Relaxor Ferroelectric Behavior Research Articles

Investigation on Relaxor-Ferroelectric Behavior of BNBT-KNN Ceramics with Ta Doping

Investigation on Relaxor-Ferroelectric Behavior of BNBT-KNN Ceramics with Ta Doping

Structural, dielectric and magnetic properties of MFeNbO6 materials (M=Ti, Zr, Hf)

We study the structural, magnetic and electronic properties of MFeNbO6 materials (where A = Ti, Zr or Hf). TiFeNbO6 crystallises with the disordered rutile structure with the P42/mnm space group. Increasing the ionic radii of the M4+ cation going from Ti4+ (0.605 Å) to Zr4+ (0.72 Å) and Hf4+ (0.710 Å) results in a buckling of the octahedral chains with these materials crystallising with the disordered α-PbO2 structure (space group Pbcn). In contrast, with previous reports for TiFeNbO6 we find no evidence of relaxor ferroelectric behaviour with all three materials instead exhibiting Maxwell-Wagner-like relaxation. Impedance spectroscopy confirms semiconductor behaviour. Magnetically, all three materials can be described by infinite irregular antiferromagnetic S = 5/2 chains with weak ferromagnetism below 10 K. These chains have random directions of propagation between nearest Fe–Fe neighbours consistent with the disordered nature of these materials. We observed a negative imaginary part of the ac susceptibility related to the defect magnetic topology.

Innovative Design of BNKT-xSLZT Ceramics: Maximizing the Polarization Difference for Enhanced Energy Storage.

Lead-free relaxor ferroelectric ceramics with outstanding energy-storage (ES) density (Wrec) and high ES efficiency (η) are crucial for advanced pulse-power capacitors. This study introduces a strategic approach to maximizing the polarization difference (ΔP) by inducing a transition from the ferroelectric phase to the ergodic relaxor (ER) phase. By employing this strategy, a series of ceramics, (1 - x)(Bi0.5Na0.4K0.1)TiO3-x(Sr0.85La0.1)(Zr0.5Ti0.5)O3 (BNKT-xSLZT), with varying SLZT content (x = 0.05, 0.10, 0.15, and 0.20), were designed. The addition of SLZT enhances cationic disorder, induces vacancies at A sites, and disrupts long-range ferroelectric order, facilitating the formation of polar nanoregions and enhancing relaxor ferroelectric behavior. Furthermore, a viscous polymer process (VPP) technology is employed to optimize the ceramics' structure, aiming to increase the breakdown strength (Eb) and enhance ΔP. Ultimately, enhanced ES performance is demonstrated in BNKT-0.15SLZTVPP, achieving a remarkable Wrec of 6.85 J/cm3 and η of 84% under 470 kV/cm. This composition demonstrates excellent stability with minimal variations in Wrec (3.0%) and η (4.4%) over the temperature range of 20-110 °C. Additionally, BNKT-0.15SLZTVPP exhibits exceptional pulse charge-discharge properties, featuring a high discharge density of 3.72 J/cm3, a large power density of 164.2 MW/cm3, and a short discharge time (t0.9) of 193 ns under 300 kV/cm. The study validates the practicality of BNKT-0.15SLZTVPP for pulse capacitors and underscores the potential to enhance ES performance through A-site donor doping and VPP technology. This work provides a comprehensive understanding of the interplay among composition, structure, and ES properties in lead-free relaxor dielectric ceramics, laying the groundwork for innovative advancements in the field.

Enhanced temperature stability of piezoelectric properties and electrostrain via a diffused phase transition in LaMnO3-doped (K, Na)NbO3-based ceramics

