Ferroelectric Field Research Articles

Non-hydrostatic pressure induced α to β phase transition in group IV-VI Monochalcogenide GeSe

The family of group IV-VI monochalcogenides shows great potential for advanced applications in the fields of ferroelectrics, electronics and thermoelectrics. Here we report the direct observation of α to β...

Durable Photo-Pyroelectric Detection in a Diamine-Constructed Lead-Free Hybrid Perovskite Ferroelectric.

As a subcategory of pyroelectric materials, hybrid perovskite ferroelectrics possess substantial pyroelectric properties and exceptional light absorption characteristics, demonstrating significant potential in the photo-pyroelectric (PPE) detection field. Despite the significant advantages of hybrid perovskite ferroelectric materials for PPE detection, both the lead issue and the weak stability from van der Waals interactions in monoamines have hindered their further application. Here, 1D lead-free ferroelectric (BDA)SbBr5 (1, where BDA is 1,4-butanediammonium) is fabricated to achieve PPE detection. Compound 1 exhibits significant symmetry breaking attributed to the order-disorder transition of organic cations and octahedral distortions. Specifically, compound 1 enables broad-spectrum PPE detection from UV to near-infrared (377-980nm) and further realizes switchable pyroelectric current after polarization. More importantly, the stability of the pyroelectric current is preserved without degradation over three months, attributed to the hydrogen bonding interactions of butanediamide. Further theoretical calculations of compound 1 reveal a more negative energy of formation than its monoamine homologs (BA)2SbBr5 (where BA is n-butylammonium), which is evidence of its stability. These findings highlight 1 as a promising candidate for high-stability and environmentally friendly PPE wide-spectrum detection, representing a noteworthy advancement in the ferroelectric field.

The Integration of Two-Dimensional Materials and Ferroelectrics for Device Applications.

In recent years, there has been growing interest in functional devices based on two-dimensional (2D) materials, which possess exotic physical properties. With an ultrathin thickness, the optoelectrical and electrical properties of 2D materials can be effectively tuned by an external field, which has stimulated considerable scientific activities. Ferroelectric fields with a nonvolatile and electrically switchable feature have exhibited enormous potential in controlling the electronic and optoelectronic properties of 2D materials, leading to an extremely fertile area of research. Here, we review the 2D materials and relevant devices integrated with ferroelectricity. This review starts to introduce the background about the concerned themes, namely 2D materials and ferroelectrics, and then presents the fundamental mechanisms, tuning strategies, as well as recent progress of the ferroelectric effect on the optical and electrical properties of 2D materials. Subsequently, the latest developments of 2D material-based electronic and optoelectronic devices integrated with ferroelectricity are summarized. Finally, the future outlook and challenges of this exciting field are suggested.

Ferroelectricity enhanced photocatalysis in Bi2WO6 ultra-thin nanosheets

The fast recombination of photo-induced electrons and holes have long been an obstacle in hampering the photocatalytic reaction rate. To mediate this issue, various modulation methods have been explored, including rare metal doping, morphology control and heterojunction construction. However, these methods can only facilitate the surface charge transfer. In recent years, internal electric field modulation has been attracting more and more attention, due to its utility in promoting the bulk charge separation and transportation. Semiconductors with ferroelectricity, which can build directional internal field, is believed to possess enhanced photocatalysis efficiency. In this study, Bi2WO6 (BWO) ultra-thin nanosheets with ferroelectricity have been synthesized through hydrothermal process. The morphology and size can be controlled via surfactant addition. After corona poling, the ferroelectric field can be further enhanced, providing more efficient facilitation of carrier separation and higher reaction efficiency. The photodegradation efficiency toward Rhodamine B (RhB) and methyl orange (MO) are tested, and the polarized BWO-30 and BWO-40 can reach a 100 % degradation of RhB in 5 min, which is significantly faster than origin samples, and superior to most non-precious metal catalysts. This work proves the applicable of ferroelectric enhancement in BWO nanosheets, providing novel tactic for future catalysts design.

