Antiferroelectric Transition Research Articles

Unveiling a giant electrocaloric effect at low electric fields through continuous phase transition design

The reported electrocaloric (EC) effect in ferroelectrics is poised for application in the next generation of solid-state refrigeration technology, exhibiting substantial developmental potential. This study introduces a novel and efficient EC effect strategy in (1–x)Pb(Lu1/2Nb1/2)O3-xPbTiO3 (PLN-xPT) ceramics for low electric-field-driven devices. Phase-field simulations provide fundamental insights into thermally induced continuous phase transitions, guiding subsequent experimental investigations. A comprehensive composition/temperature-driven phase evolution diagram is constructed, elucidating the sequential transformation from ferroelectric (FE) to antiferroelectric (AFE) and finally to paraelectric (PE) phases for x=0.10−0.18 components. Direct measurements of EC performance highlight x=0.16 as an outstanding performer, exhibiting remarkable properties, including an adiabatic temperature change (ΔT) of 3.03 ​K, EC strength (ΔT/ΔE) of 0.08 ​K ​cm kV−1, and a temperature span (Tspan) of 31 ​°C. The superior EC effect performance is attributed to the temperature-induced FE to AFE transition at low electric fields and diffusion phase transition behavior contributing to the wide Tspan. This work provides valuable insights into developing high-performance EC effect across broad temperature ranges through the strategic design of continuous phase transitions, offering a simplified and economical approach for advancing ecofriendly and efficient solid-state cooling technologies.

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.

Low-temperature stable ferroelectric–antiferroelectric transition for cryogenic energy storage application

The capacitors are in rising demand for cryogenic applications. As for now, it still remains an ongoing challenge for simultaneously achieving high energy storage density and cryogenic temperature stability. Herein, the strategy of stable backward phase transition was demonstrated in the antiferroelectric composition of (Pb0.9175La0.055)(Zr0.975Ti0.025)O3. As a result, we achieved high recoverable energy density about 10 J/cm3 with exceptional low-temperature stability from −160 to 25 °C. Multi-layer ceramic capacitors designed for pulse discharge applications also demonstrated high performance in cryogenic conditions, with the peak current fluctuations of less than 4%. Through in situ characterizations using x-ray diffraction, Raman spectra, and transmission electron microscopy, we discovered that the anisotropic structural evolution is responsible for a stable backward phase transition, providing the material with robust stability at cryogenic temperatures. These results offer a good paradigm for improving the temperature stability of antiferroelectric multi-layer capacitors to meet the rigorous demands of energy storage applications.

Interlayer sliding induced antiferroelectricity–ferroelectricity–antiferroelectricity transition in bilayer δ-SiX (X = S/Se)

There is a reversible antiferroelectric–ferroelectric–antiferroelectric (AFE–FE–AFE) phase transition appearing through mechanical interlayer sliding for bilayer δ-SiX (X =S/Se), bringing up more opportunities for novel volatile devices.

“ μ s P-E curve” and reverse phase transition of antiferroelectric ceramics during ultra-fast charge–discharge

Antiferroelectric materials hold great potential for energy storage applications. However, a significant challenge lies in the disparity ΔW between the rapid discharge energy density Wdis and the recoverable energy density Wre. Quantitative analysis is still lacking, and the ultra-fast reverse ferroelectric–antiferroelectric (FE–AFE) transition behavior at the microsecond scale remains unknown. In this study, a pulse technique was employed instead of the Sawyer–Tower method to obtain the “μs P-E loop” during rapid charge–discharge processes. The “μs P-E curve” clearly illustrates the distinct FE–AFE transition behavior during rapid discharge in comparison to low-frequency conditions. Under pulsed conditions, the FE–AFE transition field was observed to decrease, and even a “remanent polarization” was observed, leading to a reduction in discharge energy during fast discharge. Moreover, through the enhancement of relaxor behavior and the increased diffuseness of FE–AFE switching, the μs P-E loop tended to resemble that observed at low frequencies, thereby resulting in more efficient discharge performance. This study introduced a technique for investigating the ultra-fast FE–AFE transition. Furthermore, it unveiled the origin of ΔW and provided an effective method for achieving high discharge energy density.