Modern-generation electronic devices face a significant challenge in enhancing the temperature stability of their electrical properties, which are crucial for their practical applications. This study introduces an effective approach to diffused phase engineering, involving doping LaMnO3 to induce diffused phase transition. Consequently, the material achieves temperature-insensitive piezoelectric properties and electrostrain. We combine temperature-dependent X-ray diffraction, first-principle calculations, and other dielectric/piezoelectric properties to elucidate the relationship between dopants, structures, and properties in the (0.96-x)K0.48Na0.52NbO3-0.04Bi0.5Na0.5ZrO3-xLaMnO3 systems. Additionally, LaMnO3 doping in KNN-based ceramics maintains long-range ferroelectric order (LRFO) and enhance ferroelectric relaxor behavior, thereby optimizing the electrical properties (such as the d33*of ∼400 pm/V and the TC of ∼300 °C) of ternary co-doped systems. The normalized unipolar strain (Suni/SRT) exhibits a variation of less than 12.2% over the temperature range of 25–150 °C, while d33 at 200 °C retains 80% of its value at 25°C. Moreover, LaMnO3 doping leads to an increase in both depolarization temperature (Td) and d33. Overall, this study provides an effective paradigm for balancing Td and d33 and designing the composition of temperature-insensitive commercial piezoelectronic devices.

Atomic resolution microstructure study of Bi-doped SrTiO3

Intrinsic SrTiO3 is a quantum paraelectric, but moderately Bi-doped SrTiO3 exhibits dielectric frequency dispersion similar to relaxor ferroelectrics. In this paper, detailed electron microscopic studies of the microstructures of Bi-doped SrTiO3 samples were presented. It was found that the Sr sites were replaced by off-central Bi, resulting in tensile strain in the strontium titanate (STO) lattice. In the Bi-doped SrTiO3 samples, the valence of titanium mainly showed the Ti[Formula: see text] characteristic. According to the dielectric behavior and microstructure analysis, the polar nanoregions (PNRs) composed of strained SrTiO3 nanoclusters should be responsible for the ferroelectric relaxor behavior in samples with moderate Bi content.

Titanate-based high-entropy perovskite oxides relaxor ferroelectrics

Different combinations of monovalent and trivalent A-cations in high-entropy perovskite oxides (HEPOs) were investigated. The multicomponent (A′0.2A″0.2Ba0.2Sr0.2Ca0.2)TiO3 (A′ = Na+, K+, A″ = Bi3+, La3+) perovskite compounds were successfully synthesized by solid-state reaction method persisting average cubic perovskite phase. The trivalent cation exhibited distinct effects on local structure, dielectric properties and relaxor ferroelectric behavior. Highly dense ceramics (> 95%), high dielectric constant (~ 3000), low dielectric loss (~ 0.1), and relaxor ferroelectric characteristics were obtained in the compound containing Bi3+. The La3+ containing compounds revealed lower dielectric constant, higher dielectric loss and linear dielectric behavior. The effect of monovalent cation on the dielectric properties was minimal. However, it affected relaxor ferroelectric behavior at elevated temperatures and conduction behavior at high temperatures. The (K0.2Bi0.2Ba0.2Sr0.2Ca0.2)TiO3 ceramic maintained the relaxor ferroelectric behavior with low PREM at high temperatures suggesting more stable relaxor ferroelectric characteristics than that of the (Na0.2Bi0.2Ba0.2Sr0.2Ca0.2)TiO3. Moreover, between these two compounds, the homogeneous electrical characteristics could be obtained from the compound consisting of K + and Bi + at A-site. This study suggests that tuning the chemical composition, particularly choosing appropriate combination of mono/trivalent cations in high entropy perovskite oxides, could be the effective approach to develop high-performance relaxor ferroelectrics with the desired properties.

Improved relaxor ferroelectrics and energy storage performance of polycrystalline Ba0.95Sr0.05Ti2O5 ceramics modified with La dopants

Lead-free relaxor ferroelectrics are useful in energy storage applications. In particular, BaTi2O5-based dielectric materials may have great potential for such applications. In this study, polycrystalline Ba0.95Sr0.05Ti2O5-xLa (BST2-xLa) ceramics were synthesized using a standard solid-state reaction method with as-prepared nanoparticles prepared via a modified Pechini polymeric precursor method. The structural and electrical properties of the BST2-xLa ceramics were systematically investigated using a series of measurements. The phase analysis results confirm that La3+ is a donor dopant that replaced Ba2+ sites in the structure, which results in a decrease in oxygen vacancies to maintain charge neutrality. The intrinsic electronic conduction mechanism for electrical conductivity was evaluated from the fitted activation energy based on the Arrhenius equation. The relaxor ferroelectric behaviour and energy storage density and efficiency are improved by the addition of a small amount of lanthanum (<3.6 mol%) because of the charge and ionic radius mismatch in the structure. These results suggest that lanthanum can effectively optimise the relaxor ferroelectrics of BST2-xLa ceramics, which have promising potential as energy storage materials.

