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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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Significantly enhanced room temperature electrocaloric response with superior thermal stability in sodium niobate-based bulk ceramics
摘要： Converting electrical into thermal energy in ferroelectrics path the way for a novel cooling technology, be able to open up new fields of applications. For electrocaloric refrigeration, large temperature change (ΔT) and excellent temperature stability are highly desired. Unfortunately, a large room temperature ΔT in lead free bulk ceramics was usually obtained at the expense of temperature stability, and vice versa, limiting their practical applications. In this work, composition engineering is carried out as an important strategy to tune phase transition to room temperature and simultaneously induce diffuse phase transition to achieve excellent temperature stability. A large room temperature ΔT is realized by the application of large electric fields, possibly due to the optimization of the sintering process in sodium niobate based ceramics. The 0.78NaNbO3-0.22BaTiO3 ceramic is found to exhibit both large room temperature ΔT (~ 0.70 K) and superior temperature stability (±1.4% variation in ΔT from 300 K to 380 K). Those properties are superior to previously reported lead-free bulk ceramics. This work provides a guideline for the development of high-performance ceramic materials such as NaNbO3-ABO3 (A=Ba, Sr and Ca; and B=Ti and Zr) for electrocaloric refrigeration. Most importantly, this work expands the applications of NN-based ceramics from electric energy storage, electrostrictive and piezoelectric applications, to a new field, i.e. solid-state refrigeration. This makes NN-based ceramics very promising multifunctional materials for device integration.
关键词： Sodium niobate,relaxor ferroelectrics,electrocaloric effect,adiabatic temperature change,diffuse phase transitions
更新于2025-11-14 17:28:48
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(Bi0.51 Na0.47)TiO3 based lead free ceramics with high energy density and efficiency
摘要： Dielectric ceramics with high energy storage density and energy efficiency play an important role in high power energy storage applications. In this work, lead free relaxor ferroelectric ceramics in (1-x)Bi0.51Na0.47TiO3-xBa(Zr0.3Ti0.7)O3 (BNT-BZT100x: x=0.20, 0.30, 0.40 and 0.50) system are fabricated by conventional solid-state sintering method. The BNT-BZT100x ceramics are sintered dense with minimal pores, exhibiting pseudocubic symmetry and strong relaxor characteristic. A very high energy storage density of 3.1 J/cm3 and high energy efficiency of 91% are simultaneously achieved in BNT-BZT40 ceramic with 0.1mm in thickness, at the applied electric field of 280 kV/cm. The temperature stability of the energy density is studied over temperature range of 20-160°C, showing minimal variation below 1.5%, together with the excellent cycling reliability (the variations of both energy density and efficiency are below 3% up to 106 cycles), making BNT-BZT40 ceramic promising as a candidate for high-temperature dielectric and energy storage applications.
关键词： relaxor characteristic,lead free ceramic,energy storage
更新于2025-11-14 17:28:48
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High electromechanical strain properties in SrTiO3?modified Bi1/2Na1/2TiO3?KTaO3 lead?free piezoelectric ceramics under low electric field
摘要： This study investigated the structures, dielectric, ferroelectric and piezoelectric properties of (0.99?x)Bi1/2Na1/2TiO3?0.01KTaO3?xSrTiO3 (BNT?KT?100xST, x = 0.20 ~ 0.235) lead?free piezoelectric ceramics. These piezoceramics were synthesized by conventional solid?state reaction method. As a consequence, a large electrical strain and normalized strain (d33* ≈ 793 pm/V) can be obtained even under 3 kV/mm as low electric field for BNT?KT?22.5ST ceramics. The phase transition between nonergodic relaxor (NER) and ergodic relaxor (ER) under electric field might be responsible for its large strain. It means that BNT?KT?100xST lead?free ceramics can be a promising candidate for actuator applications.