2D Antiferroelectric Hybrid Perovskite with a Large Breakdown Electric Field And Energy Storage Density

AbstractEnergy conversion and storage devices are highly desirable for the sustainable development of human society. Hybrid organic–inorganic perovskites have shown great potential in energy conversion devices including solar cells and photodetectors. However, its potential in energy storage has seldom been explored. Here the crystal structure and electrical properties of the 2D hybrid perovskite (benzylammonium)2PbBr4 (PVK‐Br) are investigated, and the consecutive ferroelectric‐I (FE1) to ferroelectric‐II (FE2) then to antiferroelectric (AFE) transitions that are driven by the orderly alignment of benzylamine and the distortion of [PbBr6] octahedra are found. Furthermore, accompanied by field‐induced AFE to FE transition near room temperature, a large energy storage density of ≈1.7 J cm−3 and a wide working temperature span of ≈70 K are obtained; both of which are among the best in hybrid AFEs. This good energy storage performance is attributed to the large polarization of ≈7.6 µC cm−2 and the high maximum electric field of over 1000 kV cm−1, which, as revealed by theoretical calculations, originate from the cooperative coupling between the [PbBr6] octahedral framework and the benzylamine molecules. The research clarifies the discrepancy in the phase transition character of PVK‐Br and shed light on developing high‐performance energy storage devices based on 2D hybrid perovskite.

Highly mismatched antiferroelectric films: Transition order and mechanical state

Epitaxial ${\mathrm{PbZrO}}_{3}/{\mathrm{SrRuO}}_{3}/{\mathrm{SrTiO}}_{3}$ heterostructures are among the most widely studied thin-film antiferroelectrics. This paper explores their temperature-induced phase transitions and the characteristics of the domain structure by means of high-resolution synchrotron x-ray diffraction. The antiferroelectric transition order appears to change from the first to the second; peculiar in-plane $M$-point superstructures develop at high temperatures, manifesting a new phase; the $R$- and $\mathrm{\ensuremath{\Sigma}}$-point superstructure reflections demonstrate much reduced splitting as compared to the demands of the mechanical compatibility. We discuss the energetics of the reduced around-the-normal antiferroelectric domain tilts, its relation to the observed changes in phase transitions, and point to the possible contribution to the observed effect from an unusual diffraction mechanism related to the partial coherence between domains in a random nanodomain structure.

Novel (1-x)NaNbO3-xBi2/3HfO3 based, lead-free compositions with stable antiferroelectric phase and high energy density and switching field

Pulse power devices urgently need lead-free compositions with stable antiferroelectric phase and transition field. Following the guidance of the DFT (Density Functional Theory) calculation, a novel antiferroelectric composition (1-x)NaNbO3-xBi2/3HfO3(0 ≤ x ≤ 0.08), was designed and prepared, exhibiting well-documented double AFE loops both in macro and nanoscale. Furthermore, Bi2/3HfO3 modified compositions also exhibit a high stored energy density of 4.26 J/cm3, forward switching field of 225 kV/cm, large discharge current of 36 A, within 25 ns discharge time and high power density of 32 MW/cm3, which is superior to other NaNbO3-based compositions reported in antiferroelectric range. Structural analysis shows that the high temperature phases of P and R can be rapidly shifted to room temperature by adding Bi2/3HfO3. Combining results from the PFM and TEM, the modified compositions had a faster domain switching speed to the electric field. In addition, theoretical calculations demonstrated that modified compositions have a predictable increasing energy difference −7.48 meV/f.u. between AFE(antiferroelectric) and FE(ferroelectric) phase.

Ferroelectric-Antiferroelectric Transition of Hf1-x Zr x O2 on Indium Arsenide with Enhanced Ferroelectric Characteristics for Hf0.2Zr0.8O2.