Statistical correlations of random polarization and electric depolarization fields in ferroelectrics

Statistical correlations of random polarization and electric depolarization fields in ferroelectrics

New optical soliton solutions of thin-film ferroelectric material equation via the complete discrimination system method

In this paper, our main aim is to construct the optical soliton solutions of the well-known thin-film ferroelectric material equation, which describes the propagation of polarization in thin-film materials. Because it has been found that solitary waves may be important for the propagation of polarization fields in ferroelectrics, we investigate its optical soliton solutions using the complete discrimination system technique in this study. As a result, the optical soliton solutions and various solutions are acquired, covering the elliptic double periodic function solution, Jacobian elliptic function solution etc. It appears that bright and singular waves can be propagated in thin-film ferroelectric materials. The richness of the solutions obtained will be conducive to further understand the whole picture of the dynamic behavior of wave propagation in thin-film material. Moreover, this research methods and results are efficacious and can be applied to the exploration of more complex phenomena. Finally, via giving some fixed parameter values, we plot 3D, 2D, density and contour graphs of some obtained solutions for presenting in visual form.

Topological phases in polar oxide nanostructures

Topology provides a framework for an understanding of emergent phenomena in various fields such as the appearance of new results in the field of ferroelectrics. A historical introduction and a primer on the concepts of topology are followed by a discussion of experimental and theoretical methods that elucidate the exotic textures that appear in polar oxide nanostructures and superlattices. The complex interplay of several fundamental processes occurring on different energy scales leads to ground states that compete with one another and have large and/or novel responses with respect to external stimuli.

Microstructure and dielectric properties of perovskite-structured high-entropy ceramics of Pb(Zr0.25Ti0.25Sn0.25Hf0.25)O3

A dielectric high-entropy ceramic with a composition of Pb(Zr0.25Ti0.25Sn0.25Hf0.25)O3 was designed through B-site doping, and then prepared by solid phase reaction method combined with conventional sintering in air for 3 h at 1200 °C, 1250 °C and 1300 °C, respectively. All the high-entropy ceramics of Pb(Zr0.25Ti0.25Sn0.25Hf0.25)O3 possess a perovskite structure with uniform elemental distribution and their average grain size falls within the range of 3.19–5.5 μm. For the sample sintered at 1250 °C, the dielectric loss is less than 0.07 in the testing frequency of 1 kHz∼1 MHz in 30–350 °C, and the dielectric constant reaches a peak of 14356 at about 270 °C at 1 kHz. At room temperature, the remnant polarization Pr reaches 28.8 μC/cm2. The results demonstrate that the high-entropy ceramic of Pb(Zr0.25Ti0.25Sn0.25Hf0.25)O3 has great potentials in the dielectric and ferroelectric field.

Systematic Errors of Electric Field Measurements in Ferroelectrics by Unit Cell Averaged Momentum Transfers in STEM.

When using the unit cell average of first moment data from four-dimensional scanning transmission electron microscopy (4D-STEM) to characterize ferroelectric materials, a variety of sources of systematic errors needs to be taken into account. In particular, these are the magnitude of the acceleration voltage, STEM probe semi-convergence angle, sample thickness, and sample tilt out of zone axis. Simulations show that a systematic error of calculated electric fields using the unit cell averaged momentum transfer originates from violation of point symmetry within the unit cells. Thus, values can easily exceed those of potential polarization-induced electric fields in ferroelectrics. Importantly, this systematic error produces deflection gradients between different domains seemingly representing measured fields. However, it could be shown that for PbZr0.2Ti0.8O3, many adjacent domains exhibit a relative crystallographic mistilt and in-plane rotation. The experimental results show that the method gives qualitative domain contrast. Comparison of the calculated electric field with the systematic error showed that the domain contrast of the unit cell averaged electric fields is mainly caused by dynamical scattering effects and the electric field plays only a minor role, if present at all.

Structural, dielectric, and leakage current analysis of ‘La’ doped BiMnO3

Multiferroic perovskites simultaneously exhibit ferroelectric, ferromagnetic, and/ antiferromagnetic ordering, as well as spontaneous polarization and magnetization controlled under magnetic and ferroelectric fields, simultaneously. There are many potential applications for multiferroic perovskites in the field of spintronics and magnetoelectric data storage. In the present investigation, we have synthesized and characterized the La-doped BiMnO3 ceramic material at high pressure and temperature by using solid state reaction route. The concentration of La into BiMnO3 at La site in the amount 0%, 2%, 4%, and 8% is fixed by the solid state reaction route and denoted by BML0, BML2, BML4 and BML8. Some impurity phases are observed by the powder X-ray diffraction analysis including the monoclinic structure for all compositions. Nevertheless, we encountered some difficulties while synthesizing BiMnO3 due to the volatile nature of Bi, antiferromagnetic behavior, large leakage current, etc. Enhanced dielectric properties are observed via the dielectric analysis. The reduction in the leakage current is observed with the La doping into BiMnO3.

