Antiferroelectric Stability Research Articles

Ultrahigh energy storage density and efficiency in A/B-site co-modified silver niobate relaxor antiferroelectric ceramics

AgNbO3-based antiferroelectric ceramics can be used to prepare dielectric ceramic materials with energy storage performance. However, their efficiency is much lower than that of relaxors, which is one of the biggest obstacles for their applications. To overcome this problem, AgNbO3 ceramics co-doped with Eu3+ and Ta5+ at the A- and B-sites were prepared in this work. The Ag0.97Eu0.01Nb0.85Ta0.15O3 sample has a Wr of 6.9 J/cm3 and an η of 74.6%. The ultrahigh energy storage density and efficiency of Ag0.97Eu0.01Nb0.85Ta0.15O3 has been ascribed to the synergistic effect of the increase in the breakdown electric field, the enhancement of antiferroelectric stability, the construction of multiphase coexistence, and the modification of the domain structure morphology. The Ag0.97Eu0.01Nb0.85Ta0.15O3 ceramic is expected to be one of the options for preparing dielectric capacitors.

High energy density in Ag0.5Na0.5(Nb1-xTax)O3 antiferroelectric ceramics

There has been significant interest in AgNbO3-based antiferroelectric ceramics, recently, due to their ability to achieve high energy storage density (Wrec). However, fabricating their commercial products faces challenges due to chemically unstable and expensive Ag2O. To reduce Ag2O contents, we fabricated (Ag0.5Na0.5)(Nb1-xTax)O3 (ANNT100x) ceramics. The results reveal that Ta-substitution plays a dual role: inducing chemical pressure to compress the unit cell along spontaneous polarization direction, enhancing antiferroelectric stability; and increasing the band gap (Eg), boosting intrinsic breakdown strength (Eb). These crucial factors contribute to the enhanced Wrec achieved in ANNT50. Notably, ANNT50 ceramics fabricated by the rolling process exhibit higher Eb (=578 kV/cm) than the conventional process, favoring the complete triggering of “double” polarization with significantly enhanced Wrec (= 6.5 J/cm3). Discharge results indicate that the ceramic displays high power density (Pavg = 78 MW/cm3) and discharge energy (Wdis = 5.86 J/cm3), which can rival currently reported Ag(Nb, Ta)O3 ceramics.

Enhanced energy storage properties of silver niobate antiferroelectric ceramics with A-site Eu3+ substitution and their structural origin

AgNbO3 (AN)-based lead-free antiferroelectric ceramics are widely studied for their use as dielectric capacitor materials. In this study, Eu3+-doped AN ceramics were prepared and the results show that Eu3+ diffused into the AN lattice. The ceramics were formed by M1 and M2 phases coexisting at room temperature, as distinct from the M1 (M: monoclinic) phase of pure AN. Electrical properties and structural characterization showed that the antiferroelectric stability of the ceramics increases with the increase in Eu3+ levels. At room temperature, Ag0.94Eu0.02NbO3 ceramic exhibited a good energy storage density of 5.3 J/cm3 and a high efficiency of 71.9%. When the temperature rises from room temperature to 140 °C, the efficiency of the sample decreases from 80.4% to 67.1% and Wr decreases from 2.1 to 2.0 J/cm3, which indicates that the sample has good temperature stability. The time constant (t0.9) of this sample was less than 60 ns and the power density (PD) was 51.3 MW/cm3, indicating excellent charge–discharge capabilities. This novel ceramic is expected to be used as a new dielectric capacitor material for pulsed power supplies.

