Antiferroelectric Phase Transition Research Articles

Antiferroelectricity of titanite-type oxide SrTiGeO5 and its potential for power electronics applications

Antiferroelectric materials have recently received renewed attention due to the increased demand for energy-storage ceramics and power electronics applications. This study demonstrates antiferroelectricity in a titanite-type oxide, SrTiGeO5, through direct observation of a double D-E hysteresis loop by polarization measurements. Temperature dependence of dielectric permittivity shows a cusp around 550 K, indicating a relatively high antiferroelectric phase transition temperature for SrTiGeO5. It is suggested that an electric-field-induced rise of permittivity in SrTiGeO5 has the potential for application in protective circuits of power electronics devices. The present study paves the way for the development of innovative antiferroelectric applications.

Negative Thermal Expansion Caused by the Antiferroelectric Phase Transition in Lead-Free Perovskite Ceramics

Due to the structural stability and high adjustability of perovskite, lead-free perovskite ceramics are widely thought to be one of the most promising functional materials. In this work, an abnormal negative thermal expansion behavior with a linear expansion coefficient of −54.95 ppm/K is achieved in the (1-x)NaNbO3-xCaZrO3 system by driving the antiferroelectric phase transition from orthorhombic phase and tetragonal phase. The NTE mechanism is verified by temperature-dependent high-energy synchrotron X-ray diffraction, dielectric spectra, and Raman scattering spectroscopy. The relationship between the antiferroelectric phase transition and negative thermal expansion behavior is systematically revealed by analyzing the evolution of the phase structure with temperature. This novel negative thermal expansion feature caused by the antiferroelectric phase transition provides new guidance for designing more negative thermal expansion materials.

Pressure-induced ferroelectric and anti-ferroelectric phase transitions in LaN

Pressure-induced ferroelectric and anti-ferroelectric phase transitions in LaN

Study of Structural and Electrical Properties of Li and Nb Modified BNT Thin Film and Observation of Enhanced Electrocaloric Effect near Room Temperature

A detailed investigation was done on Li and Nb modified Bi0.5Na0.5TiO3 (BNT) thin films where structural, dielectric, ferroelectric and electrocaloric properties were studied. All thin films were synthesized using pulsed laser deposition. Structural investigation revealed that addition of Li and Nb do not alter the parent rhombohedral structure and all compositions were observed to have rhombohedral structure. However Ferroelectric and dielectric analysis clearly revealed that addition of Li and Nb affect the Ferroelectric (FE) -Antiferroelectric (AFE) phase transition temperature (T d , depolarization temperature) and bring it down towards the room temperature and consequently a mixed phase of FE and AFE was observed near room temperature for composition x = 0.06. A sudden change in polarization in x = 0.06 composition with increasing temperature, subsequently leading to significantly high (∂P/∂T) E along with FE-AFE transition contributed to large electrocaloric (ΔT) = − 4.32 K in composition x = 0.06 ∼ 35 °C.

Differences of the temperatures of ferroelectric and magnetic phase transitions of perovskites

Binary and ternary AB′0.5 B″0.5O3 oxides with a complex perovskite structure, possessing the consecutive ferroelectric or antiferroelectric phase transitions at T C and ferromagnetic, antiferromagnetic, or ferrimagnetic phase transitions at T N, are considered together with classical ferroelectrics and antiferroelectrics. The common correlations between these temperatures, their differences T С-T N and interatomic bond A-O (δ AO) or B-O (δ BO) strains are revealed. Some common correlations between their temperatures T С, T N, T С-T N differences, and δ AO or δ BO are revealed. It is established that these differences for multiferroics are in common dependences with classical ferroelectrics and antiferroelectrics.

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.

