Search Results (53)

For relaxor ferroelectric single crystal (1 − x)Pb(Mg_1/3Nb_2/3)O₃ − xPbTiO₃ (PMN-PT), through reasonable component regulation and electric field polarization, an orthogonal mm² point group structure can be obtained, which has high piezoelectric constants and is, therefore, a desired substrate material for lateral-field-excited (LFE) bulk acoustic wave (BAW) devices. In this work, acoustic wave resonance characteristics of (zxt) 45° PMN-PT BAW devices with LFE are investigated. Firstly, Mindlin first-order plate theory is used to obtain vibration governing equations of orthorhombic crystals excited by a lateral electric field. By analyzing the electrically forced vibrations of the finite plate, the basic vibration characteristics, such as motional capacitance, resonant frequency, and mode shape are obtained, and influences of different electrode parameters on resonance characteristics of the device are investigated. In addition, the effects of the structure parameters on the mass sensitivity of the devices are analyzed and further verified by FEM simulations. The model presented in this study can be conveniently used to optimize the structural parameters of LFE bulk acoustic wave devices based on orthorhombic crystals, which is crucial to obtain good resonance characteristics. The results provide an important basis for the design of LFE bulk acoustic wave resonators and sensors by using PMN-PT orthorhombic crystals. Full article

Relaxor ferroelectrics based on sodium bismuth titanate (Bi_0.5Na_0.5TiO₃, BNT) have attracted more interest recently as potential ecologically acceptable materials for pulse power technology because of their excellent full-energy storage capabilities. This paper formed (1 − x){0.97[0.98(BNT-ST)-0.02CN]-0.03AlN}-xNN ceramics through a traditional solid-state reaction process. It was noted that the incorporation of NaNbO₃ enhances the property of energy storage by elevating the breakdown strength and causing the creation of an ergodic relaxation state. The effective energy storage density (W_rec) and the energy storage efficiency (η) are 1.09 J/cm³ and 85%, respectively. The breakdown field strength E_b reached 155 kV/cm at x = 40%. These ceramics have excellent temperatures and frequency stabilities from 0.5 to 50 Hz and 20 to 60 °C. Full article

Dielectric capacitors with a high density of recoverable energy storage are extremely desirable for a variety of uses. However, these capacitors often exhibit lower breakdown strengths and energy efficiency compared to other materials, which poses significant challenges for their practical use. We report on a novel antiferroelectric ceramic system in the present study, (1 − x){0.97[0.985(0.93Bi_0.5Na_0.5TiO₃–0.07BaTiO₃)–0.015Er)]–0.03AlN}–xNaNbO₃ (x = 0, 10 wt%, 20 wt%, 30 wt%, and 40 wt%), synthesized via a conventional solid-state reaction approach. Here, (Bi_0.5Na_0.5TiO₃–BaTiO₃) is denoted as BNT–BT. We observed that varying the NaNbO₃ (NN) content gradually refined the grain size of the ceramics, narrowed their hysteresis loops, and transformed their phase structure from antiferroelectric to relaxor ferroelectric. These changes enhanced breakdown strength (E_b), thus increasing the performance of energy storage. Specifically, the recoverable energy density (W_rec) and energy storage efficiency (η), respectively, reached 0.67–1.06 J/cm³ and 44–88% at electric fields of 110–155 kV/cm, with the highest performance observed at 30 wt% NN doping. Additionally, over a broad range of temperature and frequency, the 70 wt% {0.97[0.985(BNT–BT)–0.015Er]–0.03AlN}–30 wt% NN ceramic demonstrated exceptional stability in energy storage. These results demonstrate the significant potential of lead-free(1 − x)({0.97[0.985(BNT–BT)–0.015Er]–0.03AlN}–xNN ceramics for the applications of high-performance energy storage. Full article

