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Defect-relevant piezoelectric and ferroelectric properties in LiCuTa3O9-doped K0.5Na0.5NbO3 lead-free piezoceramics
摘要： Lead-free K0.5Na0.5NbO3 + x mol LiCuTa3O9 (abbreviated to KNN-xLCT) piezoceramics are synthesized via a conventional sintering technique. All ceramics exhibit perovskite structure and their densification is improved after the addition of LCT. The doping of small quantities of LCT (x ≤ 0.015) results in the generation of two sorts of defect complexes [i.e., ?? V??(Cu???o ) ], inducing greatly hardening electrical behaviors with high mechanical quality factor Qm of ~ 780 at x = 0.015. However, excess LCT (x ≥ 0.015) contributes to the substantial reduction of defect complexes, and thus the ceramics are softened, presenting a relatively low Qm of ~ 480 at x = 0.03. It is noted that the ceramics with x = 0.03 remain comparatively great piezoelectric performances: d33 = 96 pC/N and kp = 37%. Our study indicates that the electrical properties of KNN-based ceramics doped with LCT are closely related with microscopic defect structure in the materials.
关键词： Lead-free piezoceramics,K0.5Na0.5NbO3,Piezoelectric properties,Defect complexes,LiCuTa3O9
更新于2025-09-23 15:19:57
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Lead-free all-inorganic cesium tin iodide perovskite for filamentary and interface-type resistive switching toward environment-friendly and temperature-tolerant nonvolatile memories
摘要： Recently, organometallic and all-inorganic halide perovskites (HPs) have become promising materials for resistive switching (RS) nonvolatile memory devices with low-power consumption, because they show current–voltage hysteresis caused by fast ion migration. However, the toxicity and environmental pollution potential of lead, a common constituent of HPs, has limited commercial applications of HP-based devices. Here, RS memory devices based on lead-free all-inorganic cesium tin iodide (CsSnI3) perovskites with temperature-tolerance are successfully fabricated. The devices exhibit reproducible and reliable bipolar RS characteristics in both Ag and Au top electrodes (TEs) with different switching mechanisms. The Ag TE devices show filamentary RS behavior with ultra-low operating voltages (< 0.15 V). In contrast, the Au TE devices have interface-type RS behavior with gradual resistance changes. This suggests that the RS characteristics are attributed to either the formation of metal filaments or the ion migration of defects in HPs under applied electric fields. These distinct mechanisms may permit the opportunity to design devices for specific purposes. This work will pave the way for lead-free all-inorganic HP-based nonvolatile memory for commercial applications of HP-based devices.
关键词： valence change mechanism,electrochemically metallization,all-inorganic halide perovskite,lead-free halide perovskite,resistive switching memory
更新于2025-09-19 17:15:36
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Air-Stable, Lead-Free Zero-Dimensional Mixed Bismuth-Antimony Perovskite Single Crystals with Ultrabroad Band Emission
摘要： Lead-free zero-dimensional (0D) organic-inorganic metal halide perovskites have recently attracted increasing attention for their excellent photoluminescence properties and chemical stability. Here, we report the synthesis and characterization of an air-stable 0D mixed metal halide perovskite (C8NH12)4Bi0.57Sb0.43Br7.H2O, in which individual [BiBr6]3- and [SbBr6]3- octahedral units are completely isolated and surrounded by the large organic cation C8H12N+. Upon photoexcitation, the bulk crystals exhibit ultrabroad band emission ranging from 400 to 850 nm, which originates from both free excitons and self-trapped excitons. This is the first example of 0D perovskites with broadband emission spanning the entire visible spectrum. In addition, (C8NH12)4Bi0.57Sb0.43Br7.H2O exhibits excellent humidity and light stability. These findings present a new direction towards the design of environmentally-friendly, high-performance 0D perovskite light emitters.
关键词： lead-free,bismuth,antimony,photoluminescence,zero-dimensional perovskites
更新于2025-09-19 17:15:36
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Characteristics of the Structural State of Bismuth Ions in Bismuth-Borate Glasses
摘要： The properties and graphical plots of the properties of bismuth-borate glasses in a wide range of compositions — 20 to 80 mol.% Bi2O3 — are presented. In multi-bismuth glasses both the boron and bismuth ions are found in two coordination states: B3+, B4+ and Bi3+, Bi6+. The [BiO3] groups play the role of a conventional glass former but manifest weakly in the IR spectra.
