Recoverable Energy Research Articles

Influence of sintering temperature on electrocaloric and energy storage properties of sol-gel derived lead-free BaHf0.20Ti0.80O3 ferroelectric ceramics for sustainable energy solutions

Ferroelectric materials have emerged as intriguing contenders for a variety of applications in the ongoing effort to look for sustainable energy solutions, including energy storage and solid-state cooling systems. In this work, a systematic investigation has been conducted on the microstructural, dielectric, electrocaloric, and energy storage characteristics of sol-gel elaborated BaHf0.20Ti0.80O3 (BHT) ferroelectric ceramics. The structural investigation by Raman and X-ray diffraction indicated that when the sintering temperature increases, the tetragonality of BHT ceramics reduces, and the evolution of the cubic phase increases. The evolution of the microstructure in BHT ceramics is found to be significantly reliant on the sintering temperature. With increasing temperature of sintering, the bulk density of BHT ceramics increases. The improved dielectric and ferroelectric properties were attained in BHT ceramics at higher sintering temperatures. The BHT ceramic sintered at 1350 °C exhibited a maximum electrocaloric temperature change of ΔT ∼0.6 °C with a corresponding efficiency ΔT/ΔE of 0.3 K mm/kV near ambient temperature under a low electric field of 20 kV/cm. The BHT ceramic sintered at 1450 °C exhibited excellent room temperature recoverable energy density of JRec ∼67.84 10−3J/cm3 and high energy storage efficiency of η ∼75.13 % under a low electric field of 20 kV/cm. The highest JRec ∼73.22 10−3J/cm3 with corresponding η of 64.60 % were obtained in BHT ceramic sintered at temperature 1350 °C. These findings broaden the possibility of exploring BHT-based systems as efficient lead-free ferroelectrics for both solid-state refrigeration and energy storage applications.

Toward Design Rules for Multilayer Ferroelectric Energy Storage Capacitors - A Study Based on Lead-Free and Relaxor-Ferroelectric/Paraelectric Multilayer Devices.

Future pulsed-power electronic systems based on dielectric capacitors require the use of environment-friendly materials with high energy-storage performance that can operate efficiently and reliably in harsh environments. Here, a study of multilayer structures, combining paraelectric-like Ba0.6Sr0.4TiO3 (BST) with relaxor-ferroelectric BaZr0.4Ti0.6O3 (BZT) layers on SrTiO3-buffered Si substrates, with the goal to optimize the high energy-storage performance is presented. The energy-storage properties of various stackings are investigated and an extremely large maximum recoverable energy storage density of ≈165.6Jcm-3 (energy efficiency≈93%) is achieved for unipolar charging-discharging of a 25-nm-BZT/20-nm-BST/910-nm-BZT/20-nm-BST/25-nm-BZT multilayer structure, due to the extremely large breakdown field of 7.5MVcm-1 and the lack of polarization saturation at high fields in this device. Strong indications are found that the breakdown field of the devices is determined by the outer layers of the multilayer stack and can be increased by improving the quality of these layers. Authors are also able to deduce design optimization rules for this material combination, which can be to a large extend justify by structural analysis. These rules are expected also to be useful for optimizing other multilayer systems and are therefore very relevant for further increasing the energy storage density of capacitors.

Advancing Energy‐Storage Performance in Freestanding Ferroelectric Thin Films: Insights from Phase‐Field Simulations

AbstractAdvances in flexible electronics are driving the development of ferroelectric thin‐film capacitors toward flexibility and high energy storage performance. In the present work, the synergistic combination of mechanical bending and defect dipole engineering is demonstrated to significantly enhance the energy storage performance of freestanding ferroelectric thin films, achieved through the generation of a narrower and right‐shifted polarization‐electric field hysteresis loop. The recoverable energy storage density of freestanding PbZr0.52Ti0.48O3 thin films increases from 99.7 J cm−3 in the strain (defect) ‐free state to 349.6 J cm−3, marking a significant increase of 251%. The collective impact of the flexoelectric field, bending tensile strain, and defect dipoles contributes to this enhancement. The demonstrated synergistic optimization strategy has potential applicability to flexible ferroelectric thin film systems. Moreover, the energy storage properties of flexible ferroelectric thin films can be further fine‐tuned by adjusting bending angles and defect dipole concentrations, offering a versatile platform for control and performance optimization.

