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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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Reversible luminescence modulation and temperature sensing properties of Pr <sup>3+</sup> /Yb <sup>3+</sup> codoped K <sub/>0.5</sub> Na <sub/>0.5</sub> NbO <sub/>3</sub> ceramics
摘要： In this work, we have prepared a novel (K0.5Na0.5)0.99-xPrxYb0.01NbO3 (abbreviated as KNN:xPr3+/0.01Yb3+, x=0.0006, 0.0008, 0.001, 0.002, 0.003 and 0.004) ceramic, which possess visible UC emissions, photochromic (PC) and optical thermometric properties. Under the excitation of a 980-nm diode laser, all the samples show the featured emissions of Pr3+ ions and the UC emission intensity is greatly dependent on the Pr3+ doping content. The optimal UC luminescence intensity is obtained at x=0.001. All the prepared samples show a strong PC reaction, and a large luminescence quenching degree (ΔRt) of 74.94% is found. The optical thermometric properties of both the irradiated and unirradiated KNN:0.001Pr3+/0.01Yb3+ ceramics in the temperature range of 123-573 K have been investigated via measuring the temperature-dependent UC emission spectra of green emissions, which originate from the two 3P1 and 3P0 thermally coupled levels. It has been found that the prepared samples have both excellent PC behaviors and temperature sensing performances. These results suggest that the KNN:xPr3+/0.01Yb3+ ceramics are promising candidates for the applications in PC reaction and thermometers.
关键词： Ferroelectrics,Thermometer,Upconversion,Rare-earth ions,Photochromism
更新于2025-11-14 15:28:36
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Polarization and acoustic properties of barium-modified lead-free potassium–sodium niobate ceramics
摘要： Results of polarization and polarization switching in samples prepared by solid phase synthesis of the (1-х)(K0.5Na0.5)(Nb0.93Sb0.07)O3–xBaTiO3 + 0.5mol%MnO2 system at x = 0.01, 0.02, and 0.04 (KNNS7–xBT) studied over a wide range of temperatures are reported. The observed features of the dielectric nonlinearity at the ferroelectric and structural phase transitions in the materials are described. The dielectric response data of the samples of different contents of the admixture in the KNNS7–xВT ceramics are compared with the behaviour of their elastic properties.
关键词： dielectric permittivity,polarization,solid solutions,elastic properties,relaxors,ferroelectrics,ceramics
更新于2025-09-23 15:23:52
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Inkjet-printed silver as alternative top electrode for lead zirconate titanate thin films
摘要： In the present work, we describe direct patterning of silver top electrodes on polycrystalline Pb(Zr0.53Ti0.47)O3 (PZT) thin films via inkjet printing. The films were first deposited on platinized silicon via chemical solution deposition. Individual nanosilver ink droplets were then printed on the PZT surface to create round top electrodes with tunable diameter from 75 to 93 mm. Printing parameters and strategy were optimized for deposition of homogeneous electrodes. High quality of the printed silver electrodes sintered at 350 °C is confirmed via measurements of the direct piezoelectric response and polarization loops of PZT thin films, whose results are comparable to the ones obtained for sputtered platinum top electrodes, with e31,f = -4.1 C m-2 and Ec ~55 kV cm-1, Pr ~20 mC cm-2.
关键词： Piezoelectricity,Thin films,Silver electrodes,Inkjet printing,Ferroelectrics
更新于2025-09-23 15:23:52
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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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On the mechanisms of tip-force induced switching in ferroelectric thin films: The crossover of depolarization, shear strain and flexoelectricity
摘要： The recent observation of mechanical switching of ferroelectric polarization has placed the mechanical manipulation of ferroelectrics on an equal footing with the conventional electrical manipulation. However, discussions on the exact switching mechanisms due to mechanical loads are ongoing for the complexity in experimental situations. In this work, based on continuum mechanical and thermodynamic modeling and simulation, we analyze the mechanisms of tip-force induced switching in ferroelectric thin films. The roles of depolarization, shear strain and flexoelectricity in mechanical switching, both in normal and sliding loading modes, are separated out and the switching characteristics are analyzed. The depolarization field in the film is demonstrated to enable bidirectional switching. The coupling between shear strain and polarization components is shown to be important in the sliding loading mode. A great influence of flexoelectricity-modified polarization boundary condition on the switching process is revealed. The previous speculation that the switching process experiences an intermediate paraelectric phase is proved. The regulation of loading force, misfit strain, temperature and film thickness on the switching are further given for each mechanism. Taking all of the three mechanisms into account, we present the phase diagrams of mechanical switching for films in an initial upward or downward polarization state. The revealed characteristics of various switching mechanisms should provide useful guidelines for their verification in experiments, and the tunability of the switching by various influencing factors is instructive for the design and optimization of ferroelectric devices via mechanical engineering.