Effect of holding time on microstructure, ferroelectric and energy-storage properties of Pb0.925La0.05Zr0.95Ti0.05O3@SiO2 ceramics

Antiferroelectric materials are considered promising energy storage materials because they have excellent energy density during the antiferroelectric phase transition. Herein, Pb0.925La0.05Zr0.95Ti0.05O3@SiO2 (PLZT@SiO2) core-shell structure ceramic materials were synthesized by combing sol-gel method with conventional solid-phase method. The effect of holding time (3 h, 6 h, 9 h, 12 h) on the electrical properties and energy storage properties of PLZT@SiO2 ceramics were investigated. TEM results indicate the formation of a core-shell structure. Transmission electron microscope (TEM) reveals the formation of core-shell structure. X-ray diffraction (XRD) obtained clear tetragonal perovskite structure PLZT and SiO2 phase. The phase transition temperature of PLZT@SiO2 ceramics is between 222 °C and 225 °C, and its dielectric constant can be adjusted by the holding time. The PLZT with surface coated SiO2 can increase the breakdown electric field (BDS) and thus increase the energy density. When the holding time is 9 h, the breakdown electric field is as high as 156.84 kV/cm, and the recoverable energy density (Wre) is 1.92 J/cm3, which is mainly determined by its high density and breakdown electric field.

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.

Thermal and Nuclear Quantum Effects at the Antiferroelectric to Paraelectric Phase Transition in KOH and KOD Crystals.

Crystalline KOH undergoes an antiferroelectric (AFE) proton ordering phase transition at low temperatures, which results in a monoclinic bilayer structure held together by a network of weak hydrogen bonds (HBs). The Curie temperature shifts up when the compound is deuterated, an effect that classical MD is not able to catch. For deeper insights into the transition mechanism, we carry out ab initio MD simulations of KOH and KOD crystals by including quantum effects on the nuclei through Feynman path integrals. The geometric isotope effect and the evolution of the lattice parameters with temperature agree with the experimental data, while the purely classical description is not appropriate. Our results show that deuteration strengthens the HBs in the low-T AFE ordered phase. The transition is characterized by the flipping of OH/OD groups along a bending mode. Above the transition, the system is driven into a dynamical disordered paraelectric phase.

Effect of La(Nb1/3Mg2/3)O3 addition on phase transition behavior and energy storage properties of NaNbO3 ceramics

The doped NaNbO3 ceramics of (1−x)NaNbO3–xLa(Nb1/3Mg2/3)O3 were prepared by conventional solid state method, and then the dielectric, phase transition and energy storage performances were investigated. The X-ray diffraction results showed a phase transition from orthorhombic to rhombohedral occurred with the increase of x. The introduction of additives induced the first-order anti-ferroelectric phase transition and decrease of phase transition temperatures. As a result, an enhanced recoverable energy storage density of 1.45 J cm−3 was observed when x = 4.5% with an efficiency of 69.6% under a moderate electric field. The thermal hysteresis phenomenon was attractive not only in chemical modification but also in the enhancement of energy storage properties. This will contribute to the promotion of NaNbO3-based dielectric capacitors.

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.

Phase transition properties of ferroelectric and antiferroelectric liquid crystals

ABSTRACT Thermodynamic models based on the Landau free-energy density are popular and well suited to study the phase transition properties of ferroelectric and antiferroelectric liquid crystals. Ferroelectric and antiferroelectric liquid crystals have molecular chirality which play an important role in the technology of liquid crystals for the application of devices performance. The structural properties of ferroelectric phase transitions which give rise to the macroscopic tensors coupled to the macroscopic fields, the parameters describing the antiferroelectric phase transitions are still under investigation due to the lack of precise symmetrical properties characterising their existence. The study of ferroelectric and antiferroelectric liquid crystals has been substantial experimental strides. In theoretical approach, there has been relatively inappreciable work on this fascinating class of material. The present review paper focused on a comprehensive overview of the current scenario of the phase transition properties of ferroelectric and antiferroelectric liquid crystals for the fundamental and technological applications. The Landau Ginzburg theory of the phase transitions between ferroelectric and antiferroelectric liquid mesophases is investigated. The important experimental and theoretical developments of ferroelectric and antiferroelectric mesogens are also summarised.