Energy storage properties influenced by relaxor ferroelectric properties dependent on the growth direction of epitaxial Bi2SiO5 thin films

Ferroelectric Bi2SiO5 (BSO) thin films were deposited by pulsed laser deposition on Nb-doped (100), (110) and (111) SrTiO3 (Nb:STO) substrates, resulting in (001)-, (113)- and (204)-oriented epitaxial films. Due to the crystallinity of BSO, in which the Bi2O2 layers are formed perpendicular to the c-axis direction, the (001)-oriented epitaxial BSO thin film showed the lowest remanent polarization and the best leakage current characteristics. On the other hand, the (113)- and (204)-oriented films showed an increase in remanent polarization due to the improvement of a-oriented crystallinity. Through experiments using vertical and lateral piezoresponse force microscopy, it has been confirmed that the distribution of in-plane-oriented domains reducing remanent polarization decreases in the order of (001)-, (113)- and (204)-oriented epitaxial BSO thin films. The epitaxial BSO thin films that exhibit ferroelectric hysteresis loops similar to the relaxor ferroelectric thin films tended to have improved energy storage characteristics as a result of improved remanent polarization and saturation polarization. In particular, the (113)-oriented epitaxial BSO thin film showed a high recoverable energy density of about 41.6 J cm−3 and an energy storage efficiency of about 85.6%.

Superior energy-storage density and ultrahigh efficiency in KNN-based ferroelectric ceramics via high-entropy design

The rapidly advancing energy storage performance of dielectric ceramics capacitors have garnered significant interest for applications in fast charge/discharge and high-power electronic techniques. Simultaneously improving the recoverable energy storage density Wrec and efficiency η becomes more prominent at the present time for their practical applications. Herein, a high-entropy concept is implemented on the (K0·5Na0.5)NbO3 (KNN)-based ferroelectric ceramics to design the high-performance dielectric capacitors. First, the strong lattice distortion can absorb some electric energy during the electrical loading process and result in the delayed polarization saturation. Additionally, the large composition fluctuations induce the weak correlation between polar nanoregions and enhance the η. Finally, the high-entropy design and viscous polymer processing method reduce the grain size and improve the Eb. In consequence, excellent Wrec of 11.14 J/cm3 with high η of 87.1% are achieved under an electric field of 750 kV/cm in the high-entropy component. These results demonstrate that the high-entropy concept is a potential avenue to design the KNN-based high-performance dielectric energy storage capacitors.

Enhanced electrocaloric response and energy storage in [(Bi0.5Na0.5)0.94Ba0.06]0.975Sr0.025TiO3 ceramic close to room temperature

Lead-free [(Bi0.5Na0.5)0.94Ba0.06]0.975Sr0.025TiO3 (BNBTS25), with morphotropic phase boundary, has attracted considerable attention due to its depolarization temperature, Td (Ferroelectric (FE)- Antiferroelectric (AFE) transition), which is in close proximity to room temperature (322K). Therefore, the research on electrocaloric and energy storage was limited to temperatures ranging from 223K to 363K. BNBTS25 presents firstly an intensive interests as promising candidate for environmental-friendly energy storage products. This material provides a good recoverable energy density up to Wrec = 577 mJ/cm3 with an energy-storage efficiency of η = 68% in the vicinity of Td. The origin of enhanced energy storage performance is discussed from a scientific point of view. Secondly, BNBTS25 exhibits a high electrocaloric effect (ECE), including an adiabatic temperature change of ΔT = 1.24 K and an electrocaloric responsivity of ξ = 0.301K.mm/kV was observed under an electric field of E = 40 kV/cm at a temperature near 290K. This high ECE performance exceeds that of several reported lead-free ceramics and even performs better than some lead based ceramics. The obtained results suggest that BNBTS25 ceramic is a promising candidate for both electrocaloric and energy storage applications in operating temperature such as cooling in microelectronic devices.