Effect of rare earth oxides on the energy storage performance of Sr0.7Bi0.2TiO3 ceramics

In this study, Sr0.7Bi0.2TiO3 (SBT) ceramics doped with Y2O3, Dy2O3 and Gd2O3 rare earth oxides were designed and prepared by the conventional solid-state reaction method. The results show that all ceramics exhibit typical relaxor ferroelectric behavior, and the breakdown strength (BDS) of SBT ceramics is improved. Among them, Sr0.7Bi0.15Y0.05TiO3 ceramics demonstrate excellent energy storage performance, with a high recoverable energy density (Wrec ) of 2.4 J/cm3 and an efficiency (η) of 88.1% under 290 kV/cm. Furthermore, Y2O3-doped SBT ceramics exhibit a rapid discharge speed of 0.05 µs and a high power density (PD ) of 144.1 MW/cm3 under 300 kV/cm in charge-discharge tests. These characteristics have significant potential in pulse power applications.

Ferroelectric relaxor behaviour in Bi and K/Na-substituted solid solutions of tetragonal tungsten bronze PbNb2O6

Lead metaniobate (PbNb2O6 or PNO) belongs to the tetragonal tungsten bronze (TTB) family. There are three polymorphic forms of PNO: tetragonal (stable at high temperature), rhombohedral (stable at room temperature), and the metastable orthorhombic phase, which has ferroelectric properties. The metastable orthorhombic phase is formed by quenching from the high temperature tetragonal phase due to the reconstructive/sluggish tetragonal to rhombohedral phase transition. A suitable ionic substitution can also lead to the stable ferroelectric orthorhombic phase. Stabilization of the ferroelectric orthorhombic phase by ionic substitution, and the formation of ferroelectric relaxors with increased amounts of dopants is hereby reported for the compositions Pb(1-x)Bi(x/2K(x/2)Nb2O6 and Pb(1-x)Bi(x/2)Na(x/2)Nb2O6. The solid solutions of PNO showed evidence of linked dielectric relaxation and ferroelectricity, validating the distinctive ferroelectric relaxor behaviour for the compositions Pb0.6Bi0.2K0.2Nb2O6 and Pb0.6Bi0.2Na0.2Nb2O6. As the concentrations of bismuth (Bi) and potassium/sodium (K/Na) dopants increased, the Curie temperature (Tc), or the temperature corresponding to the maximum dielectric permittivity (Tm), dropped. By using the Uchino-Nomura relation as a modification of the Curie-Weiss law, it was established that the Pb0.6Bi0.2K0.2Nb2O6 solid solution exhibit higher degree of diffuseness than Pb0.6Bi0.2Na0.2Nb2O6 at the transitions. The width of the ferroelectric hysteresis loop increased as the percentage of dopants increased, from x = 0.1 to x = 0.3. At x = 0.4, a narrow ferroelectric hysteresis loop and a frequency-dependent Tm abruptly formed, which is indicative of a ferroelectric relaxor.

Investigation of Praseodymium Ions Dopant on 9/65/35 PLZT Ceramics’ Behaviors, Prepared by the Gel-Combustion Route

In this work, were synthesized (Pb0.91La0.09)(Zr0.65Ti0.35)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.