Bandgap engineering and antiferroelectric stability of tantalum doped silver niobate ceramics from first-principles

Extensive research has been conducted on silver niobite (AgNbO3)-based antiferroelectric ceramics for their promising applications in energy storage applications, with various compositional modifications explored to improve their energy storage capabilities. In this theoretical study, we have systematically investigated the electronic, structural, and chemical bonding properties of AgNb1-xTaxO3 (x = 0.00, 0.125, 0.25, 0.375, 0.50, abbreviated as ANT100x) solid solutions based on first-principles calculation. Our results reveal that the bandgap increases from 1.82 eV to 1.89 eV, due to the higher energy level of Ta 5d orbitals compared to Nb 4d orbitals. The enlarged bandgap, accompanied with oxygen vacancy formation energy (ΔEf,vac), contributes to the enhancement of Eb. The Ta substitution of Nb site suppresses the cation displacement, oxygen octahedral distortion, and bond length and angles, indicating an improved stability of antiferroelectric phase. In addition, the electron localization function (ELF) and Bader charge values show weakened covalent bonding of Ta−O bonds compared to Nb−O bonds. These theoretical findings have the potential to aid in the advancement and creation of novel energy storage applications using lead-free AFE perovskites, as well as facilitate the manipulation of their breakdown electric field through bandgap engineering.

Stabilizing the anti-ferroelectric phase in NaO–Nb2O5–CaO–B2O3–SiO2–ZrO2 glass-ceramics using the modification of K+ ion

NaNbO3 anti-ferroelectric (AFE) material exhibits a unique and irreversible phase transition, which makes it change into ferroelectric phase and prevents its implementation in high energy storage material. In this work, we use an approach to stabilize the anti-ferroelectric phase at room temperature by the modification of K+ in NaO–Nb2O5–CaO–B2O3–SiO2–ZrO2-xK + glass-ceramics. The correlation between K+ content and anti-ferroelectric stability is studied through the X-ray diffraction, microstructure, and dielectric properties. It is found that ferroelectric phase gradually transforms to anti-ferroelectric phase first and then anti-ferroelectric phase disappears with K+ doping in glass-ceramic due to two mechanisms that the un-crystallized modifier K+ into glass network reduce the connectivity of the glass network, the activation energy needed for crystallization and the tolerance factor (t), besides overmuch K+ into NaNbO3 crystalline phase leads to the increase of tolerance factor and the production of impurity phase. The phase transition has been confirmed through the double polarization loops, AFE phase and permittivity peak. The results show that the K+ doped into NaO–Nb2O5–CaO–B2O3–SiO2–ZrO2-xK + glass system can effectively stabilize AFE phase, when x＞4%, the stability of NaNbO3 anti-ferroelectric phase will decrease and impurity phases will precipitate in glass-ceramic.

AgNbO3-based antiferroelectric ceramics with superior energy storage performance via Gd/Ta substitution at A/B sites

Dielectric materials have attracted considerable attention owing to their excellent power densities and fast charge/discharge characteristics. AgNbO3, as a typical antiferroelectric (AFE) material, is regarded as a promising dielectric material owing to its large polarization value and environmentally friendly nature. However, the low energy density of this system limits its further application. In this study, the slim P-E loops are implemented by Gd/Ta substitution at A/B sites, which provide a superior energy storage performance with a Wrec of 6.99 J/cm3 under 400 kV/cm. This improvement in energy storage property can be attributed to three factors: firstly, a significant improvement in the AFE stability is obtained by reducing the tolerance factor t and the B-site polarizability; secondly, this strategy leads to a reduction in the grain size of the material, optimizing the breakdown electric field Eb of AN-based ceramics; lastly, A/B-site codoping induces structural distortion of the material, constructs an internal chemical pressure, and suppresses its oxide octahedral tilting. Furthermore, the Gd/Ta co-doped ceramics exhibit an excellent practical charging/discharging efficiency (＜10 μs). This work demonstrates that the electrical properties of AN-based ceramics have been optimized by Gd/Ta codoping, making them good candidates for pulsed power systems.