The influence of processing procedures and microstructural features on the functional properties of relaxor ferroelectric ceramics are of fundamental interest and directly relevant to their applications in dielectric capacitors and electromechanical sensors/actuators. In the present work, solid solutions of 0.65(K_0.5Bi_0.5)TiO₃-0.35(Ba_0.94Ca_0.06)(Ti_0.93Zr_0.07)O₃ (0.65KBT-0.35BCZT) were processed by solid-state reaction using two different procedures, distinguished in terms of mixed or separate calcination of the KBT and BCZT components and leading to homogeneous or core-shell-type relaxor ferroelectric ceramics, respectively. Systematic research was conducted on the impact of the processing techniques and air-quenching procedures on the structure and ferroelectric and electromechanical properties. Higher remanent polarization of the separately calcined materials was ascribed to the ferroelectric nature of the core regions, along with the non-ergodic relaxor ferroelectric response in the shell, which was enhanced by the quenching process. It was also demonstrated that the thermal depolarization temperature increased significantly after quenching, from ~100 to ~160 °C for the separately calcined ceramic, and from ~50 to ~130 °C for the mixed material; moreover, these effects are linked to notable improvements in the ferroelectric tetragonal phase content by air-quenching. Full article

Relaxor ferroelectric film capacitors exhibit high power density with ultra-fast charge and discharge rates, making them highly advantageous for consumer electronics and advanced pulse power supplies. The Aurivillius-phase bismuth layered ferroelectric films can effectively achieve a high breakdown electric field due to their unique insulating layer ((Bi₂O₂)²⁺ layer)). However, designing and fabricating Aurivillius-phase bismuth layer relaxor ferroelectric films with optimal energy storage characteristics is challenging due to their inherently stable ferroelectric properties. In this work, lead-free CaBi_4-xLa_xTi₄O₁₅ films were synthesized using the sol–gel technique and a weakly coupled relaxor design. On one hand, the introduction of La³⁺ ions weaken the dipole–dipole interactions, thereby enhancing the relaxor behavior. Alternatively, the expansion of grain size is restricted to enhance the number of grain boundaries, which possess improved insulating properties. This leads to a higher breakdown electric field. The results indicate that CaBi_4-xLa_xTi₄O₁₅ (x = 1.0) films exhibit excellent recoverable energy storage density (70 J/cm³) and high energy efficiency (73%). Moreover, the film exhibited good temperature stability and frequency stability. This study not only identifies a promising material for dielectric film capacitors but also demonstrates that the energy storage capabilities of Aurivillius-phase bismuth layer ferroelectric films can be effectively modulated through a design incorporating weakly coupled relaxor characteristics. Full article

Ceramic capacitors have received great attention for use in pulse power systems owing to their ultra-fast charge–discharge rate, good temperature stability, and excellent fatigue resistance. However, the low energy storage density and low breakdown strength (BDS) of ceramic capacitors limit the practical applications of energy storage technologies. In this work, we present a series of relaxor ferroelectric ceramics (1−x) [0.94 Bi_0.5Na_0.5TiO₃ –0.06BaTiO₃]– x Sr_0.7Bi_0.2TiO₃ (1-x BNT-BT- x SBT; x = 0, 0.20, 0.225, 0.25, 0.275 and 0.30) with improved energy storage performances by combining relaxor and antiferroelectric properties. XRD, Raman spectra, and SEM characterizations of BNT-BT-SBT ceramics revealed a rhombohedral–tetragonal phase, highly dynamic polar nanoregions, and a reduction in grain size with a homogeneous and dense microstructure, respectively. A high dielectric constant of 1654 at 1 kHz and low remnant polarization of 1.39 µC/cm² were obtained with the addition of SBT for x = 0.275; these are beneficial for improving energy storage performance. The diffuse phase transition of these ceramics displays relaxor behavior, which is improved with SBT and confirmed by modified the Curie–Weiss law. The combining relaxor and antiferroelectric properties with fine grain size by the incorporation of SBT enables an enhanced maximum polarization of a minimized P-E loop, leading to an improved BDS. As a result, a high recoverable energy density W_rec of 1.02 J/cm³ and a high energy efficiency η of 75.98% at 89 kV/cm were achieved for an optimum composition of 0.725 [0.94BNT-0.06BT]-0.275 SBT. These results demonstrate that BNT-based relaxor ferroelectric ceramics are good candidates for next-generation ceramic capacitors and offer a potential strategy for exploiting novel high-performance ceramic materials. Full article

