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Evolving antiferroelectric stability and phase transition behavior in NaNbO3-BaZrO3-CaZrO3 lead-free ceramics
摘要： The stability of antiferroelectricity in NaNbO3 ceramics was found to evolve with co-doping x mol% CaZrO3 and 6 mol% BaZrO3, from a dominant ferroelectric (FE) orthorhombic Q phase (x=0) to a gradually stabilized antiferroelectric (AFE) orthorhombic P phase owing to different ionic radii of Ba and Ca ions. Although a complete AFE P phase appears at x=0.5, the field induced AFE-FE phase transformation is irreversible at first, and then becomes partially reversible at x=1 and finally completely reversible at x=3. The above-mentioned change process proves to be associated with the enhancing stability of antiferroelectricity with x, as evidenced by means of dielectric, polarization and strain properties as well as in/ex-situ synchrotron x-ray diffraction and Raman spectra. A composition-field phase diagram for the NN-based lead-free AFE ceramic was constructed on basis of the phase structural change, which would provide a clear understanding of how ion doping influences its antiferroelectricity.
关键词： lead-free ceramics,Antiferroelectricity,phase transition,NaNbO3
更新于2025-11-14 17:28:48
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Luminescence and electrical properties of Eu-modified Bi <sub/>0.5</sub> Na <sub/>0.5</sub> TiO <sub/>3</sub> multifunctional Ceramics
摘要： The Eu3+ modified Bi0.5Na0.5TiO3 (BNT) ceramics have been fabricated by the solid-state reaction method. The impact of Eu3+ doping on the structure, photoluminescence and electrical properties has been studied by XRD, SEM, PL spectra and LCR meter. X-ray diffraction analysis reveals that the crystal structure of the samples is well matched with the trigonal perovskite, and the optimal temperature of pre-sintering is 880°C. The Eu3+ doped BNT ceramics show excellent red fluorescence at 614nm corresponding to the 5D0→7F2 transition of Eu3+ under 466nm excitation and relatively long fluorescence lifetime. The BNT-0.02Eu ceramic density is up to 5.68g/cm3 and the relative density is up to 94.6% with sintering temperature 1075°C. The piezoelectric constant (d33) of samples has been significantly improved up to 110pC/N by Eu3+ doping. The BNT-0.03Eu ceramic pre-sintered at 880°C and sintered at 1050°C has good dielectric properties and excellent luminescence properties. Eu3+ doped BNT ceramics make it potential applications for novel integrated optical-electro and multifunctional devices.
关键词： luminescence,electrical properties,Bismuth sodium titanate (Bi0.5Na0.5TiO3),lead-free ceramics
更新于2025-11-14 17:28:48
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Enhanced breakdown strength and energy storage density in a new BiFeO3-based ternary lead-free relaxor ferroelectric ceramic
摘要： A new ternary lead-free relaxor ferroelectric ceramic of (0.67-x)BiFeO3-0.33(Ba0.8Sr0.2)TiO3-xLa(Mg2/3Nb1/3)O3+y wt.% MnO2+z wt.% BaCu(B2O5) (BF-BST-xLMN+y wt.% MnO2+z wt.% BCB) was prepared by a solid-state reaction method. The substitution of LMN for BF was believed to induce a typical dielectric relaxation behavior owing to the increased random fields. After co-doping MnO2 and BCB, a significant decrease in the conductivity and grain size was simultaneously realized, resulting in obviously enhanced dielectric breakdown strength and energy-storage performances at room temperature. A high recoverable energy storage density W~3.38 J/cm3 and an acceptable energy storage efficiency η~59% were achieved in the composition with x=0.06, y=0.1 and z=2 under a measuring electric field of 23 kV/mm. In addition, the energy-storage performance is quite stable against both frequency (0.1 Hz-100 Hz) and temperature (30-170 oC), suggesting that BF-BST-xLMN+y wt.% MnO2+z wt.% BCB lead-free relaxor ferroelectric ceramics might be a promising dielectric material for high-power pulsed capacitors.