Enhanced energy storage performance in Gd/Mn co-doped AgNbO3 lead-free antiferroelectric ceramics via tape casting

Antiferroelectric materials are promising for applications in advanced high-power electric and electronic devices. Among them, AgNbO3-based ceramics have gained considerable attention due to their excellent energy storage performance. Herein, multiscale synergistic modulation is proposed to improve the energy storage performance of AgNbO3-based materials, whereby the tape casting process is employed to improve the breakdown strength and Gd/Mn doping is utilized to enhance the antiferroelectric stability. As a result, a high recoverable energy storage density up to 5.3 J cm-3 and energy efficiency of 67.6% are obtained in Gd/Mn co-doped AgNbO3 ceramic, which shows good temperature stability and frequency stability. These results show that the components and processes proposed in this work provide a feasible method for improving the energy storage performance of AgNbO3-based ceramics.

Dielectric and Antiferroelectric Properties of AgNbO3 Films Deposited on Different Electrodes

AgNbO3 antiferroelectric materials have become a hot topic due to their typical double polarization–electric field loops. AgNbO3 films usually exhibit superior properties to bulks. In this work, AgNbO3 films were fabricated via the pulsed laser deposition on (001) SrTiO3 substrate with (La0.5Sr0.5)CoO3, LaNiO3 and SrRuO3 bottom electrodes, in which the (La0.5Sr0.5)CoO3, LaNiO3 and SrRuO3 bottom electrodes were used to regulate the in-plane compressive stress of AgNbO3 films. It is found that AgNbO3 films deposited on (La0.5Sr0.5)CoO3, LaNiO3 and SrRuO3 bottom electrodes are epitaxial with dense microstructure. In changing the bottom electrodes from (La0.5Sr0.5)CoO3, LaNiO3 to SrRuO3, the in-plane compressive stress of AgNbO3 thin films becomes weaker, which leads to increased relative dielectric permittivity and reduced antiferroelectric–ferroelectric phase transition electric field EF from 272 kV/cm to 190 kV/cm. The reduced EF implies weakened antiferroelectric stability in AgNbO3 films. It can be seen that the antiferroelectric stability of AgNbO3 films could be regulated by changing the bottom electrodes.

Enhanced energy-storage density in silver niobate ceramics by Yb3+ doping at A-site

High energy density is an important factor for antiferroelectric materials applied in power pulse devices. Herein, the Ag(1-3x)YbxNbO3 (AYNO-100x) ceramics with x = 0, 0.02 and 0.04 were synthesized via a solid-state reaction method in an oxygen atmosphere. The Yb3+ doping at A-site reduces the oxygen vacancy and increases the silver vacancy after reaching saturation, which improves the antiferroelectric stability, leading to enhanced recoverable energy-storage density of 2.7 J/cm3 under 255 kV/cm at room temperature. Meanwhile, a relatively high discharge energy density of 1.0 J/cm3 at 200 kV/cm is also observed in the Ag0.94Yb0.02NbO3 ceramic. These results indicate that AgNbO3 -based ceramics are potential candidates in advanced power electronic devices.

Energy storage performance and phase transition under high electric field in Na/Ta co-doped AgNbO3 ceramics

Lead-free antiferroelectric ceramics with high energy storage performance show great potential in pulsed power capacitors. However, poor breakdown strength and antiferroelectric stability are the two main drawbacks that limit the energy storage performance of antiferroelectric ceramics. Herein, high-quality (Ag1-xNax)(Nb1-xTax)O3 ceramics were prepared by the tape casting process. The breakdown strength was greatly improved as a result of the high density and fine grains, while the antiferroelectric stability was enhanced owning to the M2 phase. Benefiting from the synergistic improvement in breakdown strength and antiferroelectric stability, (Ag0.80Na0.20)(Nb0.80Ta0.20)O3 ceramic reveals a benign energy storage performance of Wrec = 5.8 J/cm3 and η = 61.7% with good temperature stability, frequency stability and cycling reliability. It is also found that the high applied electric field can promote the M2-M3 phase transition, which may provide ideas to improve the thermal stability of the energy storage performance in AgNbO3-based ceramics.