The ferroelectric (FE)-antiferroelectric (AFE) transition in Hf1-x Zr x O2 (HZO) is for the first time shown in a metal-ferroelectric-semiconductor (MFS) stack based on the III-V material InAs. As InAs displays excellent electron mobility and a narrow band gap, the integration of ferroelectric thin films for nonvolatile operations is highly relevant for future electronic devices and motivates further research on ferroelectric integration. When increasing the Zr fraction x from 0.5 to 1, the stack permittivity increases as expected, and the transition from FE to AFE-like behavior is observed by polarization and current-voltage characteristics. At x = 0.8 the polarization of the InAs-based stacks shows a larger FE-contribution as a more open hysteresis compared to both literature and reference metal-ferroelectric-metal (MFM) devices. By field-cycling the devices, the switching domains are studied as a function of the cycle number, showing that the difference in FE-AFE contributions for MFM and MFS devices is stable over switching and not an effect of wake-up. The FE contribution of the switching can be accessed by successively lowering the bias voltage in a proposed pulse train. The possibility of enhanced nonvolatility in Zr-rich HZO is relevant for device stacks that would benefit from an increase in permittivity and a lower operating voltage. Additionally, an interfacial layer (IL) is introduced between the HZO film and the InAs substrate. The interfacial quality is investigated as frequency-dependent capacitive dispersion, showing little change for varying ZrO2 concentrations and with or without included IL. This suggests material processing that is independently limiting the interfacial quality. Improved endurance of the InAs-Hf1-x Zr x O2 devices with x = 0.8 was also observed compared to x = 0.5, with further improvement with the additional IL for Zr-rich HZO on InAs.

High dielectric constant, relaxor behavior and phase transitions in Na0.5Bi0.5TiO3 nanorods

We report on relaxor-ferroelectric behavior, ferroelectric to anti-ferroelectric transition and superior dielectric properties of Na0.5Bi0.5TiO3 nanorods synthesized through hydrothermal technique. Na0.5Bi0.5TiO3 nanorods are seen to crystallize in rhombohedral crystal structure. Ferroelectric to anti-ferroelectric transition is observed at 450 K, where the dielectric loss attains its maximum value. Maxwell-Wagner interfacial polarization causes the dielectric constant to be high at room temperature (9 × 105). Dielectric loss at low frequencies is observed to be minimum. Non-Debye relaxation process in Na0.5Bi0.5TiO3 nanorods are clearly seen from the frequency and temperature dependent dielectric studies. Jonscher's relation is employed to analyze the frequency dependent conductivity at various temperatures and the activation energy (Ea) value is observed to be 0.48 ± 0.02 eV. Structural-oxygen vacancy defect-dielectric property correlation is established through a detailed dielectric property analysis in Na0.5Bi0.5TiO3 nanorods.

Synthesis of a New Ferroelectric Relaxor Based on a Combination of Antiferroelectric and Paraelectric Systems.

Relaxor ferroelectric-based energy storage systems are promising candidates for advanced applications as a result of their fast speed and high energy storage density. In the research field of ferroelectrics and relaxor ferroelectrics, the concept of solid solution is widely adopted to modify the overall properties and acquire superior performance. However, the combination between antiferroelectric and paraelectric materials was less studied and discussed. In this study, paraelectric barium hafnate (BaHfO3) and antiferroelectric lead hafnate (PbHfO3) are selected to demonstrate such a combination. A paraelectric to relaxor ferroelectric, to ferroelectric, and to antiferroelectric transition is observed by varying the composition x in the (Ba1-xPbx)HfO3 solid solution from 0 to 100%. It is noteworthy that ferroelectric phases can be realized without primal ferroelectric material. This study creates an original solid solution system with a rich spectrum of competing phases and demonstrates an approach to design relaxor ferroelectrics for energy storage applications and beyond.