关键词： Lead-free ceramics,Relaxor ferroelectrics,Energy storage,BiFeO3,BDS
更新于2025-11-14 17:28:48
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Large electric field-induced strain in ternary Bi0.5Na0.5TiO3-BaTiO3-Sr2MnSbO6 lead-free ceramics
摘要： The large electric-field-induced strain of Bi0.5Na0.5TiO3-BaTiO3 based ceramic make it a potential replacement for lead-based ferroelectrics in actuator applications. Herein, a ternary system (1-x)(Bi0.5Na0.5)0.935Ba0.065TiO3-xSr2MnSbO6 (BNBT6.5-xSMS) ceramic was fabricated using conventional solid-state reaction. It was found that the ferroelectric to relaxor phase transition temperature TF-R gradually shifted to lower temperature by increasing SMS contents. The ferroelectricity and piezoelectricity of BNBT6.5 were highly affected by trace amount of SMS doping. For composition BNBT6.5-0.003SMS, where TF-R was near room temperature, a large electric-field-induced unipolar strain of ~0.4% with high normalized strain (Smax/Emax) of 728 pm/V, which is comparable to lead-based ferroelectric/antiferroelectric ceramics, was achieved owing to the reversible electric-field-induced phase transition between a non-polar relaxor phase to a polar phase with long-range ferroelectric order.
关键词： electric-field-induced phase transition,ferroelectric,Lead-free ceramics,Bi0.5Na0.5TiO3
更新于2025-09-23 15:23:52
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The sintering behavior and physical properties of Li <sub/>2</sub> CO <sub/>3</sub> -doped Bi <sub/>0.5</sub> (Na <sub/>0.8</sub> K <sub/>0.2</sub> ) <sub/>0.5</sub> TiO <sub/>3</sub> lead-free ceramics
摘要： In this study, Li2CO3-doped Bi0.5(Na0.8K0.2)0.5TiO3 (BNKT) ceramics were fabricated via the conventional solid-state reaction using ultrasound waves for preliminary milling. The milling time was shortened from 20 h to 1 h with ball milling. The phase structure of BNKT investigated by X-ray diffraction showed a single perovskite phase. With increasing Li2CO3 content, the phase structure of the ceramics changed from rhombohedral to tetragonal. At a sintering temperature of 1 100 8C and Li2CO3 content of 0.4 wt.%, the best physical properties of the ceramics, such as density (q), 5.9 g cm–3; electromechanical coupling factors (kp), 0.32; (kt), 0.29; remanent polarization (Pr), 12.0 lC cm–2; dielectric constant (er), 1 191; and highest dielectric constant (emax), 5 800, were obtained.
关键词： Lead-free ceramics,Electromechanical coupling factor,BNKT,Sintering temperature,Dielectric constant
更新于2025-09-23 15:23:52
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Effect of processing conditions on (Ba1-xCax)(Ti0.9Sn0.1)O3 lead-free ceramics for the enhancement of structural, humidity sensing and dielectric properties
摘要： The present study reports detailed guidelines for the preparation of high-quality perovskite (Ba1-xCax)(Ti0.9Sn0.1)O3 (BCTS) (x = 0.0–0.1) lead-free ceramics by solid state reaction. The compositions (x = 0.0–0.04) exhibit orthorhombic–tetragonal phase transition (TO-T), except x ≥ 0.06 that shows a pure tetragonal structure phase which conformed by X-ray diffraction (XRD). The microstructure and purity of the sintered ceramics were examined using scanning electron microscope equipped with an energy dispersive spectrometer (SEM-EDS). Some pores existing in the grain boundary were observed at high concentrations of Ca content. Field emission scanning electron microscope (FE-SEM) was used to examine the morphology of sensing film of the calcined powder and it was prepared as a humidity sensor using screen-printing technique. All the compositions exhibited poor sensitivity toward the humidity sensing in the range of 0–98% RH at room temperature. Hot-stage microscope (HSM) has been used to investigate the sintering curve of the pure calcined powder and it was found that the suitable sintering temperature for obtaining a fully dense microstructure is 1400 °C. The highest values of permittivity (εr = 46,515, at 10 kHz) and piezoelectric coefficient (d33 = 510 pC/N) were achieved in the composition x = 0.02. The difference between alumina and platinum crucibles for the processing of the powders has been introduced, and by the aid of dispersive spectrometer analysis and it was indicated that use of alumina crucibles leads to the undesired presence of Al in the ceramics, which can be prevented by using a capped platinum crucibles.
