the tetragonal low temperature phase with a space group $$\text{I}\overline{4 }$$ I 4 ¯ . The structural X-ray studies allowed proposing molecular mechanism associated with the rearrangement in the configuration of N–H⋯O hydrogen bonds and reorientation of guanidine cations in the structure, leading to a change in the symmetry of the low temperature phase. Results of thermal expansion and dielectric studies are typical of a structural nonferroelectric continuous transition. Also measurement of piezoelectric and elastic properties revealed small anomalies at 178 K. Below the transition temperature, a new piezoelectric component, that is a ferroelastoelectric macroscopic order parameter, was found.

Flexible electronic components such as wearable sensors, energy harvesting devices, and human health monitoring systems based on piezoelectric materials have garnered significant attention within the scientific community. In this study, PZT nanofibers were modified with dopamine hydrochloride prior to their integration into PVDF fibers, serving as piezoelectric reinforcements to enhance the mechanical and piezoelectric characteristics of composite fiber films. Subsequently, a facile hot-pressing method was employed to fabricate multilayered films characterized by a densely packed surface fiber arrangement and a loosely organized internal fiber orientation, which markedly improved the self-supporting ability and fiber density of the electrospun fiber films. A detailed investigation into the micro-morphology, crystallinity, and enhanced piezoelectric properties of the films was conducted. Notably, the composite fiber film containing 6 wt% PZT NFs exhibited a peak piezoelectric coefficient (d 33) of 29 pC/N, resulting in an output voltage of 13.8 V. This represents a 2.23-fold enhancement in d 33 value and a 4.6-fold increase in output voltage when compared to the pristine PVDF fiber film, which had a d 33 of 13 pC/N and an output voltage of 3 V. The power density achieved by the sensor is 0.73 μW/cm2. This performance is underpinned by a high piezoelectric coefficient, outstanding output characteristics, and robust stability, which collectively enhance the sensor's efficacy in various applications. This research presents an effective approach for augmenting the piezoelectric performance of PVDF-based composite films and paves the way for the advancement of piezoelectric energy harvesting applications. [ABSTRACT FROM AUTHOR]

Films of piezoelectric poly(vinylidene fluoride) (PVDF) and its copolymer P(VDF-TrFE) have been studied intensively for their potential application in piezoelectric sensing devices. The present work focuses on tuning the piezoelectric properties of P(VDF-TrFE) films via incorporating Ag and polydopamine co-decorated PZT (Ag@PDA@PZT) particles. Ag@PDA@PZT particles can effectively improve the β-phase content and piezoelectric properties of P(VDF-TrFE) films. The highest open-circuit voltage and short-circuit current of P(VDF-TrFE)-based flexible pressure sensors incorporating Ag@PDA@PZT particles are ~30 V and ~2.4 μA, respectively. The flexible sensors exhibit a response to different body movements, providing a practical and potentially useful basis for human−machine interface applications. [ABSTRACT FROM AUTHOR]

The crystal of [C(NH2)3]2Zn(SO4)2 guanidine zinc sulfate was grown and its structure, dilatometric, dielectric, elastic and piezoelectric properties were studied in a broad temperature range, covering the phase transition point. The crystal undergoes a continuous phase transition at 178 K from the room temperature tetragonal phase with a space group I 4 ¯ 2 d to the tetragonal low temperature phase with a space group I 4 ¯ . The structural X-ray studies allowed proposing molecular mechanism associated with the rearrangement in the configuration of N–H⋯O hydrogen bonds and reorientation of guanidine cations in the structure, leading to a change in the symmetry of the low temperature phase. Results of thermal expansion and dielectric studies are typical of a structural nonferroelectric continuous transition. Also measurement of piezoelectric and elastic properties revealed small anomalies at 178 K. Below the transition temperature, a new piezoelectric component, that is a ferroelastoelectric macroscopic order parameter, was found. [ABSTRACT FROM AUTHOR]