关键词： structure of bismuth-borate glasses,properties of bismuth-borate glasses,lead-free low-melting glasses,structural role of Bi ions
更新于2025-09-19 17:15:36
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Superior and Anti-fatigue Electro-strain in Bi <sub/>0.5</sub> Na <sub/>0.5</sub> TiO <sub/>3</sub> -based Polycrystalline Relaxor Ferroelectrics
摘要： For eco-friendly bismuth sodium titanate (Bi0.5Na0.5TiO3)-based materials, ultrahigh poling strain (Spol) is always accompanied with a sizable remnant strain (Srem), which severely restricts the cycling reliability of their superior electro-strain. Composition engineering is an effective way of eliminating Srem, but Spol will be sacrificed as well, leading to the overall inferior electro-strain. Here, by composition engineering and subtle criticality confinement, a giant recoverable electro-strain (S>0.7%, realizing the Srem modulation without Spol sacrifice) with reduced hysteresis is reported in BNT-based relaxor ferroelectrics, which can be kept at a high level (<2% variation) even after 105 fatigue cycles. As disclosed by the detailed electric field-dependent multi-scales analyses, the electro-strain behaviors are tightly associated with the agglomeration and deagglomeration process of polar clusters. More efficient release of mechanical mismatch stress among interacting polar entities is suggested to facilitate the deagglomeration process of polar clusters, ensuring a faster restoration of the electric field-induced ferroelectric state when the electric field is removed, which is responsible for the reduced hysteresis and the excellent fatigue performance. These results indicate the significance of 'subtle criticality confinement', and the insight for the design of polycrystalline ceramics with giant and anti-fatigue electro-strain may be useful to develop the new generation of eco-friendly actuators.
关键词： Lead-free Bi0.5Na0.5TiO3,Subtle criticality,Relaxor ferroelectrics,Giant and anti-fatigue electro-strain
更新于2025-09-19 17:15:36
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Outstanding Piezoelectric Performance in Lead-Free 0.95(K,Na)(Sb,Nb)O <sub/>3</sub> -0.05(Bi,Na,K)ZrO <sub/>3</sub> Thick Films with Oriented Nanophase Coexistence
摘要： Lead-free 0.95(K0.48Na0.52)(Nb0.95Sb0.05)O3-0.05Bi0.5(Na0.82K0.18)0.5ZrO3 (KNSN-BNKZ0.05) piezoelectric films with preferred crystal orientation and enhanced thickness are fabricated on silicon substrates from a chemical solution approach. Adequate K excess is introduced to obtain a single perovskite phase in the resulting thicker films. The effects of thickness, crystal orientation, and structure of the films on the performance are investigated. Outstandingly large effective piezoelectric strain coefficient up to 250 pm V?1 is demonstrated over a macroscopic scale using a laser scanning vibrometer in the [100]-KNSN-BNKZ0.05 film with an enhanced thickness of 2.7 μm, competitive to the benchmark oriented lead zirconate titanate films on silicon. Atomically resolved electron microscopy reveals the coexistence of oriented ferroelectric rhombohedral (R) and tetragonal (T) phases at the nanometer scale with gradual polarization rotation, which can lower the domain wall energy and facilitate the large piezoelectric response. The increased film thickness reduces the in-plane mechanical clamping to enable more free deformation in the thickness direction and improve domain wall mobility, both further contributing to enhanced piezoelectric response.
关键词： orientation,sodium potassium niobate,piezoelectric films,phase coexistence,lead-free electronics
更新于2025-09-19 17:15:36
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Linear-like lead-free relaxor antiferroelectric (Bi0.5Na0.5)TiO3-NaNbO3 with giant energy-storage density/efficiency and super stability against temperature and frequency
摘要： A novel lead-free polar dielectric ceramic with linear-like polarization responses was found out in (1-x)(Bi0.5Na0.5)TiO3-xNaNbO3 ((1-x)BNT-xNN) solid solutions, exhibiting giant energy storage density/efficiency and super stability against temperature and frequency. High-resolution transmission electron microscopy, Raman scattering and Rietveld refinements of x-ray diffraction data suggest that these property characteristics be derived from temperature and electric field insensitive large permittivity as a result of relaxor antiferroelectricity (AFE) with polar nanoregions. Additionally, this feature intrinsically requires high driving field for AFE to ferroelectric (FE) phase transitions due to large random fields. Measurements of temperature-dependent permittivity and polarization versus electric field hysteresis loops indicate that high-temperature AFE P4bm phase in BNT was gradually stabilized close to room temperature, accompanying a phase transition from relaxor rhombohedral FEs to relaxor tetragonal AFEs approximately at x=0.15-0.2. A record high for recoverable energy-storage density W~7.02 J/cm3 as well as a high efficiency η~85% was simultaneously achieved in the x=0.22 bulk ceramic, which challenges the existing fact that W and η must be seriously compromised. Furthermore, desirable W (?3.5 J/cm3) and η (?88%) with a variation of less than 10% can be accordingly obtained in the temperature range of 25-250 oC and frequency range of 0.1-100 Hz. These excellent energy-storage properties would make BNT-based lead-free AFE ceramic systems be a potential candidate applied for pulsed power systems.