Ground-state structures, electronic structure, transport properties and optical properties of Ca-based anti-Ruddlesden-Popper phase oxide perovskites

Anti-Ruddlesden-Popper (ARP) phase oxide perovskites ${\mathrm{Ca}}_{4}\mathrm{O}{A}_{2}$ $(A=\mathrm{P}, \mathrm{As}, \mathrm{Sb}, \mathrm{Bi})$ have recently attracted great interest in the field of ferroelectrics and thermoelectrics, whereas their optoelectronic application is limited by their indirect band gaps. In this work, we introduce $A$-site anion ordering in ${\mathrm{Ca}}_{4}\mathrm{O}{A}_{2}$ $(A=\mathrm{P}, \mathrm{As}, \mathrm{Sb}, \mathrm{Bi})$, and find that it induces an indirect-to-direct band gap transition. Using first-principles calculations, we study the ground-state structures, electronic structure, transport properties and optical properties of anion-ordered ARP phase oxide perovskites ${\mathrm{Ca}}_{4}\mathrm{O}A{A}^{\ensuremath{'}}$. Based on analyses of the lattice dynamics, the ground-state structures of ${\mathrm{Ca}}_{4}\mathrm{OAsSb}$ and ${\mathrm{Ca}}_{4}\mathrm{OAsBi}$ are identified in $P4/nmm$ symmetry and those of ${\mathrm{Ca}}_{4}\mathrm{OPSb}$ and ${\mathrm{Ca}}_{4}\mathrm{OPBi}$ are in the $I222$ symmetry. In contrast to the Ruddlesden-Popper (RP) phase oxide and halide counterparts, ${\mathrm{Ca}}_{4}\mathrm{O}A{A}^{\ensuremath{'}}$ $(A{A}^{\ensuremath{'}}=\mathrm{PSb}, \mathrm{PBi}, \mathrm{AsSb}, \mathrm{AsBi})$ show larger band dispersion along the out-of-plane direction, smaller band gaps and highly enhanced out-of-plane mobilities, which results from the short interlayer distances and the enhanced covalency of the pnictides. Although the out-of-plane mobilities of these $n=1$ ARP phase perovskites highly increase, the comparatively strong polar optical phonon scattering limits the further enhancement of their mobilities. Furthermore, compared to RP phase halide ${\mathrm{Cs}}_{2}{\mathrm{PbI}}_{2}{\mathrm{Cl}}_{2}$, ${\mathrm{Ca}}_{4}\mathrm{O}A{A}^{\ensuremath{'}}$ show strong optical absorption around the band edges, and their optical absorption coefficients can reach ${10}^{5}\phantom{\rule{0.28em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1}$ within the visible light region due to small band gaps. This study reveals that these ARP phase oxide perovskites exhibit the potential for optoelectronic applications.

Ferroelectric hybrid organic-inorganic perovskites and their structural and functional diversity.

Molecular ferroelectrics have gradually aroused great interest in both fundamental scientific research and technological applications because of their easy processing, light weight and mechanical flexibility. Hybrid organic-inorganic perovskite ferroelectrics (HOIPFs), as a class of molecule-based ferroelectrics, have diverse functionalities owing to their unique structure and have become a hot spot in molecular ferroelectrics research. Therefore, they are extremely attractive in the field of ferroelectrics. However, there seems to be a lack of systematic review of their design, performance and potential applications. Herein, we review the recent development of HOIPFs from lead-based, lead-free and metal-free perovskites, and outline the versatility of these ferroelectrics, including piezoelectricity for mechanical energy-harvesting and optoelectronic properties for photovoltaics and light detection. Furthermore, a perspective view of the challenges and future directions of HOIPFs is also highlighted.