Recently, high-performance lead zirconate titanate (Pb( Zr 1 − x Tix)O3, PZT) ferroelectric ceramics have attracted intensive attention due to their wider operating temperature range, better temperature stability, as well as larger piezoelectric properties and higher energy conversion efficiency. In this study, the perovskite-type ferroelectric ceramics with a chemical formula of Pb 0. 9 9 − x Gd 0. 0 1 Srx Zr 0. 5 3 Ti 0. 4 7 O3 (x = 0 and 0.02, abbr. PGZT and PGSZT, respectively) were prepared by the traditional solid-state reaction route. The influences of Sr-doping on the phase structure, dielectric properties, ferroelectric properties and piezoelectric properties of the PGZT ceramics were comprehensively investigated. The field-dependent P–E hysteresis loops of PGSZT were measured in the frequency range of 0.05–10 Hz and temperature range of 20–100∘C. The results show that Sr-doping not only enhances the dielectric permittivity and piezoelectric coefficient of PGZT, but also decreases its dielectric loss tangent, with the d 3 3 value of 473 pC/N, ε r value of 1586 and tan δ value of 0.016 found in PGSZT. Also, PGSZT shows a high Curie temperature ( T C ) of 3 5 0 ∘ C. The underlying mechanisms of the property enhancement were identified as that the introduced Sr 2 + replaces the volatile Pb 2 + located at the A-site of the perovskite structure, thereby reducing the concentration of lead vacancies and promoting the grain growth of the ceramics, consequently enhancing the dielectric and piezoelectric properties of PGZT. On the other hand, the frequency change in the low-frequency range (< 1 Hz) played a significant impact on the remanent polarization ( P r ) and internal biased electric field ( E i ) of PGSZT, but the frequency dependence of coercive field ( E c ) tends to diminish in the high-frequency range (≥ 1 Hz). [ABSTRACT FROM AUTHOR]

Pb(Mg 0. 5 W 0. 5 )O3–Pb(Ni 1 ∕ 3 Nb 2 ∕ 3 )O3–Pb(Zr 0. 5 Ti 0. 5 )O3 (PNN–PMW–PZT) piezoceramics were sintered at a low temperature of 900∘C by the mixed metal oxide powder solid-state reaction route. CaCO3 and Li2CO3 as sintering aids and Yb2O3 as a dopant were added into the PNN–PMW–PZT ceramic system for low-temperature sintering and enhancement of electrical properties, respectively. The effects of different Yb2O3 doping amounts on the microstructure, dielectric, piezoelectric and ferroelectric properties of the samples were systematically investigated. The piezoceramics doped with 0.1 mol% Yb2O3 have optimal electrical properties ( d 3 3 = 5 6 3 pC/N, k p = 0. 6 6 , ε r = 2 7 2 8 (1 kHz), tan δ = 0. 0 1 7 6 (1 kHz), and T C = 3 0 1 ∘ C). While the piezoceramics doped with 0.3 mol% Yb2O3 have optimal energy conversion properties: the piezoelectric voltage coefficient g 3 3 = 2 6. 7 × 1 0 − 3 Vm/N and the effective piezoelectric energy conversion coefficient d 3 3 × g 3 3 = 1 4 3 6 6 × 1 0 − 1 5 m2/N. [ABSTRACT FROM AUTHOR]

The perovskite-structured materials P b 0.75 B a 0.25 1 − x C a x (Z r 0.7 T i 0.3) O 3 for x = 1 and 2 at.% were synthesized using the conventional mixed-oxide method and carbonates. Microstructural analysis, performed using a scanning electron microscope, revealed rounded grains with relatively inhomogeneous sizes and distinct grain boundaries. X-ray diffraction confirmed that the materials exhibit a rhombohedral structure with an R3c space group at room temperature. Piezoelectric resonance measurements were conducted to determine the piezoelectric and elastic properties of the samples. The results indicated that a small amount of calcium doping significantly enhanced the piezoelectric coefficient d31. The calcium-doped ceramics exhibited higher electrical permittivity across the entire temperature range compared to the pure material, as well as a significant value of remanent polarization. These findings indicate that the performance parameters of the base material have been significantly improved, making these ceramics promising candidates for various applications. [ABSTRACT FROM AUTHOR]