Antiferroelectric negative capacitance from a structural phase transition in zirconia

Crystalline materials with broken inversion symmetry can exhibit a spontaneous electric polarization, which originates from a microscopic electric dipole moment. Long-range polar or anti-polar order of such permanent dipoles gives rise to ferroelectricity or antiferroelectricity, respectively. However, the recently discovered antiferroelectrics of fluorite structure (HfO2 and ZrO2) are different: A non-polar phase transforms into a polar phase by spontaneous inversion symmetry breaking upon the application of an electric field. Here, we show that this structural transition in antiferroelectric ZrO2 gives rise to a negative capacitance, which is promising for overcoming the fundamental limits of energy efficiency in electronics. Our findings provide insight into the thermodynamically forbidden region of the antiferroelectric transition in ZrO2 and extend the concept of negative capacitance beyond ferroelectricity. This shows that negative capacitance is a more general phenomenon than previously thought and can be expected in a much broader range of materials exhibiting structural phase transitions.

Structural, dielectric and energy storage characteristics of (Pb1−xSrx)(Zr0.80Ti0.20)O3 antiferroelectric compositions

Antiferroelectric(AFE) and Relaxor ferroelectric(FE) ceramics are most popular for energy storage applications. In our work we have selected compositions near the FE-AFE phase boundary in the quaternary phase PbTiO3(PT)-PbZrO3(PZ)-SrTiO3(ST)-SrZrO3(SZ). Bulk ceramics based on the composition (Pb1−xSrx)(Zr0.80Ti0.20)O3 [PSZT] with 0.14 ≤ x ≤ 0.20 were synthesized by mixed oxide method. XRD and Raman studies were carried out to understand the structural modifications as a function of Sr2+ concentration. Structure refinement using Rietveld method revealed a change from rhombohedral(R3c) for x = 0,to a coexistence of rhombohedral(R3c) and tetragonal(P4mm) for x = 0.15,and tetragonal(P4mm) for x > 0.15. Polarization - Electric field measurements revealed a systematic FE to AFE transition on A-site Sr2+- substitution. Weibull distribution analysis for all PSZT ceramics was carried out to obtain the Breakdown dielectric strength (BDS). Recoverable energy density and energy storage efficiency were evaluated from the P-E hysteresis and have been correlated with their microstructure for their potential energy storage applications.

Static and dynamic strain relaxation associated with the paraelectric-antiferroelectric phase transition in PbZrO3

Order parameter coupling associated with the first order, improper ferroelastic (Pm3̅m - Pbam) transition at ~510 K in PbZrO3 has been analysed from the perspective of strain and elasticity. Formal treatment of spontaneous strains using lattice parameter data from the literature reveals typical coupling with the order parameter for octahedral tilting, Q R, and stronger coupling with the order parameter for antiferroelectric displacements,Q Σ. These indicate that coupling between the two order parameters via common strains is not only biquadratic, λQ 2RQ 2Σ, but may also have contributions from a higher order term, λQ 2RQ 4Σ. Variations of elastic and anelastic properties obtained by resonant ultrasound spectroscopy (RUS) at frequencies in the vicinity of 1 MHz show softening as the transition point is approached from above, discontinuous stiffening at the transition point and a pattern of further stiffening in the stability field of the orthorhombic structure. Below the transition point, the pattern of stiffening resembles the evolution of Q 2R and Q 2Σ, as is typical of coupling dominated by terms with the form λe2Q 2, where e is a spontaneous shear strain. The absence of softening due to terms of the form λeQ 2 implies that the relaxation time for changes in the order parameters in response to an induced shear strain is slower than ~10-6 s. Also in contrast with measurements from the literature made at lower frequencies, no evidence for mobility of ferroelastic domain walls was observed at RUS frequencies. A peak in acoustic loss observed at the transition point and precursor softening in the stability field of the cubic phase are consistent with evidence for local dynamical polar clusters. Apart from some differences in relaxation times, the antiferroelectric transition in PbZrO3 does not appear to be overtly different from ferroelectric transitions such as occur in BaTiO3.