Dielectric properties and infrared spectra of Ag0·92Li0·08NbO3 ceramics

The dielectric properties of Ag0·92Li0·08NbO3 (ALN8) ceramics were investigated in a broad frequency range (20 Hz −90 THz). The dielectric spectra of ALN8 ceramics mainly are impacted by the electrical conductivity at higher temperatures (above 500 K) and low frequencies (below 1 MHz) and the contribution of the soft relaxation mode, which frequency is below 50 cm−1. The electrical conductivity has two anomalies close to antiferroelectric and ferroelectric phase transition temperatures, respectively. The most pronounced decrease of the activation energy is observed close to the ferroelectric phase transition temperature. The values of activation energies are typical for oxygen vacancies transport. Some phononic modes are slightly temperature dependent close to the ferroelectric phase transition temperature confirm the influence of Ag, Nb and Li ions dynamics on the phase transitions.

Enhanced Bipolar Strain and Electrocaloric Response in Gadolinium/Tantalum Co-Substituted Sodium Bismuth Titanate Lead-Free Ceramics

High performance piezoelectric materials with an ABO3 perovskite structure have received growing attention in recent research due to their technological applications in sophisticated research, medical and defence devices like piezoelectric sensors, transducers, ultrasonic motors, nano-positioners, actuators and imaging devices, etc. The technical utility of these materials stems from the various possibilities they offer for cation substitution in the A (or) B sites, which provide valuable opportunities for the optimization and tailoring of desired properties. To date, lead based perovskites, such as lead zirconate titanate (PZT), PZN-PT, and PMN-PT materials, have been extensively investigated in the literature. Although lead based materials exhibit highest piezoelectric coefficients, their wide-scale application has often been hampered by considering the toxicity of lead and its effect on environment and health. This triggered the search for alternative materials that could replace the lead-based ceramics and results in less-hazardous production methods, use and recycling. This has led to a continuous search of potentially attractive alternative lead-free ceramic materials to their counterpart lead based materials for specific applications. Among various kinds of lead-free piezoelectric materials, Na0.5Bi0.5TiO3 (NBT)-based materials are considered to be promising candidates for replacing the lead-based materials. They have been extensively investigated by the condensed materials physics community because of their complicate phase transitions and superior piezo-response. Compared to various chemical substitutions, tantalum (Ta) substitution provides superior electro-strain for the NBT- based ferroelectrics, while the effect of tantalum oxide additive was rarely reported. Gd3+ and Ta5+ co-substituted (Na0.5Bi0.497Gd0.003)Ti1-xTaxO3 (NBGT-Tax) lead-free piezoelectric ceramics are synthesized by using hydrothermal technique. The influence of Ta5+ substitution on the sintering, microstructure, phase transition, and various electrical properties of NBGT ceramics was investigated. Tantalum substitution has no remarkable effect on the microstructure and densification within the studied doping composition. The X-ray diffraction studies revealed that both NBGT-Tax (x=0.000) and NBGT-Tax (x=0.003) ceramics exhibited single phases monoclinic crystal structure with Cc phase. However, with substitution of tantalum the antiferroelectric phase zone gets broader. Simultaneously, the temperature for a ferroelectric to antiferroelectric phase transition is reduced along with an increase in temperature for a transition from antiferroelectric phases to paraelectric phases. This results indicate that tantalum occupies B site of the perovskite structure behaving as a donor, producing A-site cation vacancies. The undoped NBGT ceramics shows good ferroelectric and piezoelectric properties (remnant polarization Pr = 34.2 μC/cm2). The value of remnant polarization was found to increase with Ta substitution along with an increase in coercive field as shown in the figure attached. This is because of the ferroelectric properties being influenced by composition and its homogeneity, defects, external field and orientation of domains, which eventually contributed to the materials response. Meanwhile, the addition of Ta leads to an increase in the electro-strain, together with a higher normalized strain. Moreover, the materials with temperature dependent polarization can be used for solid state cooling applications. The NBGT-Tax compositions shows decrement in the remnant polarization with the increasing temperature which causes increment in the change in entropy. Consequently, the material exhibits the conventional electrocaloric effect (ECE). This simultaneous presence of large field-induced bipolar strain and ECE response along with isothermal change in entropy opens window for great potential applications in the field of electronic devices. Figure 1