CaBi 2 Nb 2 O 9 (CBN) with the Aurivillius phase has a high Curie temperature (T C) and remarkable fatigue resistance, which has great potential for application as high-temperature sensors. However, due to its low piezoelectric properties, its practical application remains a great challenge. In this paper, Ca 1- x Ce x Bi 2 Nb 2 O 9 ceramics were prepared by the direct reaction sintering (DRS) and conventional preparation (CP) methods, respectively. The experimental results indicate that Ce doping can increase the piezoelectric coefficient d 33 of CBN ceramics by about two times. Among them, the grain size of the samples prepared by the DRS method is finer and more uniform, and the d 33 value of DRS samples is about 3.6–9.4 % higher than that of CP samples. The DRS sample Ca 0·97 Ce 0·03 Bi 2 Nb 2 O 9 has a d 33 value of 18.9 pC/N, a T C of 948 °C, and a resistivity of 1.1 × 105 Ω cm at 600 °C. This study shows that DRS method is an effective densification method, which can prepare CBN-based ceramics with excellent comprehensive properties, and provides an innovative preparation route to explore CBN-based ceramics with excellent piezoelectric properties. [ABSTRACT FROM AUTHOR]

Piezoelectric temperature stability is often a very important item for piezoelectric materials when putting them into practical applications like filters and ultrasonic transducers. Phase transitions of (K,Na)NbO 3 -based compositions that contain neither toxic Pb nor Sb elements were tailored to simultaneously acquire enhanced piezoelectric properties and good piezoelectric temperature stability in this study. Specifically, dense 0.94(K 0.48 Na 0.52)NbO 3 -0.03BaZrO 3 -0.01BaSnO 3 -0.02(Bi 0.5 Na 0.5)ZrO 3 ceramic and its further compositionally modified one by 1 wt% MnO 2 were prepared. Both of these two ceramics display quite weak piezoelectric temperature dependence in the usage temperature range between −30 °C–100 °C, but the one modified by MnO 2 has the significantly improved piezoelectric properties with a high piezoelectric coefficient d 33 of 310 pC/N and large electromechanical coupling factors k p and k 33 of 0.57 and 0.73 at room temperature. The obtained excellent piezoelectric performance is considered to be associated closely with the stable piezoelectric characteristic of the orthorhombic phase and the diffused rhombohedral-orthorhombic and orthorhombic-tetragonal phase transitions. [ABSTRACT FROM AUTHOR]

Bi 3 Ti 1.5 W 0.5 O 9 –Bi 4 Ti 3 O 12 intergrowth Aurivillius piezoceramics with 0.3mol Nb5+ replacing B site and x mol CeO 2 (x = 0–0.25, abbreviated as BTNW-BITN- x Ce) replacing A site were synthesized by the conventional solid-state reaction method. The structures and electrical properties of BTNW-BITN- x Ce samples were systematically explored. The results of XRD, Raman, and SEM showed that a single phase was formed. The results of XPS showed that the introduction of Ce ions reduces the concentration of oxygen vacancies, which is beneficial to improving piezoelectric performance. In addition, the results of PFM indicated that the introduction of Ce ions increased the diversity of domains and made it easier for domains to respond under the same voltage, which is also conducive to the improvement of piezoelectric properties. The d 33 of the optimal component BTNW-BITN- x Ce ceramics is 23.6 pC/N and it possesses 21.6 pC/N after 500 °C annealing treatment, which implies potential in the application of high-temperature sensors. [ABSTRACT FROM AUTHOR]