Tunable electrocaloric effect in selective ferroelectric bilayers via electrostatics for solid-state refrigeration and microelectronics thermal management

Ferroelectric (FE) electrocaloric materials research has been blossoming worldwide for solid-state refrigeration and potential cooling systems replacing thermoelectric Peltier coolers in microelectronics. In this work, we report the outcomes from a systematic study of combined phase transition (thermodynamics) based on the phenomenological Landau theory and distributed electric field (electrostatics of thin film interfaces) in FE bilayer films. Specifically, the compositional variation of ferroelectric bilayers results in broken spatial inversion symmetry leading to asymmetric thermodynamic potentials due to a combination of normal (first- and second-order phase transition) and relaxor (dispersive dielectric constant) ferroelectric behaviors devised for efficient electrocaloric cooling effects. Extensive theoretical analyses conducted for bilayers consisting of insulating materials highlight modified phase transition temperature behavior and self-poling by effective electric field amplification arising due to bilayers’ electrostatic coupling yielding significant changes in isothermal entropy (ΔS) and adiabatic temperature (ΔT). The theoretical calculation insights supported with experimental results signify, through case studies for a combination of materials experimental parameters, that amplification of the local electric field and materials engineering maximize the number of coexisting phases at or away from the morphotropic phase boundary of constituent layers in bilayer thin film architectures, which can be applicable toward other classes of materials and multilayer systems. These are effective ways for efficient cooling, in general, and for microelectronics thermal management either directly or by developing a thermal switch with phase change materials integrated with thermoelectric coolers for residual heat dissipation, both at the system and on-chip levels.

Creep in 0.91(Na1/2Bi1/2)TiO3-0.06BaTiO3-0.03K0.5Na0.5NbO3 lead-free piezoceramic under constant electric field loads

This work explores the creep behavior of polycrystalline 0.91(Na1/2Bi1/2)TiO3-0.06BaTiO3-0.03K0.5Na0.5NbO3 under constant electric fields. It reveals intriguing time-dependent variations in both polarization and strain response, which can be attributed to a transformation from the relaxor state to a long-range ferroelectric order. Meanwhile, bulk volume resistivity values are obtained to eliminate the influence of leakage current on the polarization assessment. The findings provide valuable insights into the creep behavior of lead-free relaxor ferroelectrics, laying a solid foundation for enhancing the performance and reliability of piezoactuators.

Relaxor Ferroelectric AgNbO3 Film Fabricated on (110) SrTiO3 Substrates via Pulsed Laser Deposition

AgNbO3-based materials have attracted extensive attention in energy storage due to their double hysteresis loops, but they suffer from low breakdown strength (Eb). AgNbO3 films with few defects and small thickness exhibit high Eb, which helps to improve the energy storage performance. In this work, we successfully prepared AgNbO3 thin films on (110) SrTiO3 substrate using pulsed laser deposition technology. The AgNbO3 film shows good crystalline and relaxor ferroelectric behavior. A high Eb up to 1200 kV/cm is obtained in AgNbO3 film, which contributes to good recoverable energy storage density Wrec up to 10.9 J/cm3 and energy efficiency η of 75.3%. Furthermore, the Wrec remains above 2.9 J/cm3 and the η varies between 72.5% and 82.5% in a wide temperature range of 30–150 °C. This work reveals the great potential of relaxor ferroelectric AgNbO3 film for energy storage.

Effect of ferrite phase addition on Pb-Free multiferroic composite material for energy storage applications

Bulk composite ceramics exhibit promising potential as energy storage materials due to their strong ferroelectric characteristics. To lessen the use harmful Pb based material, multiferroic composite combining ferrite and perovskite ceramics with piezoelectric and ferroelectric traits, have gained prominence for high-efficiency energy systems such as ceramic capacitor. This study focuses on a dual-phase multiferroic ceramic composite, following the formula (1-x) Ba0.77Ca0.23TiO3 + xNi0.6Zn0.25La0.15Fe2O4 (x = 0.0, 0.1, 0.2, and 0.3), prepared via a solid-state reaction process. XRD analysis confirms the presence of cubic perovskite (BaTiO3) and cubic spinel ferrite (NZLFO) phases. SEM images depict uniform microstructures with sporadic pore formations, which decreased in grain size with ferrite addition. The P-E loops reveal relaxor ferroelectric behavior with near-zero remnant polarization (Pr), indicating its suitability as an energy storage medium. The highest energy density efficiency, approximately 54 %, was achieved at x = 0.1. The addition of more than 10 % ferrite significantly affects both the microstructure and energy storage properties.