Enhanced pyroelectric response from domain-engineered lead-free (K0.5Bi0.5TiO3-BaTiO3)-Na0.5Bi0.5TiO3 ferroelectric ceramics

Enhanced pyroelectric response is achieved via domain engineering from [001] grain-oriented, tetragonal-phase, lead-free 0.2(2/3K0.5Bi0.5TiO3-1/3BaTiO3)-0.8Na0.5Bi0.5TiO3 (KBT-BT-NBT) ceramics prepared by a templated grain growth method. The [001] crystallographic orientation leads to large polarization in tetragonal symmetry; therefore, texturing along this direction is employed to enhance the pyroelectricity. X-ray diffraction analysis revealed a Lotgering factor (degree of texturing) of 93 % along the [001] crystallographic direction. The textured KBT-BT-NBT lead-free ceramics showed comparable pyroelectric figures of merit to those of lead-based ferroelectric materials at room temperature (RT). In addition to the enhanced pyroelectric response at RT, an enormous enhancement in the pyroelectric response (from 1750 to 90,900 μC m−2 K−1) was achieved at the depolarization temperature because of the sharp ferroelectric to antiferroelectric phase transition owing to coherent 180° domain switching. These results will motivate the development of a wide range of lead-free pyroelectric devices, such as thermal sensors and infra-red detectors.

The pyroelectric energy harvesting and storage performance around the ferroelectric/antiferroelectric transition in PNZST

The waste thermal/heat energy harvesting can contribute to more sustainable and efficient energy systems. The high energy harvesting and storage are indispensable with considering ferroelectric/antiferroelectric materials. In this work, Pb0.99Nb0.02[(Zr0.57Sn0.43)0.92Ti0.08]0.98O3 (PNZST) is studied for high energy density (harvesting and storage). The Olsen cycle is performed on the materials for direct thermal/waste heat to electrical energy conversion. A large energy harvesting density of 1.0 MJ/m3 per cycle was obtained at temperatures of 303 and 403 K, cycling the electric field between 1 and 9 kV/mm. An estimated high energy harvesting is a result of the polarization change due to the ferroelectric (rhombohedral) to antiferroelectric (tetragonal) phase transition. The high energy storage of 0.9 J/m3 and energy efficiency of 81% were obtained at 403 K under an electric field of 9 kV/mm. The results will enrich our understanding of PNZST materials that offer high-performance energy harvesting and storage-based applications. This work can also be helpful in improving energy harvesting density via phase transition behaviors.

Temperature-dependent Raman scattering and x-ray diffraction study of phase transitions in layered multiferroic CuCrP2S6

Functional van der Waals layered materials, which exhibit interesting phenomena such as magnetism and ferroelectricity, have been proposed for use in next-generation nanoscale devices and sensors. $\mathrm{CuCr}{\mathrm{P}}_{2}{\mathrm{S}}_{6}$ is a promising two-dimensional (2D) material that evinces multiferroic behavior where the $\mathrm{C}{\mathrm{u}}^{+}$ and $\mathrm{C}{\mathrm{r}}^{+3}$ cations are responsible for antiferroelectric and antiferromagnetic ordering, respectively. In this study, we use x-ray diffraction and Raman spectroscopy to map out these phase transitions in the range 70--400 K. The antiferroelectric phase transition is complex and shows a gradual transition to complete antipolar order with an intermediate quasiantipolar step. X-ray diffraction studies reveal evidence for negative thermal expansion across the antipolar phase transitions at \ensuremath{\sim}270 and \ensuremath{\sim}140 K. The latter of these is accompanied by a drastic reduction in rotational and translational mode frequencies of the anion groups in $\mathrm{CuCr}{\mathrm{P}}_{2}{\mathrm{S}}_{6}$. Our temperature-dependent structural data provide an important reference for subsequent research into this promising 2D multiferroic material.