Simultaneously enhanced of energy storage and energy harvesting performances of [(Bi0.5Na0.5)TiO3–BaTiO3] ceramics by addition of SrTiO3

As is well known, relaxor dielectrics are characterized by high energy storage efficiency (η), while high recoverable energy storage density (Wrec) can be achieved by anti-ferroelectric ceramics. Herein, our approach is to find relaxor- anti-ferroelectric coexistence phases of (Bi0.5Na0.5)TiO3- BaTiO3 ceramics for achieving high performance in energy storage and energy harvesting as well. Therefore, [(0.9-x) ( Bi0.5Na0.5)TiO3-xSrTiO3-0.1BaTiO3] (abbreviation (0.9-x) NBT-0.1BT-xST) (0.0 ≤ x ≤ 0.4) were synthesized via the solid-state reaction route in air. The tolerance factor (τ) increased from 0.9901 to 0.9998 when ST-content increased from 0.0 to 0.4, indicating an increase in crystal lattice symmetry. The FT-IR de-convolution vibration modes shown in the TiO6 octahedra exhibit two peaks at ∼550 and 650 cm−1, which indicate present coexistence phases of the crystal structure. Ferroelectric to relaxor phase crossover has been detected by the addition of ST with the present anti-ferroelectric phase in particular dopant ST = 0.2. The increasing into the diffused phase transition (γ) is signified by enhancement of the relaxor degree of NBT-BT at high content of ST. The rapidly suppressed remnant polarization (Pr) at high content of ST is due to substitute iso-valence (Sr2+) by tri-valence (Bi3+) and mono-valence (Na1+). Ultrahigh Wrec = 1.13 J/ cm3 with excellent η = 92.62% were obtained at ST = 0.3 at low electric field (E = 110 kV cm−1). A remarkable response of the strain with a high converse piezoelectric coefficient ( d33* = 390.47 pm V−1) at ST = 0.2 was obtained due to decreasing the non-revisable 180° domain switching. Based on the obtained results, the addition of ST to NBT-BT ceramics can provide a head start in the implementation of ceramic capacitors for potential effective into energy harvesting and energy storage applications.

Ultrahigh breakdown strength of NaNbO3‐based dielectric ceramics for high‐voltage capacitor application

AbstractDielectric ceramics have attracted significant attention in power electronic systems, owing to their exceptional charging and discharging speeds, as well as their high power density. However, simultaneously achieving a high recoverable energy density (Wrec) and high efficiency (η) in high‐voltage dielectric ceramics remains a challenge for applications where a high breakdown electric field (Eb) is required. In this study, high‐quality (1 – x)NaNbO3–xSr0.7Bi0.2(Mg1/3Nb2/3)O3 [(1 – x)NN–xSBMN] ceramics were prepared based on an optimization strategy combining phase structure with microstructural regulation. A quasilinear P–E loop with negligible hysteresis was realized in the ceramic with x = 0.4, excellent Wrec of 5.61 J/cm3, and high η of 85.1% obtained at a largely improved Eb of 710 kV/cm. To the best of our knowledge, the Eb of 710 kV/cm is one of the highest values achieved in dielectric ceramics to date. The noticeable reduction in grain size (∼0.95 µm) and increased bandgap improve the Eb to an ultra‐high level, which is a crucial factor in high energy storage density. The coexistence of a few antiferroelectric phases and the dominant paraelectric phase is the structural origin of the comprehensive energy‐storage performance improvement. Therefore, our research develops a unique approach to unleash the potential in NaNbO3‐based ceramics, holding great promise for application in high‐voltage dielectric capacitors.

Ultrafast discharge properties and enhanced energy density in lead‐free NaNbO3‐based relaxor ferroelectric ceramics

AbstractNaNbO3‐based (NN) energy storage ceramics are known for exhibiting high maximum polarization (Pmax) and large recoverable energy density (Wrec). However, the huge energy loss density (Wloss) has been a limiting factor in improving energy storage performance. Therefore, a ternary system was designed to achieve both huge Wrec and efficiency (η). The combination of 0.35Bi(Zn0.5Ti0.5)O3–0.65BaTiO3 (BZTBT) was chosen to reduce grain size and disrupt the long‐range ordered domains, thereby inducing the polar‐nano‐regions to mitigate Wloss. The optimal performance was achieved with the 0.75NaNbO3–0.25(0.35Bi(Zn0.5Ti0.5)O3–0.65BaTiO3) (0.75NN–0.25BZTBT) ceramic, which exhibited a high Wrec = 2.68 J/cm3 and superior η = 82.7% under 310 kV/cm. Remarkably, the 0.75NN–0.25BZTBT ceramic displayed an exceptionally fast discharge time to 90%, t0.9 = 88 ns, coupled with a huge energy density Wd = 0.95 J/cm3. This study demonstrates the significant potential of 0.75NN–0.25BZTBT ceramic in the realm of energy storage and rapid charge–discharge applications.