Phase boundary and temperature driven enhanced piezoelectric and electrostrictive strain in (1−2x) Bi0.5Na0.5TiO3-xBaTiO3-xBa0.7Ca0.3TiO3 solid solution

Bismuth-based piezoelectric ceramics are presently of immense interest to researchers as they are believed to be Pb-free alternatives to well-known lead zirconate titanate-based piezoceramics. Herein, the author reports a lead-free ternary solid solution (1−2x)Na0.5Bi0.5TiO3-xBaTiO3-xBa0.7Ca0.3TiO3 (x = 0.01, 0.03, 0.05, 0.07, and 0.09: BNT-BT-BCT) synthesized through a standard solid state reaction route. All the samples crystallized to a complete perovskite structure studied through the powder x-ray diffraction analysis. Rietveld analysis of x-ray diffraction data revealed a structural transformation from monoclinic (Cc) to tetragonal phase (p4mm) with the co-existence of monoclinic (Cc) and tetragonal (p4mm) phases in the samples of x ≥ 0.03. The temperature-dependent dielectric analysis of (x = 0.03 and x = 0.05) systems suggests relaxor characteristics near ferroelectric–antiferroelectric phase transition temperature (Td). A changeover from relaxor to a near normal ferroelectric character was realized for x ≥ 0.07. Furthermore, the existence of polar nano-regions (PNRs) was studied through HR-TEM. Interestingly, a low electric field (±25 kV/cm) driven enhanced piezoelectric [(with 0.22% of strain; Smax/Emax = 850 pm/V for x = 0.03) and (with 0.17% strain and Smax/Emax of 714 pm/V for x = 0.07)] and an electrostrictive [with 0.20% of strain; Smax/Emax = 820 pm/V for x = 0.05] was achieved around Td. This can be attributed to the combined effects of phase boundary, ferroelectric–antiferroelectric transition, and the existence of PNRs.

Multiferroic order parameters in rhombic antiferromagnets RCrO3

Currently, active research is aimed at perovskite—based oxides, including rare earth orthochromites, which exhibit magnetoelectric properties owed to intrinsic magnetic interactions in external electric and magnetic fields. Due to a variety of structural instabilities and couplings in these materials, understanding the underlying magnetoelectric mechanisms is a challenge. In this paper, we explore magnetoelectric properties of the rare earth orthochromites in the framework of symmetry analysis. Our calculations show the presence in RCrO3 of electric dipole moments localized in the vicinity of Cr3+ ions. The electric dipole moments, appearing due to the displacements of oxygen ions from their highly symmetric positions in the parent perovskite phase, are arranged in an antiferroelectric mode. We have demonstrated the presence of electric dipole moments in the unit cell of RCrO3, localized in the vicinity of Cr3+ ions. The inversion symmetry breaks due to the displacements of oxygen ions from their highly symmetric positions in the parent perovskite phase, the electric dipoles become arranged in an antiferroelectric mode. We have introduced the basic distortive order parameters in consistence with the symmetry of RCrO3: the polar order parameters ( D , Q 2, Q 3, P ) and the axial order parameter Ω b and classified them according to the irreducible representations of the RCrO3 symmetry group (D 2h 16). We have determined the symmetry—allowed couplings between distortive, ferroelectric and magnetic orderings and found possible exchange-coupled magnetic and ferroelectric structures. The presented analysis makes it possible to explain experimentally observed polarization reversal and the concomitant reorientation of spins in a series of RCrO3 compounds and to predict the possible scenarios of phase transitions in RCrO3.