Oxygen octahedral coupling mediated ferroelectric-antiferroelectric phase transition based on domain wall engineering

Exotic domain-wall phenomena make ferroelectrics the candidates for nanoelectronics. The local symmetry and structure anomalies at domain walls have raised interest in the unusual functionalities, such as domain wall chirality and conductivity. Especially, the spontaneous lattice distortion and symmetry breaking at domain walls activate them as the location of structural transformation. However, the routes to achieve ferroelectric-antiferroelectric phase transition via ferroelectric domain walls remain challenging, which are important to develop materials for energy storage and conversion. Here, we have observed stepwise antiferroelectric phase transition in strained pure BiFeO3 ultrathin films derived from ferroelectric domain walls. Aberration-corrected transmission electron microscopy observation reveals that the resultant phase transition is mediated by dense 180° domain walls via providing the antiparallel cation displacement, cooperating with the enhanced interfacial oxygen octahedral clamping. First-principles calculations further confirm the critical role of interfacial oxygen octahedral coupling during this transition. These findings report an alternative route for antiferroelectric phase transition. Besides, our results provide fresh insights into functionalities of ferroelectric domain walls and open a venue for developing energy-storage materials based on domain engineering.

Rich antiferroelectric phase diagram of antiferroelectric–ferroelectric superlattices: internal electric field- and interface induced phase transitions

We propose a thermodynamic model to the study the antiferroelectric (AFE) phase transitions in antiferroelectric–ferroelectric (AFE–FE) superlattices in which the coupling at the interface between two layers is mediated by local polarizations. Phase diagram of the AFE layer in term of the degree of interfacial effect λ and temperature T involving ferrielectric (FI) and ferroelectric (FE) phases is investigated. These two phases are stabilized by the interfacial effect and internal electric field. AFE thickness LAFE versus T phase diagram is also constructed. Intermediate regions of two-phase coexistence (IM) emerge in the λ–T and LAFE–T phase diagrams, if certain interface properties λ and layer thickness LAFE criteria are met. These IM regions are metastable states, which exist as a transition state between two phases. A tricritical point locates at the boundaries across the FI, IM and FE phases is found in the LAFE–T phase diagram. Competition among the internal electric field due to the electrostatic coupling, the FE ordering arises from the interfacial effect and the antiferroelectric ordering within the AFE layer giving rises to the rich AFE phase diagram.

Domain formation and phase transitions in the wurtzite-based heterovalent ternaries: a Landau theory analysis.

Characterizing the crystalline disorder properties of heterovalent ternary semiconductors continues to challenge solid-state theory. Here, a Landau theory is developed for the wurtzite-based ternary semiconductor ZnSnN2. It is shown that the symmetry properties of two nearly co-stable phases, with space groups Pmc21 and Pbn21, imply that a reconstructive phase transition is the source of crystal structure disorder via a mixture of phase domains. The site exchange defect, which consists of two adjacent antisite defects, is identified as the nucleation mechanism of the transition. A Landau potential based on the space-group symmetries of the Pmc21 and Pbn21 phases is constructed from the online databases in the ISOTROPY software suite and this potential is consistent with a system that undergoes a paraelectric to antiferroelectric phase transition. It is hypothesized that the low-temperature Pbn21 phase is antiferroelectric within the c-axis basal plane. The dipole arrangements within the Pbn21 basal plane yield a nonpolar spontaneous polarization and the electrical susceptibility derived from the Landau potential exhibits a singularity at the Néel temperature characteristic of antiferroelectric behavior. These results inform the study of disorder in the broad class of heterovalent ternary semiconductors, including those based on the zincblende structure, and open the door to the application of the ternaries in new technology spaces.