Enhanced energy-storage properties in (Bi0.5Na0.5)TiO3 ceramics by doping linear perovskite materials Ca0.85Bi0.1(Sn0.5Ti0.5)O3

For energy storage applications in Bi0.5Na0.5TiO3 (BNT)-based materials, the key challenges are the premature polarization saturation and low breakdown electric field (Eb), which confine the energy storage capacity of BNT and significantly restrict progress in advancing pulsed power capacitors. Hence, the cooperative optimization strategy of band structure and defect engineering was proposed, which successfully obtained a high recoverable energy density of 3.83 J/cm3 and an energy efficiency of 77.9 % in the Bi0.5Na0.5TiO3-0.12Ca0.85Bi0.1(Sn0.5Ti0.5)O3 (BNT-0.12CBST) ceramics. Doping the BNT matrix with CBST has been shown to not only reduce grain size but also enhance relaxor behavior, which collectively improves breakdown strength and delays polarization saturation. Furthermore, the x = 0.12 ceramic also exhibits a commendable discharge power density of 91.9 MW/cm3 and a transient discharge time of 40 ns. The higher resistivity and lower oxygen vacancy concentration are conductive to acquire superior breakdown electric field and energy storage performance. We determine the crystal structure, dielectric and ferroelectric properties of the studied ceramics in a wide range of temperatures and concentrations, and a phase diagram is constructed, which illustrates the complex phases present and their transformation behavior. Our work provides an effective strategy to optimize the energy-storage of dielectric ceramics, and shows great potential for practical applications in pulse power systems.

Optimize energy storage performance of NaNbO3 ceramics by multivariable control strategy

NaNbO3 ceramics have broad application prospects in ultra-high power electronic systems, electromagnetic pulses, and other applications. In this study, (1-y)[(1-x)NaNbO3-xSmMg0.5Zr0.5O3]-y(Bi0.5Na0.5)0.7Sr0.3TiO3 (x = 0.06, 0.08 and 0.10)(y = 0.30, 0.35, 0.40 and 0.45) ceramics were fabricated. The effects of the incorporation of SmMg0.5Zr0.5O3 (SMZ) and (Bi0.5Na0.5)0.7Sr0.3TiO3 (BNST) on the energy storage performance, impedance, actual charge and discharge capacity, phase structure and microstructure of the ceramic samples were analyzed. Finally, when x = 0.08, and y = 0.35, the recoverable energy storage density of the sample was 5.8 J/cm3 and a high energy storage efficiency of 88 % was obtained at 545 kV/cm. In addition, the ceramic maintains a stable actual charge and discharge capacity and an extremely fast discharge time (16.1 ns) in a wide temperature range (20–160 °C). These excellent energy-storage performances may be due to the fine grain size and large relaxation and activation energies.

Combined Supercritical CO2 Brayton Cycle and Organic Rankine Cycle for Exhaust Heat Recovery

Abstract In order to reduce energy consumption and related CO2 emissions, waste heat recovery is considered a viable opportunity in several economic sectors, with a focus on industry and transportation. Among different proposed technologies, thermodynamic cycles using suitable organic working fluids seem to be promising options, and the possibility of combining two different cycles improves the final recovered energy. In this paper, a combination of Brayton and Rankine cycles is proposed: the upper cycle has supercritical carbon dioxide (sCO2) as its working fluid, while the bottomed Rankine section is realized by an organic fluid (organic Rankine cycle (ORC)). This combined unit is applied to recover the exhaust energy from the flue gases of an internal combustion engine (ICE) for the transportation sector. The sCO2 Brayton cycle is directly facing the exhaust gases, and it should dispose of a certain amount of energy at lower pressure, which can be further recovered by the ORC unit. A specific mathematical model has been developed, which uses experimental engine data to estimate a realistic final recoverable energy. The model is able to evaluate the performance of each recovery subsection, highlighting interactions and possible trade-offs between them. Hence, the combined system can be optimized from a global point of view, identifying the most influential operating parameters and also considering a regeneration stage in the ORC unit.