The inevitable feedback between the environmental and energy crisis within the next decades can probably trigger and/or promote a global imbalance in both financial and public health terms. To handle this difficult situation, in the last decades, many different classes of materials have been recruited to assist in the management, production, and storage of so-called clean energy. Probably, ferromagnets, superconductors and ferroelectric/piezoelectric materials stand at the frontline of applications that relate to clean energy. For instance, ferromagnets are usually employed in wind turbines, superconductors are commonly used in storage facilities and ferroelectric/piezoelectric materials are employed for the harvesting of stray energy from the ambient environment. In this work, we focus on the wide family of ferroelectric/piezoelectric materials, reviewing their physical properties in close connection to their application in the field of clean energy. Among other compounds, we focus on the archetypal compound Pb(Zr,Ti)O₃ (or PZT), which is well studied and thus preferred for its reliable performance in applications. Also, we pay special attention to the advanced ferroelectric relaxor compound (1−x)Pb(Mg_1/3Nb_2/3)O₃−xPbTiO₃ (or PMN-xPT) due to its superior performance. The inhomogeneous composition that many kinds of such materials exhibit at the so-called morphotropic phase boundary is reviewed in connection to possible advantages that it may bring when applications are considered. Full article

Energy storage efficiency (η) and large recoverable energy density (W_re) are necessary for antiferroelectric materials in order to develop antiferroelectric-based dielectric capacitors with exceptional energy storage capacity. In the present paper, the effect of doping La³⁺ on the energy storage capacity of Pb_1−xLa_x(Hf_0.45Sn_0.55)_0.995O₃ antiferroelectric ceramics was studied. Adjusting the content of La and changing the phase structure of PLHS from antiferroelectric to relaxor ferroelectric gradually, which narrowed its hysteresis loop, yielded a high energy storage efficiency of 81.9% and the maximum breakdown field strength of 200 kV/cm when x = 2 mol%. In addition, the recoverable energy density and energy storage efficiency both showed excellent temperature stability and frequency stability in the temperature range of 10–110 °C and the frequency range of 10–100 Hz, suggesting that Pb_0.98La_0.02(Hf_0.45Sn_0.55)_0.995O₃ are favorable materials candidates for the preparation of pulsed-power capacitors that can be used in a wide range of conditions. Full article

With the intensification of the energy crisis, it is urgent to vigorously develop new environment-friendly energy storage materials. In this work, coexisting ferroelectric and relaxor-ferroelectric phases at a nanoscale were constructed in Sr(Zn_1/3Nb_2/3)O₃ (SZN)-modified (Bi_0.5Na_0.5)_0.94Ba_0.06TiO₃ (BNBT) ceramics, simultaneously contributing to large polarization and breakdown electric field and giving rise to a superior energy storage performance. Herein, a high recoverable energy density (W_rec) of 5.0 J/cm³ with a conversion efficiency of 82% at 370 kV/cm, a practical discharged energy density (W_d) of 1.74 J/cm³ at 230 kV/cm, a large power density (P_D) of 157.84 MW/cm³, and an ultrafast discharge speed (t_0.9) of 40 ns were achieved in the 0.85BNBT-0.15SZN ceramics characterized by the coexistence of a rhombohedral-tetragonal phase (ferroelectric state) and a pseudo-cubic phase (relaxor-ferroelectric state). Furthermore, the 0.85BNBT-0.15SZN ceramics also exhibited excellent temperature stability (25–120 °C) and cycling stability (10⁴ cycles) of their energy storage properties. These results demonstrate the great application potential of 0.85BNBT-0.15SZN ceramics in capacitive pulse energy storage devices. Full article