Antiferroelectric stability and energy storage properties of Co-doped AgNbO3 ceramics

AgNbO3 ceramics have attracted progressively more attention to high power energy storage in dielectric capacitors because of complicated in a series of phase transitions. In this work, Ag1-3xBixNb1-3/5xScxO3 (x ​= ​0, 0.005, 0.01, 0.02) ceramics were synthesized via a solid state reaction method in flowing oxygen. The microstructure, dielectric and energy storage properties of as-prepared samples were systematic characterized to evaluate the potential as high energy storage capacitors. A high recoverable energy storage density (3.65 ​J/cm3) and high efficiency (84.31%) were simultaneously obtained in a modified AgNbO3-based ceramic at 21.5 ​MV/m. The energy storage performance is improved by the ions doping that effectively interrupt the dipoles arrangement structure and stabilize the disordered antiferroelectric phase in the long-range order. Co-doping of Bi3+ on the A-site and Sc3+ on the B-site in AgNbO3 is an effective method to enhance the electric field intensity of field-induced phase transitions from antiferroelectric (AFE) to ferroelectric (FE) phases. The M1-M2 phase transition shifted to a lower temperature with an increase in the Bi/Sc amounts, which suppressed the ferroelectricity and obtained pinched-hysteresis loops in modified AgNbO3 ceramics. These results indicate that Bi/Sc co-doped AgNbO3 ceramics are highly efficient lead-free antiferroelectric materials for prospective application in high-performance energy storage capacitors.

NaNbO3 modulated phase transition behavior and antiferroelectric stability evolution in 0.88(Bi0.5Na0.5)TiO3-0.12BaTiO3 lead-free ceramics

Giant strains in (Bi0.5Na0.5)TiO3 based ceramics are usually attributed to electric field induced nonpolar to polar phase transition. Whether it is an ergodic relaxor R3c/P4mm ferroelectric (FE) to long-range ordered FE phase transformation or a reversible P4bm antiferroelectric (AFE) to FE phase transition is still unclear. Herein, lead-free (0.88-x)(Bi0.5Na0.5)TiO3-0.12BaTiO3-xNaNbO3 ceramics exhibit a composition-modulated FE tetragonal P4mm to relaxor AFE tetragonal P4bm phase transition, in which double hysteresis loop, sprout-shaped S-E curves, near-zero quasi-static d33 together with a large volume change suggest the AFE characteristics of P4bm phase. An interesting finding is that the reversibility of field-induced AFE P4bm phase to FE P4mm phase transition strongly depends on the NN content, from being completely irreversible at x = 0.01–0.02, to partially reversible at x = 0.03–0.05, and finally to completely reversible at x = 0.06–0.08. It is indicated that the variation of reversibility should be attributed to the change of relative free energy caused by decreasing the FE to AFE phase transition temperature with increasing the NN content.

Enhanced energy storage properties and antiferroelectric stability of Mn-doped NaNbO3-CaHfO3 lead-free ceramics: Regulating phase structure and tolerance factor

NaNbO3-based ceramics usually show ferroelectric-like P-E loops at room temperature due to the irreversible transformation of the antiferroelectric orthorhombic phase to ferroelectric orthorhombic phase, which is not conducive to energy storage applications. Our previous work found that incorporating CaHfO3 into NaNbO3 can stabilize its antiferroelectric phase by reducing the tolerance factor (t), as indicated by the appearance of characteristic double P-E loops. Furthermore, a small amount of MnO2 addition effectively regulate the phase structure and tolerance factor of 0.94NaNbO3-0.06CaHfO3 (0.94NN-0.06CH), which can further improve the stability of antiferroelectricity. The XRD and XPS results reveal that the Mn ions preferentially replace A-sites and then B-sites as increasing MnO2. The antiferroelectric orthorhombic phase first increases and then decreases, while the t shows the reversed trend, thus an enhanced antiferroelectricity and the energy storage density Wrec of 1.69 J/cm3 at 240 kV/cm are obtained for 0.94NN-0.06CH-0.5%MnO2(in mass fraction). With the increase of Mn content to 1.0 % from 0.5 %, the efficiency increases to 81 % from 45 %, although the energy storage density decreases to 1.31 J/cm3 due to both increased tolerance factor and non-polar phase.