关键词： Phase transition,Lead-free,Ternary system,Piezoelectric ceramics,Relaxor
更新于2025-11-14 17:28:48
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Phase-transition induced giant negative electrocaloric effect in a lead-free relaxor ferroelectric thin film
摘要： Ferroelectric/antiferroelectric thin/thick films with large positive or negative electrocaloric (EC) effects could be very useful in designing commercial refrigeration devices. Here, a giant negative EC effect (maximum ΔT ≈ ?42.5 K with ΔS ≈ ?29.3 J K?1 kg?1) comparable to the best positive EC effects reported so far is demonstrated for 0.5(Ba0.8Ca0.2)TiO3–0.5Bi(Mg0.5Ti0.5)O3 (BCT–BMT) lead-free relaxor ferroelectric thin films prepared on Pt(111)/TiOx/SiO2/Si substrates using a sol–gel method. An electric-field induced structural phase transition (nanoscale tetragonal and orthorhombic to rhombohedral) along the out-of-plane [111] direction plays a very key role in developing the giant negative EC effect. This breakthrough will pave the way for practical applications of next-generation refrigeration devices with high cooling efficiency in one cycle by ingeniously utilizing and combining both the giant negative and positive EC effects. Moreover, a large energy density of 51.7 J cm?3 with a high power density of 1.15 × 1010 W kg?1 at room temperature is also achieved in the thin film, indicating that it is also an attractive multifunctional material for energy storage.
关键词： lead-free,energy storage,electrocaloric effect,phase transition,thin film,relaxor ferroelectric
更新于2025-11-14 17:28:48
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Detecting the Burns temperature in Na <sub/>0.5</sub> Bi <sub/>0.5</sub> TiO <sub/>3</sub> -xBaTiO <sub/>3</sub> lead-free relaxor ferroelectrics by means of acoustic emission
摘要： Na0.5Bi0.5TiO3-xBaTiO3 ceramics samples (0 < x < 0.8) were studied by means of an acoustic emission method. The characteristic temperatures such as the Burns temperature, TB, the transition to paraelectric phase, Tp, the temperature maximum of the dielectric constant, Tm, and the intermediate temperature, T ? were detected and their dependences on x were plotted. Based on the comparison of the obtained data with the previously published ones, it is shown that the Burns temperature, TB, cannot be reliably determined by the deviation of the reverse dielectric constant, 1/ε(cid:3), from a straight line.
关键词： phase transitions,relaxor ferroelectrics,Na0.5Bi0.5TiO3-xBaTiO3,Burns temperature,acoustic emission
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Budapest (2018.7.1-2018.7.5)] 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Influence of Composition and Preparation on Crystalline Phases and Morphology in Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) Relaxor-Ferroelectric Terpolymer
摘要： The influence of chemical composition and crystallisation conditions on the ferroelectric and paraelectric phases and the resulting morphology in Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) terpolymer films with 55.4/37.2/7.3 mol% or with 62.2/29.4/8.4 mol% of VDF/TrFE/CFE was studied. Poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) with 75/25 mol% VDF/TrFE was employed as reference material. Fourier-Transform Infrared Spectroscopy (FTIR) was used to determine the fractions of the relevant terpolymer phases, and X-Ray Diffraction (XRD) was employed to assess the crystalline morphology. The FTIR results show an increase of the fraction of paraelectric phases after annealing. On the other hand, XRD results indicate a more stable paraelectric phase in the terpolymer with higher CFE content.
关键词： P(VDF-TrFE-CFE) terpolymer,Curie transition,relaxor-ferroelectric polymer,ferroelectric and paraelectric phases
更新于2025-09-23 15:22:29
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Decoupling mesoscale functional response in PLZT across the ferroelectric – relaxor phase transition with contact Kelvin probe force microscopy and machine learning
摘要： Relaxor ferroelectrics exhibit a range of interesting material behavior including high electromechanical response, polarization rotations as well as temperature and electric field-driven phase transitions. The origin of this unusual functional behavior remains elusive due to limited knowledge on polarization dynamics at the nanoscale. Piezoresponse force microscopy and associated switching spectroscopy provide access to local electromechanical properties on the micro- and nanoscale, which can help to address some of these gaps in our knowledge. However, these techniques are inherently prone to artefacts caused by signal contributions emanating from electrostatic interactions between tip and sample. Understanding functional behavior of complex, disordered systems like relaxor materials with unknown electromechanical properties therefore requires a technique that allows to distinguish between electromechanical and electrostatic response. Here, contact Kelvin probe force microscopy (cKPFM) is used to gain insight into the evolution of local electromechanical and capacitive properties of a representative relaxor material lead lanthanum zirconate across the phase transition from a ferroelectric to relaxor state. The obtained multidimensional data set was processed using an unsupervised machine learning algorithm to detect variations in functional response across the probed area and temperature range. Further analysis showed formation of two separate cKPFM response bands below 50°C, providing evidence for polarization switching. At higher temperatures only one band is observed, indicating an electrostatic origin of the measured response. In addition, from the cKPFM data qualitatively extracted junction potential difference, becomes independent of the temperature in the relaxor state. The combination of this multidimensional voltage spectroscopy technique and machine learning allows to identify the origin of the measured functional response and to decouple ferroelectric from electrostatic phenomena necessary to understand the functional behavior of complex, disordered systems like relaxor materials.