Selectively constructing sandwich-like heterostructure of CdS/PbTiO3/TiO2 to improve visible-light photocatalytic H2 evolution

Fast migration and efficient spatial separation of photogenerated charges in photocatalytic materials are indispensable to efficient solar water splitting reactions. Here, we construct a three-phase heterostructure of CdS/PbTiO3/TiO2 by selectively depositing CdS and TiO2 at oppositely poled crystal facets of PbTiO3 using single-domain ferroelectric PbTiO3. The heterostructure has matching band edge alignments and strong interfacial connections at different moieties. The heterostructure combines the interfacial electrical and ferroelectric fields because of their peculiar microstructures, which provide a strong driving force throughout the whole bulk to separate photogenerated charges. Almost two orders of magnitude improvement of visible-light-driven photocatalytic H2 production has been realized in CdS/PbTiO3/TiO2 compared with bare PbTiO3/TiO2, showing the efficiency of charge separation in the heterostructure. The idea of combining ferroelectrics with potential light capture semiconductor provides a paradigm to accurately design charge migration pathways, bringing a step closer to efficient solar water splitting.

Effect of electric field on elastic properties of BaTiO3 single crystals: a micro-Brillouin scattering study

The analysis of local polar clusters formed by random fields in ferroelectrics is of technical and fundamental importance in understanding piezoelectricity. The temperature and electric field dependences of elastic properties and the ferroelectric phase transition have been investigated in (100)-oriented BaTiO3 single crystals by micro-Brillouin scattering. In the field cooling process, LA phonons are scattered by polar clusters. As a result, the LA phonon frequency increases as compared with that of the zero-field cooling process. Under the application of an external electric field along the [100] direction in the tetragonal ferroelectric phase, a complete 90° domain switching is accomplished. Under the electric field, abrupt changes in the frequency shift and FWHM of the LA phonons in the paraelectric cubic phase indicate the occurrence of a phase transition from the cubic to the tetragonal phase. An E–T phase diagram has been proposed from the field-induced phase transition.

A Multilevel Analytical Theory for Prediction of Ferroelectric Perovskite Oxide Properties from Composition.

Prediction of properties from composition is a fundamental goal of materials science that is particularly relevant for ferroelectric perovskite oxide solid solutions where compositional variation is a primary tool for material design. Design of ferroelectric oxide solid solutions has been guided by heuristics and first-principles and Landau-Ginzburg-Devonshire theoretical methods that become increasingly difficult to apply in ternary, quaternary, and quintary solid solutions. To address this problem, a multilevel model is developed for the prediction of the ferroelectric-to-paraelectric transition temperature (Tc ), coercive field (Ec ), and polarization (P) of PbTiO3 -derived ferroelectric solid solutions from composition. The characteristics of the materials at different length scales, starting at the level of the electronic structure and chemical bonding of the constituent ions and ending at the level of collective behavior, are analytically related by using ferroelectric domain walls and cationic off-center displacements as the key links between the different levels of the model. The obtained composition-structure-property relationships provide a unified quantitatively predictive theory for understanding PbTiO3 -derived solid solutions. Such a multilevel analytical modeling approach is likely to be generally applicable to different classes of ferroelectric perovskite oxides and to other functional properties, and to materials and properties beyond the field of ferroelectrics.

Pressure induced structural phase transition and piezochromism in photovoltaic sillen compounds PbBiO2X (X = Cl, Br & I)

Hydrostatic pressure is an effective and clean method that can give rise to the emergence of novel crystal structures and physical properties. Thus, hydrostatic pressure can be used for designing new functional materials. Sillen materials or PbBiO2X (X = Cl, Br & I) are a class of materials which have gained considerable interest in the field of ferroelectrics, photocatalysis, etc. In this work, we have used first principles methods to predict the crystal structure and phase of sillen materials at different pressure points from 0 to 50 GPa. It was then followed by the study of their structural, electronic and optical properties upon compression. Upon compression, the band gaps decreased within a particular phase and showed kinks on phase transitions. In the compressed states, the band gaps are in the suitable range to be used in the visible range of the spectrum for photovoltaic properties. Piezochromism is also reported upon compression as can been seen from the changes in the optical absorption spectra. This work should remove any confusion with regards to the responsible phase at different pressures, and the possible existence of new phases with the respective band gaps should pave the way for future experimental works on photocatalysis and other energy applications.

High-performance ReS2 photodetectors enhanced by a ferroelectric field and strain field.