Modulation of magnetic and dielectric properties by Al3+ substitution in Ca3CoMnO6 ceramics

We report a detailed study of the influence of non-magnetic Al3+ doping on the microstructure, magnetic, and dielectric characteristics Ca3CoMnO6. The introduction of Al3+ leads to the suppression of competing short-range magnetic orders, a gradual disappearance of the spin freezing peak in Ca3CoMn1-xAlxO6 was observed, accompanied by the release of magnetic frustration. Moreover, a weakening of the antiferromagnetic order in Ca3CoMnO6 was attributed to the dilution effect induced by non-magnetic Al3+ within the Co-Mn-Co-Mn spin chains. The dielectric measurements exhibit excellent agreement with the magnetic measurements. The substitution of Mn4+ with Al3+ results in the attenuation of relaxor ferroelectric behavior, accompanied by a decrease in the static freezing temperature Tf and an increase in the activation energy Ea. It indicates that Al3+ substitution could well suppress the formation of polar nanoregions. With introducing Al3+ the magnetodielectric effect of Ca3CoMnO6 is also significantly enhanced. For the x = 0.15 sample, the magnetodielectric effect undergoes a notable variation of approximately 10 % under a magnetic field of H = 4 T.

High-entropic relaxor ferroelectric perovskites ceramics with A-site modification for energy storage applications

With the growing concept of developing smart cities, the demand for evolving eco-benign and efficient energy storage applications with extraordinary performance has risen significantly. To overcome such high demands, configurationally complex composites/alloys are engineered by populating the single lattice site of perovskite materials deliberately with distinct cations to create highly entropic form of materials. Herein, two high entropy ceramics (Ba0.2Na0.2Ca0.2Sm0.2Bi0.2)TiO3 (BNCSBT) and (Ba0.2Na0.2Mg0.2La0.2Bi0.2)TiO3 (BNMLBT) are deliberately engineered to analyze their structural, ferroelectric and dielectric capacitive performance. XRD analysis, tolerance factor and Rietveld refinement of measured XRD patterns of the ceramics have confirmed the Cubic symmetry with Pm3‾m space group. Both BNCSBT and BNMLBT ceramics have demonstrated the maximum polarization (Pmax) of 26.3 μC/cm2 and 28. 02 μC/cm2, recoverable energy density (Wrec) of 1.0715 J/cm3 and 1.1225 J/cm3 and energy conversion efficiency (ƞ) of 81.42% and 80.12% respectively. Moreover, the temperature dependent dielectric analysis of BNCSBT and BNMLBT ceramics has presented the wide transition temperature effect due to the creation of polar nano-regions, confirming the relaxor ferroelectric behavior with diffusion coefficient values of 1.8312 and 1.8021 respectively. Such engineered high-entropic ceramics with excellent relaxor ferroelectric and dielectric capacitive performances even at the high temperature (120 °C) are phenomenal for temperature dependent energy storage applications.

Synergistic modulation of ferroelectric polarization and relaxor behavior of Sr2NaNb5O15‐based tungsten bronze ceramic

AbstractDeveloping dielectric ceramics with high energy storage performance (ESP) is essential for miniaturizing and integrating high‐power pulse capacitors. Sr2NaNb5O15‐based tungsten bronze ferroelectric ceramics have been highly investigated for dielectric energy storage applications recently. However, the difficulty in concurrently obtaining large polarization and strong relaxor characteristics greatly hinders the ESP improvement. In this work, Bi3+ and Ti4+ ions were introduced into the Sr2NaNb5O15 ceramic, aiming to modulate the ferroelectric polarization and relaxor behavior synergistically. An excellent recoverable energy density (Wrec ∼ 4.08 J/cm3) and a high efficiency (η ∼ 84.59%) were concurrently attained in the Sr1.85Bi0.15NaNb4.85Ti0.15O15 composition due to the boosted polarization and enhanced relaxor nature. Moreover, this ceramic also exhibited a high current density (863.06 A/cm2) and a large power density (94.94 MW/cm3). All these characteristics demonstrate that the Bi3+ and Ti4+ ions co‐doped Sr2NaNb5O15 ceramics possess great potential for dielectric capacitor applications.

Giant Energy Density via Mechanically Tailored Relaxor Ferroelectric Behavior of Pzt Thick Film.