Liquid phase sintering aids play an important role in facilitating grain growth and promoting texture formation. However, these sintering aids remain at grain boundaries after sintering, leading to a deterioration in the properties and hindering the reproducibility of textured ceramics. In this study, we employed the templated grain growth (TGG) method to synthesize [001]-textured Pb(Mg 1/3 Nb 2/3)O 3 –PbZrO 3 –PbTiO 3 (PMN-PZT) piezoelectric ceramics, and implemented a crucial post-annealing step to remove the residual PbO. The effect of annealing temperatures on the microstructure, dielectric and piezoelectric properties of the textured ceramics was investigated. The results demonstrate the substantial influence of annealing temperature on these properties. Specifically, annealing at 800 °C led to a significant enhancement, with the ε r at room temperature increasing from 2277 to 2410, and the k 33 improving from 0.85 to 0.88. Consequently, the d 33 increases from 1080 to 1220 pC/N. This study emphasizes the effectiveness of the post-annealing treatment in improving the properties and reproducibility of textured piezoelectric ceramics, which is particularly crucial for the mass production of textured ceramics. [ABSTRACT FROM AUTHOR]

In the present work, hybrid nanocomposites of an epoxy resin reinforced with ZnTiO3 and BaTiO3 nanoparticles, at various filler contents, were fabricated and studied. The successful integration of ceramic nanofillers and the fine distribution of nanoparticles were confirmed via X-ray Diffraction patterns and Scanning Electron Microscopy images, respectively. Dielectric properties and related relaxation phenomena were investigated via Broadband Dielectric Spectroscopy in a wide range of frequencies and temperatures. Data analysis showed that dielectric permittivity increases with filler content, although optimum performance does not correspond to the maximum ZnTiO3 content. Four relaxation processes were observed and attributed to interfacial polarization (IP) (at low frequencies and high temperatures), glass-to-rubber transition (α-relaxation) of the epoxy matrix (at intermediate frequencies and temperatures), and local rearrangements of polar side groups of the macromolecules (β-relaxation) and small flexible groups of the main polymer chain (γ-relaxation) occurring at low temperatures and high frequencies. The ability of hybrid nanocomposites to store and retrieve energy was studied under dc conditions by employing a charging/discharging sequence. The stored and retrieved energy increases with filler content and charging voltage. The optimum ability of energy recovering, shown by the epoxy/7 phr ZnTiO3/7 phr BaTiO3 nanocomposite, ranges between 30 and 50 times more than the matrix, depending on the time instant. The employed nanoparticles induce piezoelectric properties in the nanocomposites, as found by the increase in the piezoelectric coefficient with filler content. [ABSTRACT FROM AUTHOR]

Single zinc oxide nanowires (ZnO NWs) are promising for nanogenerators because of their excellent semiconducting and piezoelectric properties, but characterizing the latter efficiently is challenging. As reported here, an electrical breakdown strategy was used to construct single ZnO NWs with a specific length. With the high operability of a nanomanipulator in a scanning electron microscope, ZnO-NW-based two-probe and three-probe structures were constructed for fabricating AC/DC nanogenerators, respectively. For a ZnO NW, an AC output of between −15.31 mV and 5.82 mV was achieved, while for a DC nanogenerator, an output of ∼24.3 mV was realized. Also, the three-probe structure's output method was changed to verify the distribution of piezoelectric charges when a single ZnO NW is bent by a probe, and DC outputs of different amplitudes were achieved. This study provides a low-cost, highly convenient, and operational method for studying the AC/DC output characteristics of single NWs, which is beneficial for the further development of nanogenerators. ARTICLE HIGHLIGHTS: HIGHLIGHTS • A method for reworking NWs to a specific length was achieved using an electrical breakdown strategy based on the constructed electrical loop, and its success rate is high. • With the maneuverability provided by multiple operating units of a nanomanipulator, AC output was investigated for a single ZnO NW with a two-probe structure, as well as DC output with a three-probe structure. • In the three-probe structure, different DC outputs were achieved by changing the position of the NW–probe contact point and the wiring state of the probe, while the distribution of surface piezoelectric potential along the NW's axis was studied. [ABSTRACT FROM AUTHOR]