The (Na_0.5Bi_0.5)TiO₃ relaxor ferroelectric materials have great potential in high energy storage capacitors due to their small hysteresis, low remanent polarization and high breakdown electric field. In this work, (Na_0.5Bi_0.5)TiO₃ thin films with ~400 nm were prepared on (001) SrTiO₃ substrate by pulsed laser deposition technology. The (Na_0.5Bi_0.5)TiO₃ films have good crystallization quality with a dense microstructure and relaxor ferroelectric properties, as confirmed by the elongated hysteresis loops and the relation of <A>∝E^α. A high E_b of up to 1400 kV/cm is obtained, which contributes to a good W_rec of 24.6 J/cm³ and η of 72% in (Na_0.5Bi_0.5)TiO₃ film. In addition, the variations of W_rec and η are less than 4% and 10% in the temperature range of 20–120°C. In the frequency range of 10³ Hz–2 × 10⁴ Hz, the variations of W_rec and η are less than 10%. All those reveal the great potential of NBT film for energy storage. Full article

BaTiO₃-Bi(Zn,Ti)O₃ (BT-BZT) ceramics have been used as capacitors due to their large dielectric permittivity and excellent temperature stability and are good candidates for lead-free materials for electrocaloric and energy storage devices. However, BT-BZT ceramics often suffer from inferior properties and poor reproducibility due to heterogeneous compositional distribution after calcination and sintering. In this work, (1−x)BT-xBZT ceramics (x = 0~0.2) were fabricated with nano-sized BaTiO₃ raw materials (nano-BT) by a solid-state reaction method to enhance the chemical homogeneity. The (1−x)BT-xBZT ceramics prepared from the nano-BT showed larger densities and more uniform microstructures at the lower calcination and sintering temperatures than the samples prepared from more frequently used micrometer-sized raw materials BaCO₃, TiO₂, Bi₂O₃, and ZnO. The (1−x)BT-xBZT ceramic prepared from the nano-BT displayed a phase transition from a tetragonal ferroelectric to a pseudo-cubic relaxor in a narrower composition range than the sample prepared from micro-sized raw materials. Larger adiabatic temperature changes due to the electro-caloric effect (ΔT_ECE) and recoverable energy storage density (U_rec) were observed in the samples prepared from the nano-BT due to the higher breakdown electric fields, the larger densities, and uniform microstructures. The 0.95BT-0.05BZT sample showed the largest ΔTECE of 1.59 K at 80 °C under an electric field of 16 kV/mm. The 0.82BT-0.18BZT sample displayed a U_rec of 1.45 J/cm², which is much larger than the previously reported value of 0.81 J/cm² in BT-BZT ceramics. The nano-BT starting material produced homogeneous BT-BZT ceramics with enhanced ECE and energy storage properties and is expected to manufacture other homogeneous solid solutions of BaTiO₃ and Bi-based perovskite with high performance. Full article

The versatile electrocaloric (EC) behaviors of the (1-x)Pb(Mg_1/3Nb_2/3)O₃-xPT (PMN-100xPT) single crystal are closely related to the multiple phase transitions under the multiple fields of electric field and temperature. In this work, the EC effect of <001>-oriented PMN-30PT single crystals with chemical composition at morphotropic phase boundary has been studied during the phase transformation process from the ferroelectric rhombohedral (R) phase to the tetragonal (T) phase. Two consecutive negative EC peaks have been achieved for the first time. Based on the projection of the EC effect in the electric field-temperature phase diagram, the relationship between the EC behaviors and the phase transitions is further established. It was found that the monoclinic (M) phase actually existed during the transformation from the R phase to the T phase, and the related R-M phase transition and M-T phase transition could both induce negative EC peaks. Under the electric field of E = 10 kV/cm, the first negative EC peaks induced by the R-M phase transition is at 57 °C with ΔT_max = −0.11 K. And the M-T phase transition can produce a higher negative EC peak, and its value can reach −0.22 K at 68 °C. Based on thermodynamic calculations, the relationship between the entropy change in different phase transitions and the EC behaviors has been further elucidated. The negative EC effect originates from the structural entropy increase in the electric field-induced phase transition process. This work not only advances the research on the electrical properties of relaxor ferroelectric single crystals but also provides a new insight into high-performance ferroelectric materials design. Full article