Relaxor ferroelectrics (RFEs) are being actively investigated for energy storage applications due to their large electric-field-induced polarization with slim hysteresis and fast energy charging-discharging capability. Here, w e report a novel nanograin engineering approach based upon high kinetic energy deposition for mechanically inducing the RFE behavior in a normal ferroelectric Pb(Zr0.52 Ti0.48 )O3 (PZT), which results in simultaneous enhancement in the dielectric breakdown strength (EDBS ) and polarization. Mechanically transformed relaxor thick films with 4μm thickness exhibited an exceptional EDBS of 540 MV/m and reduced hysteresis with large unsaturated polarization (103.6 μC/cm2 ), resulting in a record high energy storage density of 124.1 J/cm3 and a power density of 64.5 MW/cm3 . This fundamental advancement is correlated with the generalized nanostructure design that comprises of nanocrystalline phases embedded within the amorphous matrix. Microstructure-tailored ferroelectric behavior overcomes the limitations imposed by traditional compositional design methods and provides a feasible pathway for realization of high-performance energy storage materials. This article is protected by copyright. All rights reserved.

A New Relaxor Ferroelectrics Ba4SrBiTi3Nb7O30 with Tungsten Bronze Structure

This paper reports the synthesis, microstructure and electrical properties of a new Ba4SrBiTi3Nb7O30 ceramic. X-ray diffraction analysis shows that the sample crystallizes into tungsten bronze structure, and the space group is P4bm. The electrical measurement results show that Ba4SrBiTi3Nb7O30 exhibits good dielectric and ferroelectric properties. The temperature-dependent dielectric permittivity indicates that the transition temperature of the prepared Ba4SrBiTi3Nb7O30 sample is around Tm ≈ 250K. With increasing the frequency, the dielectric peak moves to a lower temperature. Below 250 K, obvious polarization current can be detected, corresponding to the formation of spontaneous ferroelectric polarization. These results indicate the relaxor ferroelectric behavior of Ba4SrBiTi3Nb7O30 ceramic.

Rare Earth Doped Lead Zirconate Titanate Thin Films for Memory and Power Device Applications

We fabricated thin films of (PbZr0.53Ti0.47)O3 (PZT) and (PbZr0.53Ti0.47)0.90(LaxSc1-x)0.10O3 where; x= 0, 0.2, 0.4, 0.6 and 0.8 denoted as [abbr. PL10x] PL0, PL2, PL4, PL6, and PL8 respectively on the LSMO buffer layer (bottom electrode) by using a PLD technique. The X-ray diffraction peaks show a single-phase perovskite structure of thin films with a preferred (100) orientation that coincides with the MgO and has tetragonal phase symmetry (P4mm). Pt electrodes were deposited at the top of thin films as top electrodes. We achieved higher dielectric permittivity (ε’) for PL0 and PL6 compared to other compositions. We noticed that the role of increasing lanthanum content (decreasing scandium) resulted in the broadening of ε’ with temperature and ferroelectric phase transition decreased to 450 K. However, the scandium doping alone (PL0) didn’t lower the ferroelectric phase transition. We analyzed the temperature-dependent ε’ using the modified Curie-Weiss law. The PL0, PL6, and PL8 thin film capacitors exhibited relaxor ferroelectric properties that were further supported by the Vogel-Fulcher relation.The P-E hysteresis loops exhibited the role of lanthanum and scandium causing compositional changes in coercive fields. The P-E loops of PZT, PL2, and PL4 exhibited typical ferroelectric features. Whereas, PL0, PL6, and PL8 showed a relaxor ferroelectric behavior which was corroborated by the analysis of the dielectric data. The PL0 and PL6 thin films showed better spontaneous polarization Ps. We achieved superior energy storage performance Ure = 54.63 J/cm3 with η ~ 70% for PL0 and Ure = 26.54 J/cm3 with η ~ 66% for PL8 thin film capacitors. The study demonstrated the idea that by tuning La3+ and Sc3+ the dielectric and ferroelectric properties of thin films can be controlled for suitable electronic applications, such as memory, power devices, and energy storage.