Enhanced magnetoelectric and energy storage performance of strain-modified PVDF-Ba0.7Ca0.3TiO3-Co0.6Zn0.4Fe2O4 nanocomposites

The experimental development of thin films that exhibit higher room-temperature low-field magnetoelectric (ME) sensing without compromising reliable electrical energy storage capabilities is rare. Here, an improved ferroelectric polarization, ME coupling and energy storage performance of polymer-based nanocomposites, which find applications in portable high-power dielectric capacitors, are studied. Multiferroic nanofiller-based three-phase flexible nanocomposites, polyvinylidene fluoride (PVDF)-(Ba0.7Ca0.3)TiO3-(Co0.6Zn0.4)Fe2O4, were fabricated using compression molding to enhance polarization which is pivotal for applications. PVDF with a high β-phase content (92.4 %), switchable ferroelectric behavior and higher breakdown strength (510 kV/mm) was obtained under optimized process conditions (500 MPa at 165 °C). The fabrication assisted alteration of intermolecular chain distance results in a tensile strain (1.42 %) of β-crystallites corresponding to an internal stress of ~21 MPa. The progressive increase of nanofiller content has led to enhanced polarization (11 μC/cm2), soft ferromagnetic properties, and enhanced ME coupling of 59 mV/cm-Oe due to switchable magnetostriction (λ11 = −18 ppm and dλ11/d = −22 × 10−9 Oe−1) at lower saturation field of 1.2 kOe. The ME sensitivity was found to be more than two-folds enhanced compared to solution-cast films making them prospective self-biased flexible devices for wearable electronics. Simultaneously, enhanced change of magnetization (19.6 %) under electric field was obtained. Detailed energy storage characteristics confirm that the nanofiller inclusion up to 7.12 vol% effectively improved the recoverable energy storage density (21.2 J/cm3) with an efficiency of 67 %. The experimental and simulation results corroborate a significantly improved breakdown strength of 617 kV/mm with reliable performance. Thus, careful processing provides viable polymer dielectrics with beneficial storage characteristics.

Moderation of [Bi3+/Na1+] molar ratio for enhancement of dielectric and energy storage properties of NaNbO3 ceramics

Lead-free (Na1−3xBix)(Nb0.75Ti0.25)O3 (x = 0.0, 0.05, 0.1, 0.125 and 0.15) (NN-BT) ceramics were synthesized using solid-state reaction technique. The effect of Bi3+ into the crystal structure, dielectric, ferroelectric and energy storage properties of NNT ceramics were investigated. Pure NNT shows present perovskite structure with orthorhombic crystal structure at x ≤ 0.125, while Na3NbO8-NaNbO3 composite phase has been detected at x = 0.15. The tolerance factor (τ) decreased from 0.97 (x = 0.0) to 0.82 (0.15) which signified the composition deviated from perovskite structure at 0.15. Significant enhancement of dielectric constant at room temperature has been achieved by increasing Bi-content and the maximum value (∼1500) obtained at 0.1. The largest value of maximum polarization (Pmax) and smallest value of remnant polarization (Pr) were achieved at x = 0.1 due to orthorhombic NaNbO3 and rhombohedral (Na0.5Bi0.5)TiO3 coexistence phases. The substitution of monovalent (Na1+) by trivalent (Bi3+) lead to create sodium vacancies into the A-sites of NNT lattice subsequently increased the cations disorder and charge misfit. The maximum recoverable energy storage density (Wrec = 17.5 J cm−3) and energy storage efficiency (η = 80%) were achieved at x = 0.1, E ∼ 700 kV cm−1. Partially, (NNTB0.1) exhibit an outstanding stability of energy storage properties in terms of temperature range (25 to 150 °C) and frequency stability (2–20Hz). The present results imply the moderation ratio of Bi/Na plays an important role for enhancement of energy storage properties of NaNbO3 anti-ferroelectric ceramics.