Flexible optoelectronic devices have numerous applications in personal wearable devices, bionic detectors, and other systems. There is an urgent need for functional materials with appealing electrical and optoelectronic properties, stretchable electrodes with outstanding mechanical flexibility, and gate medium with flexibility and low power consumption. Two-dimensional transition metal dichalcogenides (TMDCs), a novel kind of widely studied optoelectrical material, have good flexibility for their ultrathin nature. P(VDF-TrFE) is a kind of organic material with good flexibility which has been proved to be a well-performing ferroelectric gate material for photodetectors. Herein, we directly fabricated a well-performing photodetector based on ReS2 and P(VDF-TrFE) on a flexible substrate. The device achieved a high responsivity of 11.3 A W−1 and a high detectivity of 1.7 × 1010 Jones from visible to near-infrared. Moreover, with strain modulation, the device's responsivity improved 2.6 times, while the detectivity improved 1.8 times. This research provides a prospect of flexible photodetectors in the near-infrared wavelength.

SnSe/SnS: Multifunctions Beyond Thermoelectricity

Miniaturization, lightweight and highly integration have gradually become the main trends in the development of modern science and technology. Two-dimensional (2D) SnSe/SnS-based materials have recently received widespread attention in the field of thermoelectricity because of the remarkable physical transport properties. However, the peculiar crystal structure also ensures that SnSe and SnS materials can meet the requirements of the miniaturized and highly integrated functional devices, which make them the most notable interdisciplinary hotpots. In this review, we initially analyzed the basic physical properties and outlined the important achievements in thermoelectric field of SnSe/SnS. With the development of preparation technology for thin-film materials and nanomaterials, SnSe/SnS has been successfully utilized in multiple fields, including photothermal, photoelectric and ferroelectric fields. We then elaborated the multifunctions in SnSe/SnS, such as solar cells, photodetectors, photocatalysis, etc. Eventually, some personal summaries and prospects are demonstrated, which might highlight the importance of multifunction and promote the potential applications of 2D materials including SnSe/SnS.

Effect of Buffer Layer Capacitance on the Electrical Characteristics of Ferroelectric Polymer Capacitors and Field Effect Transistors.

We demonstrated the effect of a buffer layer on the electrical characteristics of ferroelectric polymer capacitors and field-effect transistors. Various polymer materials with a dielectric constant between 2 and 42 were used to form buffer layers with a similar thicknesses, but with different capacitances. In order to evaluate the characteristics of the ferroelectrics with a buffer layer, the polarization–voltage characteristics of the capacitor, the transfer characteristics, and the retention characteristics of the transistors were investigated. As the capacitance of the buffer layer increased, high remnant polarization (Pr), high hysteresis, and long retention times were observed. Exceptionally, when poly(methylmethacrylate) and rigid poly(aryl ether) (poly(9,9-bis(4-hydroxyphenyl)fluorene-co-decafluorobiphenyl)) were used as the buffer layer, Pr had a value close to 0 in the dynamic measurement polarization–voltage (P–V) characteristic, but the quasi-static measurement transfer characteristic and the static measurement retention characteristic showed relatively high hysteresis and long retention times. Our study provides a scientific and technical basis for the design of ferroelectric memory and neuromorphic devices.

Observation of Transition from Ferroelasticity to Ferroelectricity by Solvent Selective Effect in Anilinium Bromide.

Organic ferroelectrics are highly desirable for their light weight, mechanical flexibility and biocompatibility. However, the rational design of organic ferroelectrics has always faced great challenges. Anilinium bromide (AB) has two structures reported in the Cambridge Crystallographic Data Centre, which might be an mmmF2/m type ferroelastic (AB-1). When we studied its ferroelasticity, we were surprised to discover that there was another crystal (AB-2) in H2 O besides this one, and they were very difficult to separate. By changing the solvent, we found that AB-1 crystals could be formed in ethanol, where ferroelastic domains were visualized by polarized light microscopy, and AB-2 crystals could be obtained from various crystallization solvents of methanol, isopropanol, N-butanol, acetonitrile, dimethyl sulfoxide, and N,N-dimethylformamide, which undergo a ferroelectric phase transition with mm2Fm, showing clear ferroelectricity in two phases. To our knowledge, the regulation of ferroelasticity to ferroelectricity by solvent selective effect is unprecedented in the field of ferroelectrics. This work reveals the important role of solvent effect in organic ferroelectrics.