Materials offering high energy density are currently desired to meet the increasing demand for energy storage applications, such as pulsed power devices, electric vehicles, high-frequency inverters, and so on. Particularly, ceramic-based dielectric materials have received significant attention for energy storage capacitor applications due to their outstanding properties of high power density, fast charge–discharge capabilities, and excellent temperature stability relative to batteries, electrochemical capacitors, and dielectric polymers. In this paper, we present fundamental concepts for energy storage in dielectrics, key parameters, and influence factors to enhance the energy storage performance, and we also summarize the recent progress of dielectrics, such as bulk ceramics (linear dielectrics, ferroelectrics, relaxor ferroelectrics, and anti-ferroelectrics), ceramic films, and multilayer ceramic capacitors. In addition, various strategies, such as chemical modification, grain refinement/microstructure, defect engineering, phase, local structure, domain evolution, layer thickness, stability, and electrical homogeneity, are focused on the structure–property relationship on the multiscale, which has been thoroughly addressed. Moreover, this review addresses the challenges and opportunities for future dielectric materials in energy storage capacitor applications. Overall, this review provides readers with a deeper understanding of the chemical composition, physical properties, and energy storage performance in this field of energy storage ceramic materials. Full article

Dielectric ceramic capacitors are highly regarded for their rapid charge–discharge, high power density, and cyclability in various advanced applications. However, their relatively low energy storage density has prompted intensive research aiming at developing materials with a higher energy density. To enhance energy storage properties, research has focused on modifying ferroelectric materials to induce relaxor ferroelectricity. The present study aims to induce a superparaelectric (SPE) state in relaxor ferroelectrics near room temperature by altering BaTiO₃ ferroelectric ceramics using the (Sr,Bi)TiO₃-Bi(Mg_0.5Ti_0.5)O₃ system ((1−x)BT-x(SBT-BMT)). X-ray diffraction and Raman spectroscopy analysis demonstrated a shift in the crystal structure from tetragonal to cubic with an increasing x content. Notably, the compositions (except x = 0.1) satisfied the criteria for the SPE state manifestation near room temperature. The x = 0.2 specimen displayed characteristics at the boundary between the relaxor ferroelectric and SPE phases, while x ≥ 0.3 specimens exhibited increased SPE state fractions. Despite reduced maximum polarization, x ≥ 0.3 specimens showcased impressive energy storage capabilities, attributed to the enhanced SPE state, especially for x = 0.3, with impressive characteristics: a recoverable energy density (W_rec) of ~1.12 J/cm³ and efficiency (η) of ~94% at 170 kV/cm applied field. The good stability after the charge–discharge cycles reinforces the significance of the SPE phase in augmenting energy storage in relaxor ferroelectric materials, suggesting potential applications in high-energy density storage devices. Full article

In this work, were synthesized (Pb_0.91La_0.09)(Zr_0.65Ti_0.35)_0.9775O₃ ceramic materials with different concentrations of praseodymium (0, 0.1, 0.3, 0.5, 1 wt.%) via gel-combustion route and sintered by the hot uniaxial pressing method. Measurements were conducted on the obtained ceramics using X-ray powder diffraction (XRD), scanning electron microscope (SEM), EDS analysis, and examination of dielectric and ferroelectric optical properties. Results give us a detailed account of the influences of the praseodymium ions on the structural, microstructural, and dielectric properties. 3D fluorescence maps and excitation and emission spectra measurements show how a small admixture changes the ferroelectric relaxor behavior to an optically active ferroelectric luminophore. Full article