Improving energy storage properties of NN-NBT ceramics through compositional modification

Na0.5Bi0.5TiO3(NBT)-based ceramics are materials with good energy storage properties and non-ergodic relaxation ferroelectric properties, as well as high Curie temperature and good temperature stability. Herein, a new approach was devised to adjust the non-ergodic relaxation ferroelectric characteristics of Na0.5Bi0.5TiO3(NBT)-based ceramics by introducing NaNbO3 into Na0.5Bi0.5TiO3(NBT) (x NN-(1-x) NBT, where x= 0.17, 0.19, 0.21, 0.23, and 0.25). To overcome limitations of NBT, additional constituents with antiferroelectric properties were introduced to create binary solid solutions with NBT to yield NN-NBT ceramics with antiferroelectric properties for optimized energy storage applications. As-obtained NN-NBT ceramics revealed multiphase structures with rhombic (R3c) and tetrahedral (P4bm) phases. Coexisting strongly and weakly coupled polar nanoregions (PNRs) resulted in relatively high polarization (Pmax) and reduced polarization of reflection (Pr). The optimized 0.21NN-0.79NBT ceramic exhibited recoverable energy storage density of ≈2.84 J·cm−3 at 180 kv·cm−1 with energy storage efficiency of 78%. Structural characterization indicated the existence of intermediate phases modulation phases with coexisting antiferroelectric phase and relaxation ferroelectric phase. Overall, proposed NBT-based non-ergodic relaxation ferroelectric ceramics look promising for effectively improving energy storage performance, providing new prospects for the development of advanced pulse capacitors.

Design, synthesis and Characterization of a novel antiferroelectric solid solution (1-x)PbHfO3-xBiAlO3

Antiferroelectric (AFE) materials are potentially useful for energy storage applications. Lead hafnate (PbHfO3) is one of the prototypical AFE materials. However, its critical field (Ecr) which is needed to induce the AFE to ferroelectric phase transition is close to the dielectric breakdown strength. To reduce Ecr, we prepare the solid solutions of (1-x)PbHfO3–xBiAlO3 (x = 0.00–0.04) via solid state synthesis. The crystal structures, dielectric behaviour, ferroelectric properties, and energy storage properties are investigated. A temperature-composition phase diagram is established. At room temperature, the crystal symmetry of all compositions is orthorhombic with the Pbam space group. Upon heating, the transition to the AFE orthorhombic Imma phase is observed at the temperature TC1, which slightly decreases with increasing x, followed by the transition to the cubic phase at the temperature TC2, which does not depend on x. Distinct dielectric anomalies are observed at TC1 and TC2. It is found that BiAlO3 substitution reduces Ecr and the polarization–electric field relations display characteristic double hysteresis loops. For x = 0.04, at a comparatively small applied field of 130 kV/cm, the values of recoverable energy density (Wrec) and efficiency of 0.24 J/cm3 and 84 %, respectively, are obtained. At 190 °C, a Wrec = 0.75 J/cm3 and a very high efficiency of 92 % are obtained at the field of 50 kV/cm. Thus, the prepared material can potentially be used in high-temperature pulsed power capacitors for energy storage applications within the temperature range from room temperature up to 190 °C.

Ultrahigh energy storage performance in AN-based superparaelectric ceramics

Ceramics capacitors, especially featuring antiferroelectric (AFE) structure, are widely used in pulsed power electronic systems due to distinctive high-power density and external field stability. Lead-free AFE material AgNbO3 has seized substantial research attention owing to its unique temperature driven multi-level phase transitions, and many works have greatly improved the energy storage properties by engineering these temperature-dependent phase boundaries. In this work, an ever-unadopted strategy was proposed to modulate the relaxor structure in AgNbO3 by designing room-temperature (RT) superparaelectric phase via Bi incorporation into AN lattice matrix. Structural analysis shows M phase (space group Pbcm) evolves into O phase (space group Cmcm) with 12 mol.% Bi-substitution, breaking the long-range AFE order into polar nanoregions. Hence, an ultra-high recoverable energy density (7.6 J/cm3) and a high efficiency (79 %) are simultaneously achieved in the Ag0.64Bi0.12NbO3 ceramics under 52.2 kV/mm. Moreover, the excellent energy storage properties are accompanied with good temperature and frequency stability, with the variation of Wrec less than ± 15% (over 25–120 °C) and ± 10% (over 1–200 Hz) under 25 kV/mm, respectively. The novel approach reported herein provides a new guidance for designing AgNbO3-based and other AFE materials for high-performance energy storage applications.