Enhanced energy storage performance under low electric field in Sm3+ doped AgNbO3 ceramics

Herein, Ag1-3xSmxNbO3 (0 ≤ x ≤ 0.025) antiferroelectric ceramics were successfully synthesized by solid state methods. The effect of Sm3+ doping on the structure, property and energy storage performance were studied. With the increasing Sm3+ concentrations, the average grain size decreased. Meanwhile, the stability of high temperature M phases (i.e., the structure between Tf and T3) was expanded, which led to low loss for energy storage. Both of structure analysis and ferroelectric tests revealed the existence of weakly polar/AFE-like phase below Tf. The Sm3+ doping tended to suppress the ferroelectric behavior and expand the stability of antiferroelectricity. Consequently, a significantly enhanced energy storage performance (Wrec = 3.8 J/cm3, η = 73 %) could be achieved in Ag0.97Sm0.01NbO3 ceramic, which was almost 1.5 times larger than that in non-doped AgNbO3 (Wrec = 2.4 J/cm3, η = 45 %) under the similar applied field of 1705 kV/cm±. In particular, the performance of the ceramic showed great temperature stability with variation of ±5 % from 25 °C to 125 °C. These results indicated that the Ag0.97Sm0.01NbO3 ceramic could be an ideal lead-free candidate used in the energy storage field.

Synergic modulation of over-stoichiometrical MnO2 and SiO2-coated particles on the energy storage properties of silver niobate-based ceramics

AgNbO3-based ceramics have been the spotlight for the lead-free dielectric capacitors due to its unique antiferroelectric feature and the ever-increasing environmental concerns. Herein, synergic modulation on the energy storage properties of AgNbO3-based ceramics was reported, in which the over-stoichiometrical introduction of only 0.10 wt% MnO2 at the atomic-scale leads to reduced leakage current, Pr and enhanced antiferroelectric stability while the SiO2 coating on the AgNbO3 particles at the micro-scale greatly inhibits the grain growth, increases the breakdown strength and the electric filed inducing the AFE-FE transitions. As a result, a large recoverable energy density up to 3.34 J/cm3 with efficiency of 60.0% was obtained in 0.10 wt% MnO2-doped AgNbO3@SiO2 ceramic, which is 2.3 times larger than that of the pristine AgNbO3. This work provides a rational approach to synergically modulate the energy storage properties.

Enhanced energy density in Mn-doped (1-x)AgNbO3-xCaTiO3 lead-free antiferroelectric ceramics

Ceramics of 0.2 wt% Mn-doped (1-x)AgNbO3-xCaTiO3 (x = 0.00–0.04) were prepared in flowing oxygen with the solid state method. The microstructure, antiferroelectricity and energy storage performance were investigated to explore the potential for use in energy storage capacitors. Incorporation of CaTiO3 in AgNbO3 effectively inhibits the grain growth and gives rise to high dielectric breakdown strength. The temperature-dependent dielectric property and Raman spectroscopy measurements demonstrate the enhanced stability of antiferroelectricity by CaTiO3 addition through adjusting the M1–M2 phase transition. As a result of both improved antiferroelectricity and dielectric breakdown strength, a high recoverable energy density of 3.7 J/cm3 was achieved in the 2 mol% CaTiO3-modified AgNbO3 ceramic, which represents one of the highest recoverable energy density in recently studied lead-free ceramics. Furthermore, the energy storage performance displays an excellent thermal stability with a low variation (3%) over a wide temperature range (20–120 °C). These results indicate that modifying AgNbO3 simultaneously on the A- and B-sites in the ABO3 perovskite structure may lead to the discovery of new antiferroelectric materials with a high energy density.

