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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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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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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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A method for determining the orientation of [011] poled relaxor ferroelectric single crystal disks
摘要： A new method for determining the crystal orientation of [011] poled relaxor ferroelectric single crystal (RFSC) disks has been developed. This Technical Note describes the measurement techniques and mathematical approaches associated with this new method, which is possible due to the anisotropic response of [011] poled single crystal disks. Experimentally, the disks are subject to a distributed edge load at a series of angular orientations, with the output voltage recorded at each orientation. Equations have been developed to govern a particle swarm to find an optimised fit to the experimental data yielding the crystal orientation of the disk which is required for practical applications. Approximate values for the piezoelectric charge constants d31, d32 are also determined. The method is demonstrated on a RFSC Mn-PMN-PZ-PT disk, comparing favourably with a synchrotron x-ray transmission diffraction study on the same disk.
关键词： particle swarm,piezoelectric charge constant,crystal orientation,single crystal,relaxor ferroelectrics
更新于2025-09-19 17:13:59
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Photoluminescence and ferroelectric behaviors related to Sr/Ba ratio in Eu3+ doped (Sr Ba1-)0.98Eu0.02Nb2O6 multifunctional tungsten bronze ceramics
摘要： The lead-free Eu3+ doped (SrxBa1-x)0.98Eu0.02Nb2O6 (SBEN, 0.3 (cid:2) x (cid:2) 07) ceramics were fabricated by conventional solid-state reaction method. Eu3+ was chosen as a dopant with the goal of inducing strong red-emitting photoluminescence based on their electrical properties. Effects of Sr/Ba ratio on the crystal structure, dielectric, ferroelectric and photoluminescent properties of SBEN ceramics were investigated by changing x. Single tungsten bronze structure with P4bm space group was obtained for all ceramics. The ceramics grain morphology varied obviously from homogenous equiaxed shape to anisometric pillar-type shape with increasing x. According to the dielectric spectra, the obtained SBEN ceramics transited from normal ferroelectrics to relaxor ferroelectrics, accompanied by the gradual decrease of Tm with increasing Sr2+ amount in A-sites. Two strong emitting peaks corresponding to the orange magnetic dipole transitions (594 nm, 5D0/7F1) and red electric dipole transitions (618 nm, 5D0/7F2) were obtained for all SBEN ceramics. The red/orange-emitting ratio of Eu3+ related to the Sr/Ba ratio in the composition was studied in this work to discuss the ions occupying situation in different A-sites.
关键词： Relaxor ferroelectrics,Dielectric properties,Luminescence,Tungsten bronze structure
更新于2025-09-10 09:29:36
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Crystal structure and electrical properties of textured Ba2Bi4Ti5O18 ceramics
摘要： Highly textured Ba2Bi4Ti5O18 ceramic was prepared by spark plasma sintering (SPS). X-ray di?raction of the ceramics revealed the coexistence of a major ferroelectric phase (Space group, SG: B2cb) and a minor paraelectric phase (SG: I4/mmm) at room temperature. A di?used phase transition was observed at around 240 °C. The evolution of the switching current peaks in the electric current vs. electric ?eld (I-E) loops with increasing temperature was interpreted by the structural changes and temperature dependent polarisation reversal processes. The slim polarisation vs. electric ?eld (P-E) loops, the extra switching current peaks in the I-E loops and the non-zero piezoelectric d33 coe?cient indicate that Ba2Bi4Ti5O18 is a relaxor ferroelectric material. The recoverable energy density (0.41 ± 0.01 J/cm3) of Ba2Bi4Ti5O18 ceramics in the perpendicular direction to the SPS pressing direction is close to that of Pb(Mg1/3Nb2/3)O3-based ceramics. The obtained results suggest Ba2Bi4Ti5O18 ceramics might be promising for energy storage applications.
关键词： Ba2Bi4Ti5O18,Texture,Relaxor ferroelectrics,Energy storage,Bismuth layer-structured ferroelectrics
更新于2025-09-04 15:30:14