Synthesis and Characterization of the Electrical and Energy Storage Properties of New Barium Titanate - Europium Titanate Solid Solution

In the present work, the investigation of the structural, dielectric, ferroelectric and energy storage properties of polycrystalline samples of (1-x)BaTiO3 – xEuTiO3 (BT-ET) solid solution materials prepared by conventional solid-state reaction method has been carried out. X-ray diffraction analyses have revealed the formation of a single-phase tetragonal structure with the P4mm space group. Furthermore, the temperature dependence of the dielectric constants marked the presence of the following sequence of structural phase transitions, namely from rhombohedral to orthorhombic, from orthorhombic to tetragonal and from tetragonal to cubic phase transitions with the increase of temperature. A diffuse phase transition has been observed from the dielectric permittivity peak and has been analyzed using the modified Curie-Weiss law and the degree of diffuseness is found to be in the range of 1.16 - 1.76 due to the existence of different states of polarization. A phase diagram has been established based on the temperature-dependent dielectric permittivity studies. The room temperature ferroelectric properties point to a coercive field larger than that of BaTiO3 ceramics. Broad dielectric peaks associated with diffuse phase transition appear in a wide temperature range (40 - 100 °C) with the highest dielectric permittivity ε’ = 6498 found in the x = 0.05 ceramics. Moreover, an improved energy storage performance is obtained in the 0.95BaTiO3-0.05EuTiO3 ceramic with a recoverable energy density of Wrec = 0.797 J/cm3, coupled with an efficiency η = 73% at 170 kV/cm and the highest storage energy density of Wst = 1.571 J/cm3 is obtained for 0.90BaTiO3-0.10EuTiO3, which is superior to other lead-free BT-based ceramics. All these features demonstrate that the BT-ET ceramics can be widely used in energy storage applications and also in high-temperature multilayer capacitors for automotive, aerospace and related industries.

Enhanced energy storage performance of Na0.5Bi0.5TiO3-based relaxor ferroelectric ceramics by synergistic optimization strategies

Despite the fact that Na0.5Bi0.5TiO3 (NBT) based lead-free ceramics have attracted widespread interest due to their various advantages, their lower recoverable energy storage density (Wrec) and energy storage efficiency (η) limit their development in pulsed power capacitors. In this work, we propose a synergistic optimization strategy to enhance the energy storage performance of 0.65Na0.5Bi0.5TiO3-0.35SrTiO3(NBST) based lead-free ceramics by introducing Bi0.8La0.2(Ni0.5Zr0.5)O3 (BLNZ) and employing viscous polymer process (VPP). The former converts the macroscopic domains into microscopic domains, limiting the polarization response hysteresis to give a large Pm–Pr. The latter reduces the thickness and porosity of the samples, resulting in a substantial increase in breakdown strength. Ultimately, by stepwise optimization of this strategy, the x = 0.15 ceramic by VPP (0.15VPP) achieves excellent energy storage performance (Wrec = 7.6 J/cm3, η = 92%) under 620 kV/cm and reliable temperature stability from 20-140 °C. The combined excellent results of this study show that our synergistic optimization strategy can effectively enhance the energy storage performance of NBT-based dielectric ceramics and could be further extended to other ceramic materials for pulsed power capacitors.

Ultrahigh Energy Storage Density and Efficiency in Orthorhombic PLZST Antiferroelectric Ceramics via Composition Regulation.

PbZrO3-based antiferroelectric (AFE) ceramic materials have emerged as potential candidates for the next generation of high-energy multilayer ceramic capacitors (MLCCs) because of their distinctive characteristics of double hysteresis loops. The energy storage efficiency of orthorhombic AFE ceramics with ultrahigh storage density is relatively low, which hinders their practical application. In this study, the low efficiency limit of PLZST-based orthorhombic ceramics was overcome by precisely adjusting the Sn4+ content in the (Pb0.95Ca0.02La0.02)(Zr0.99-xSnxTi0.01)O3 AFE ceramics. On one hand, the addition of Sn4+ disrupts the original long-range dipole and improves the rapid response of polarization reversal under the applied voltage. As a result, the difference in electric hysteresis under an electric field is reduced, leading to a significant improvement in energy storage efficiency. On the other hand, increasing the Sn4+ content suppresses the formation of oxygen vacancies, inhibiting grain growth and strengthening grain bonding. This results in ceramics with a high breakdown field strength. Ultimately, the resulting PLCZST ceramics reveal an expressively improved recoverable energy density of 10.2 J cm-3 together with a high energy efficiency of 91.4% under a high applied electric field of 560 kV cm-1. The present study demonstrates the tunability of performance in orthorhombic PLZST AFE ceramics, thereby introducing a ceramic material with exceptional energy storage capabilities for MLCC applications.