关键词： phase transition,machine learning,Relaxor ferroelectric,lead lanthanum zirconium titanate,piezoresponse force microscopy,k-means clustering,contact Kelvin probe force microscopy
更新于2025-09-23 15:21:01
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Relaxor Behavior in Ordered Lead Magnesium Niobate (PbMg <sub/>1/3</sub> Nb <sub/>2/3</sub> O <sub/>3</sub> ) Thin Films
摘要： The local compositional heterogeneity associated with the short-range ordering of Mg and Nb in PbMg1/3Nb2/3O3 (PMN) is correlated with its characteristic relaxor ferroelectric behavior. Fully ordered PMN is not prepared as a bulk material. This work examines the relaxor behavior in PMN thin films grown at temperatures below 1073 K by artificially reducing the degree of disorder via synthesis of heterostructures with alternate layers of Pb(Mg2/3Nb1/3)O3 and PbNbO3, as suggested by the random-site model. 100 nm thick, phase-pure films are grown epitaxially on (111) SrTiO3 substrates using alternate target timed pulsed-laser deposition of Pb(Mg2/3Nb1/3)O3 and PbNbO3 targets with 20% excess Pb. Selected area electron diffraction confirms the emergence of (1/2, 1/2, 1/2) superlattice spots with randomly distributed ordered domains as large as ≈150 nm. These heterostructures exhibit a dielectric constant of 800, loss tangents of ≈0.03 and 2× remanent polarization of ≈11 μC cm?2 at room temperature. Polarization–electric field hysteresis loops, Rayleigh data, and optical second-harmonic generation measurements are consistent with the development of ferroelectric domains below 140 K. Temperature-dependent permittivity measurements demonstrate reduced frequency dispersion compared to short range ordered PMN films. This work suggests a continuum between normal and relaxor ferroelectric behavior in the engineered PMN thin films.
关键词： random site model,relaxor,ferroelectricity,short- and long-range order,temperature-dependent Rayleigh analysis
更新于2025-09-23 15:21:01
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Colossal dielectric, relaxor ferroelectric, diamagnetic and weak ferromagnetic properties of NdCrO3 perovskite nanoparticles
摘要： The NdCrO3 perovskite nanoparticles have been successfully synthesized using sol–gel auto-combustion process. Structural and morphological characterizations of the material have been performed at room temperature using XRD and SEM, respectively. Frequency- and temperature-dependent dielectric measurements have been performed in the range of 1 Hz–10 MHz and RT - 300 °C, respectively. The dielectric constant is found to be in the order of e0 > 103 at room temperature, indicating the colossal dielectric constant behaviour. Ferroelectric phase transition temperature has increased with an increase in frequency, suggesting that the material is a relaxor ferroelectric nature. Temperature- and field-dependent magnetization measurements have been carried out in the temperature range (5–400 K) and field up to 5 T. M–T curve exhibited a diamagnetic-like behaviour in low temperature and low fields. Two magnetic transitions were found at TN1 (223 K) and TN2 (33 K) which correspond to para to weak ferromagnetic transition and Nd3+ spin ordering, respectively. Hysteresis loop noticed weak ferromagnetism.
关键词： weak ferromagnetic properties,relaxor ferroelectric,Colossal dielectric,diamagnetic,NdCrO3 perovskite nanoparticles
更新于2025-09-23 15:19:57