关键词： Lead-free ceramics,Humidity sensing,Phase formation,Processing,Dielectric properties
更新于2025-09-23 15:23:52
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Lead-free Ag <sub/> 1-3 <i>x</i> </sub> La <sub/><i>x</i> </sub> NbO <sub/>3</sub> Antiferroelectric Ceramics with High Energy Storage Density and Efficiency
摘要： Environmentally benign lead-free bulk ceramics with high recoverable energy density (Wrec) are very attractive in advanced pulsed power capacitors. In this work, composition engineering was adopted by La3+ modification to improve the energy storage performance of Ag1-3xLaxNbO3 ceramics. It was found the antiferroelectric (AFE) phase was stabilized after La3+ substitution, as a result of the reduced tolerance factor t. Significant improvement of Wrec and energy storage efficiency (η) were achieved with value of 3.12 J/cm3 and 0.63 for x=0.02 at an electric field of 230 kV/cm, more than 1.5 times the value of pure AgNbO3 (Wrec=1.9 J/cm3, η=0.40). The excellent energy storage properties are resulted from the increased antiferroelectric-ferroelectric phase transition electric field (EF), ferroelectric-antiferroelectric phase transition electric field (EA) and breakdown electric field (Eb). The enhanced Eb was ascribed to the decreased grain size and increased electrical resistivity upon La3+ modification. The feature makes Ag1-3xLaxNbO3 a potential candidate for energy storage applications.
关键词： energy storage,ferroelectricity/ferroelectric materials,lead-free ceramics,dielectric materials/properties
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE International Ultrasonics Symposium (IUS) - Kobe, Japan (2018.10.22-2018.10.25)] 2018 IEEE International Ultrasonics Symposium (IUS) - Lead-Free Sodium Potassium Niobate Based Piezoelectric Thick Film Bimorph Structure for Energy Harvesting
摘要： A novel piezoelectric ceramic-based bimorph energy harvester (PEH) is proposed in this paper for scavenging energy from low-frequency vibrations in many types of applications, such as in the human body or in industry. The PEH is based on a lead-free piezoelectric ceramic material (NKN-based) and is designed to operate efficiently at frequencies below 100 Hz. Experimental results show that the device can generate a power density of up to 22 μW/cm3 under an acceleration of 1 g at 20 Hz, which is highly competitive with existing energy harvesters. This work demonstrates the potential of using lead-free materials for sustainable energy harvesting technologies.
关键词： piezoelectric energy harvesting,NKN-based materials,low-frequency vibrations,lead-free ceramics,bimorph structure
更新于2025-09-23 15:22:29
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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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Outstanding piezoelectric properties, phase transitions and domain configurations of 0.963(K0.48Na0.52)(Nb0.955Sb0.045)O3?0.037(Bi0.50Na0.50)HfO3 ceramics
摘要： Requirements for substituting the current lead-based piezoelectric materials with lead-free ones are becoming increasingly strong from environmental concerns. In this article, we report piezoelectric properties, phase transitions and domain configurations of a dense 0.963(K0.48Na0.52)(Nb0.955Sb0.045)O3?0.037(Bi0.50Na0.50)HfO3 lead-free ceramic prepared through solid-state reaction by two-step sintering. It has a large piezoelectric coefficient d33 = 512 pC/N and a planner eletromechanical coupling coefficient kp ≈ 0.54 at room temperature. Dielectric measurement indicates that rhombohedral-orthorhombic, orthorhombic-tetragonal, and tetragonal-cubic phase transitions upon heating process occur at ?30 °C, 57 °C and 238 °C, respectively. X-ray diffraction analysis shows that the crystalline structure is dominantly of orthorhombic phase at room temperature. Domain configurations were investigated by acid etching technique. The poled ceramic shows domain patterns of long parallel stripes with hierarchical nanodomain structure existing in some broad stripes. The observed outstanding piezoelectric properties are ascribed to the rhombohedral-orthorhombic and orthorhombic-tetragonal phase transitions, and to the characteristic domain structure.
关键词： Phase transitions,Piezoelectricity,Lead-free ceramics,Ceramics,Ferroelectrics,Domain structure
更新于2025-09-10 09:29:36