关键词： Relaxor antiferroelectric,Dielectric,Energy storage,Polar nanoregions,Lead-free ceramics
更新于2025-09-19 17:15:36
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A data-driven framework to predict the morphology of interfacial Cu6Sn5 IMC in SAC/Cu system during laser soldering
摘要： A data-driven approach combining together the experimental laser soldering, finite element analysis and machine learning, has been utilized to predict the morphology of interfacial intermetallic compound (IMC) in Sn-xAg-yCu/Cu (SAC/Cu) system. Six types of SAC solders with varying weight proportion of Ag and Cu, have been processed with fiber laser at different magnitudes of power (30-50 W) and scan speed (10-240 mm/min), and the resultant IMC morphologies characterized through scanning electron microscope are categorized as prismatic and scalloped ones. For the different alloy composition and laser parameters, finite element method (FEM) is employed to compute the transient distribution of temperature at the interface of solder and substrates. The FEM-generated datasets are supplied to a neural network that predicts the IMC morphology through the quantified values of temperature dependent Jackson parameter (αJ). The numerical value of αJ predicted from neural network is validated with experimental IMC morphologies. The critical scan speed for the morphology transition between prismatic and scalloped IMC is estimated for each solder composition at a given power. Sn-0.7Cu having the largest critical scan speed at 30 W and Sn-3.5Ag alloy having the largest critical scan speed at input power values of 40 W and 50 W, thus possessing the greatest likelihood of forming prismatic interfacial IMC during laser soldering, can be inferred as most suitable SAC solders in applications exposed to shear loads.
关键词： Neural network,Intermetallic compound,Lead-free solders,Finite element method (FEM),Laser parameters,Morphology
更新于2025-09-19 17:13:59
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Dependence of material properties and photovoltaic performance of triple cation tin perovskites on the iodide to bromide ratio
摘要： In this work, the influence of a partial introduction of bromide (x = 0–0.33) into MA0.75FA0.15PEA0.1Sn(BrxI1?x)3 (MA: methylammonium, FA: formamidinium, PEA: phenylethylammonium) triple cation tin perovskite on the material properties and photovoltaic performance is investigated and characterized. The introduction of bromide shifts the optical band gap of the perovskite films from 1.29 eV for the iodide-based perovskite to 1.50 eV for the perovskite with a bromide content of x = 0.33. X-ray diffraction measurements reveal that the size of the unit cell is also gradually reduced based on the incorporation of bromide. Regarding the photovoltaic performance of the perovskite films, it is shown that already small amounts of bromide (x = 0.08) in the perovskite system increase the open circuit voltage, short circuit current density and fill factor. The maximum power conversion efficiency of 4.63% was obtained with a bromide content of x = 0.25, which can be ascribed to the formation of homogeneous thin films in combination with higher values of the open circuit voltage. Upon introduction of a higher amount of bromide (x = 0.33), the perovskite absorber layers form pinholes, thus reducing the overall device performance.
关键词： Semiconductors,Solar cell,Material science,Lead-free perovskite
更新于2025-09-19 17:13:59
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Conjugated Organic Cations Enable Efficient Self-Healing FASnI3 Solar Cells
摘要： The introduction of large-volume amines (LVAs) in Sn-based perovskite films has been shown to lead to promising power conversion efficiency (PCE) in Pb-free perovskite solar cells (PSCs). However, the LVAs adopted so far (e.g., phenylethylammonium [PEA] and butylammonium [BA]) are insulating and could impede charge extraction within the perovskite film. Herein, a conjugated LVA, 3-phenyl-2-propen-1-amine (PPA), is introduced in formamidinium tin iodide (FASnI3) perovskite. Our results show that the incorporation of PPA results in enlarged grain sizes, reduced trap density, preferential orientation, efficient charge extraction, and enhanced structural stability of FASnI3 film. These positive effects help in achieving efficient PSCs with a PCE as high as 9.61% with negligible hysteresis and outstanding stability (remains 92% of its initial PCE value after 1,440 h). Furthermore, the presence of PPA enables a self-healing action of PSCs. Most importantly, we report large-area (1 × 1 cm2) Sn-based PSCs achieving PCE of 7.08%.
关键词： FASnI3 solar cells,Lead-free perovskite,Photovoltaic performance,Self-healing,Conjugated organic cations
更新于2025-09-19 17:13:59