关键词： shear strain,mechanical switching,ferroelectrics,flexoelectricity,depolarization
更新于2025-09-23 15:23:52
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Enabling PIEZOpotential in PIEZOelectric Semiconductors for Enhanced Catalytic Activities
摘要： The past several decades have witnessed significant advances in synthesis and applications of PIEZOelectric semiconductors. They represent an important class of materials, including ferroelectric semiconductors. Notably, an intriguing combination of physical and chemical phenomena in PIEZOelectric semiconductors has triggered much interest in PIEZOcatalysis. Regardless of a short period of time for the development of PIEZOcatalysis, remarkable progress has been made in this field. Herein, this review summarizes recent development in PIEZOcatalysis enabled by PIEZOelectric semiconductors due to PIEZOpotential (i.e., piezopotential, pyropotential, and ferropotential)-induced built-in electric field. First, the PIEZOelectrics (i.e., piezoelectrics, pyroelectrics and ferroelectrics) are briefly introduced. Second, recent developments pertaining to PIEZOpotential-mediated catalysis are highlighted, including the introduction of representative PIEZOelectric semiconductors, their possible catalytic mechanisms, novel PIEZOelectric effects during catalytic process, and several appealing examples about PIEZOcatalysis. Finally, the challenges in the field and exciting opportunities to further improve the PIEZOcatalytic efficiency are discussed.
关键词： Ferroelectrics,Catalysis,Piezoelectrics,Pyroelectrics
更新于2025-09-23 15:23:52
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Effect of an electric field on the electrocaloric response of ferroelectrics
摘要： The electrocaloric effect of the model ferroelectric BaTiO3 was investigated using phenomenological theory. The results indicate that the applied electric field strength is a key factor for the induced electrocaloric response and there are two distinguishing electrocaloric responses. When a moderate electric field is applied, the electrocaloric temperature variation is small but the electrocaloric strength is high. In contrast, the electrocaloric temperature variation is large but electrocaloric strength is low when a very high electric field is applied. These results are consistent with the experimental observations on BaTiO3 based bulk and thin film ferroelectric materials.
关键词： BaTiO3,ferroelectrics,electrocaloric effect
更新于2025-09-23 15:23:52
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[IEEE 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Austin, TX, USA (2018.9.24-2018.9.26)] 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Biaxial Strain based Performance Modulation of Negative-Capacitance FETs
摘要： In this work, we report device simulations conducted to study the performance of biaxially strained ferroelectric-based negative capacitance FETs (NCFETs). We adopted PbZr0.5Ti0.5O3 (PZT) and HfO2 as ferroelectric materials and applied biaxial strain using the first-principles method. It was found that PZT and HfO2 show different trends in the negative capacitance (NC) region under biaxial strain. Biaxial strain strongly affects the NC of PZT, whereas HfO2 is not as susceptible to biaxial strain as PZT. When no strain is applied, HfO2-based NCFETs exhibit a better performance than PZT-based NCFETs. However, the subthreshold slope and ON-state current are improved in the case of PZT-based NCFETs when the compressive biaxial strain is increased, whereas the performance of HfO2-based NCFETs is slightly degraded. In particular, the negative drain-induced barrier lowering and negative differential resistance vary considerably when compressive strain is applied to PZT-based NCFETs.
关键词： strain,negative capacitance FETs,ferroelectrics,density functional theory,HfO2,PZT
更新于2025-09-23 15:22:29