Realizing high low-electric-field energy storage performance in AgNbO3 ceramics by introducing relaxor behaviour

Both sustainable development in environment and safety of high-power systems require to develop a novel lead-free dielectric capacitor with high energy density (Wrec) at low applied electric field. In this work, a remarkably high Wrec of 2.9 J/cm3 accompanying with energy storage efficiency of 56% was achieved in Ag0.9Sr0.05NbO3 ceramic at a low applied electric field of 190 kV/cm, by improving anti-ferroelectricity and introducing relaxor behaviour. The improved anti-ferroelectric stability was attributed to the decreased tolerance factor and average electronegativity difference, while the relaxor behaviour was associated with the increased disordered local structure by Sr-doping. Moreover, the Ag0.9Sr0.05NbO3 ceramics also exhibited outstanding temperature stability in energy density with small variation less than 5% over 20–140 °C. The results indicate that the Ag0.9Sr0.05NbO3 ceramic is a promising candidate for low-electric-field driving capacitors.

Evolving antiferroelectric stability and phase transition behavior in NaNbO3-BaZrO3-CaZrO3 lead-free ceramics

The stability of antiferroelectricity in NaNbO3 ceramics was found to evolve with co-doping x mol% CaZrO3 and 6 mol% BaZrO3, from a dominant ferroelectric (FE) orthorhombic Q phase (x = 0) to a gradually stabilized antiferroelectric (AFE) orthorhombic P phase owing to different ionic radii of Ba and Ca ions. Although a complete AFE P phase appears at x = 0.5, the field induced AFE-FE phase transformation is irreversible at first, and then becomes partially reversible at x = 1 and finally completely reversible at x = 3. The above-mentioned change process proves to be associated with the enhancing stability of antiferroelectricity with x, as evidenced by means of dielectric, polarization and strain properties as well as in/ex-situ synchrotron x-ray diffraction and Raman spectra. A composition-field phase diagram for the NN-based lead-free AFE ceramic was constructed on basis of the phase structural change, which would provide a clear understanding of how ion doping influences its antiferroelectricity.

Structure and phase stability of lead-free antiferroelectric (Na0.96−xCa0.04Lix)(Nb0.96Zr0.04)O3 ceramics

(Na0.96−xCa0.04Lix)(Nb0.96Zr0.04)O3 (CZNNL) ceramics with high density were successfully prepared by the solid-state reaction method. The effect of Li dopants on the structure, electrical properties and stability of antiferroelectricity has been investigated. Enhanced antiferroelectric superlattice peaks was observed for CZNNL (x ≤ 0.01) using X-ray diffraction. Li substitution can effectively destabilize the antiferroelectric phase and correspondingly the ferroelectric phase can be enhanced. The field-induced polarization increase and the average grain size decrease with increasing Li concentration. The CZNNL (x = 0.01) ceramics can preserve the double polarization hysteresis loops at room temperature and at 120 °C.

High antiferroelectric stability and large electric field–induced strain in MnO2-doped Pb0.97La0.02(Zr0.63Sn0.26Ti0.11)O3 ceramics

Crystal structure and electrical properties of MnO2-doped Pb0.97La0.02(Zr0.63Sn0.26Ti0.11)O3 antiferroelectric ceramic were studied in detail in this article. X-ray diffraction analysis showed that all specimens took on single tetragonal antiferroelectric structure, and antiferroelectric phase stability enhanced with the increase of MnO2 addition, which was because that the substitution of Mn2+ or Mn3+ with large ion radius for B-site Ti4+ decreased the tolerance factor of the ceramic. In addition, it was observed that different from Mn doping reducing Tm of ferroelectric ceramics, Tm of antiferroelectric ceramics increased with the addition of MnO2, which is for the reason that MnO2 addition enlarged the zone of antiferroelectric phase. Furthermore, by increasing MnO2 content, the strain first increased and then decreased. Meanwhile, the value improved obviously as the measuring frequency decreased. The largest electric field–induced strain of 0.65% was obtained in the specimen with 0.2 mol% MnO2 doping at the frequency of 1 Hz, which lay a foundation for preparing actuator with high strain energy density.