The influences of lattice distortion on the antiferroelectric transition and relaxation of oxygen vacancies in high-entropy perovskites (Bi0.2Na0.2Ba0.2K0.2X0.2)TiO3 with X=Ca, Sr or La

High entropy ceramics (HECs) (Bi0.2Na0.2Ba0.2K0.2X0.2)TiO3, X=Ca, Sr or La, with a perovskite structure have been successfully synthesized using a modified citrate acid method. Lattice distortion is a main feature of the HECs which significantly influences their antiferroelectric phase transition behaviors. It is shown that the activation energy of oxygen-vacancy relaxation could quantitatively reflect the lattice distortion of perovskite HECs, as characterized by X-ray diffraction, dynamical mechanical analysis and Raman spectroscopy. Based on the activation energy, the lattice-distortion driven antiferroelectric transition in HECs can be also characterized, providing a viable strategy to design the structural, dielectric and ferroelectric properties as finely tuned by chemical disorder at A or B site in perovskite HECs.

Noncollinear ferrielectricity and morphotropic phase boundary in monolayer GeS

Two-dimensional polarity is intriguing but remains in the early stage. Here a structural evolution diagram is established for GeS monolayer, which leads a noncollinear ferrielectric $\delta$-phase energetically as stable as the ferroelectric $\alpha$-phase. Its ferrielectricity is induced by the phonon frustration, i.e., the competition between ferroelectric and antiferroelectric modes, providing more routes to tune its polarity. Besides its prominent properties like large band gap, large polarization, and high Curie temperature, more interestingly, the morphotropic phase boundary between $\alpha$- and $\delta$-phases is highly possible, which is crucial to obtain giant piezoelectricity for lead-free applications.

A Novel Combinatorial Approach to the Ferroelectric Properties in HfxZr1−xO2 Deposited by Atomic Layer Deposition

Since HfO2‐based ferroelectric films were reported in 2011, several doping/alloying elements have been introduced to secure interesting ferroelectric/antiferroelectric properties of Hf‐based fluorite‐structured thin films. Using a conventional approach by atomic layer deposition (ALD), an enormous number of experiments would be required to reveal the compositional effects of doping/alloying components in ternary and quaternary systems. Therefore, for a comprehensive study of the ferroelectric properties of HfxZr1−xO2, a novel combinatorial ALD technique that enables the fabrication of multicomponent films with a different composition ratio and thickness via saturated/non‐saturated ALD without changing the supercycle of each material is reported. The gradient of the amount of HfO2 over a 100 mm substrate is achieved using a lower Hf‐precursor temperature that results in an insufficient Hf‐precursor dose for saturated deposition. Systematic study on the HfxZr1−xO2 combinatorial library is carried out by spectroscopic ellipsometry, X‐ray photoelectron spectroscopy, and X‐ray diffraction. Furthermore, TiN/HfxZr1−xO2/TiN capacitors are fabricated to measure the remnant polarization. The obtained results clearly show the ferroelectric–antiferroelectric transition according to continuous composition change instead of discrete research. Therefore, a highly productive method for studying ferroelectricity changes in terms of a doping and a composition of HfO2‐based ferroelectric thin films through a novel ALD combinatorial approach is proposed.

Magnetic Properties of NH4H2PO4 and KH2PO4: Emergence of Multiferroic Salts.

We observe sharp step-down discontinuities in the magnetic susceptibility of NH4H2PO4 and NH4H2PO4-d60 (60% deuterated) along the a- and c-axes occurring exactly at their antiferroelectric transition temperatures. For the case of KH2PO4, less pronounced discontinuities occur at the ferroelectric transition temperature. To explain this, we treat the acid protons as individual oscillators that generate current elements that translate to magnetic forces in near resonance with each other. With decreasing temperature, the resonant forces become more commensurate, which amplifies a disproportionate drop off of two types of magnetic forces to eventually trigger the structural phase transitions. For the case of NH4H2PO4, the associated internal magnetic field appears to aid the NH4+ to order at a higher temperature. At 49 K, a shoulder-like anomaly in both NH4H2PO4 and KH2PO4 is attributed to a possible onset of macroscopic quantum tunneling of protons. Our findings bring forth a new category of intrinsic multiferroic systems.