The construction of organic-inorganic hybrid ferroelectric materials with larger, high-polarity guest molecules intercalated in kaolinite (K) faces difficulties in terms of synthesis and uncertainty of structure-property relationships. The purpose of the present study was to optimize the synthesis method and to determine the mechanism of ferroelectric behavior of kaolinite intercalated with p-aminobenzamide (PABA), with an eye to improving the design of intercalation methods and better utilization of clay-based ferroelectric materials. The K-PABA intercalation compound (chemical formula Al2Si2O5(OH)4∙(PABA)0.7) was synthesized in an autoclave and then characterized using X-ray diffraction (XRD), infrared spectroscopy (IR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The experimental results showed that PABA expanded the kaolinite interlayer from 7.2 Å to 14.5 Å, and the orientation of the PABA molecule was ~70° from the plane of the kaolinite layers. The amino group of the PABA molecule was close to the Si sheet. The presence of intermolecular hydrogen bonds between kaolinite and PABA and among PABA molecules caused macro polarization of K-PABA and dipole inversion under the external electric field, resulting in K-PABA ferroelectricity. Simulation calculations using the Cambridge Sequential Total Energy Package (CASTEP) and the ferroelectricity test revealed the optimized intercalation model and possible ferroelectric mechanism.

Over the past three years, my colleagues and I have embarked on an exciting journey into electric-field control of magnetism, parts of which we describe in this article. What we present to you is something that we believe is extremely exciting from both a fundamental science and applications perspective, and has the potential to revolutionize our world. Needless to say, this will require a lot of new innovations, both in the fundamental science arena as well as translating scientific discoveries into real applications. We hope this article will help spur more research in electric-field control of magnetism within the broad materials community.

Using ab initio simulation, we study a ferroelectric layer of a few nanometers made of hafnia (HfO2) under the influence of Si doping with TiN electrodes. We evaluate the orthorhombic phase of Pca21 symmetry, its ferroelectric switching and the incidence of doping with silicon. We show that the ferroelectric switching can involve a 90° characteristic angle with corresponding activation energy which is lowered by a factor three due to Si doping at 3% at. A full MFM (Metal-Ferroelectric-Metal) model is derived in order to simulate finite-size effects. This model is compatible with a reversal of a polar HfO2:Si with a (111) preferential orientation. Validity and usefulness of such a model are discussed for ferroelectric devices optimization.

By using systematic first-principles calculation, we found that AlTlO3 compound of LiNbO3 structure shows large piezoelectric constants e33 of 10.7 C/m2 and d33 of 56.7 pC/N. These piezoelectric constants are approximately six times larger than those of LiNbO3. AlTlO3 is predicted to be stabilized above 7 GPa. On the other hand, the calculated dielectric constant ε33 shows diverged behavior around 2 GPa. This result indicates that AlTlO3 can be quenchable. Decomposition of the predicted piezoelectric constant revealed that the large piezoelectricity of AlTlO3 originates from the Tl displacement in accordance with external perturbation, which drives the ferroelectric soft mode of the corresponding paraelectric phase. However, the energy difference between the ferroelectric and paraelectric phases was small, approximately 1 meV/f.u. These insights suggest that fluctuation between ferroelectric and paraelectric phases causes large piezoelectricity in AlTlO3.

Multifunctionality was created by coupling an electronic charge carrier transport with ionic conductivity or ferroelectricity in polarized liquid crystal phases. Liquid-crystalline perylene bisimide derivatives bearing cyclotetrasiloxane rings and triethylene oxide chains formed nanosegregated columnar structures which could conduct ions as well as electrons. The spin-coated thin films could be insolubilized by the exposure on acid vapors and display electrochromism. Phenylterthiophene derivatives bearing a chiral alkyl side chain exhibited a ferroelectric phase, in which a photovoltaic effect was caused by the interaction between photogenerated charge carriers with the internal electric field formed by the spontaneous polarization of the ferroelectric phase.

Piezoelectric ceramics generate strain through the intrinsic piezoelectric effect, the motion of ferroelectric domain walls, or through field-induced phase transitions. The enhanced piezoelectric properties observed in morphotropic solid solutions arise from several distinct, but interrelated, mechanisms associated with the near degeneration of the energy surface from cubic to spherical symmetry. The phenomenological theory of ferroelectricity is used to explain the thermodynamic origins of strain generation mechanisms in these solid solutions. The displacement of ferroelectric domain walls is an extrinsic contribution to the piezoelectric response that can be controlled by modifying the host material with small concentrations of dopants. The concept of “hardening” is introduced; hardening can be useful in applications where piezoelectric energy conversion and low energy loss are more important than large strain. The operative mechanisms of strain generation and energy conversion in technologically important lead-based and lead-free piezoelectric materials are summarized.

Sodium bismuth titanate (NBT) and its solid solutions with other ABO3 perovskites are of great interest for lead-free ferroelectric and piezoelectric applications. In this article, we provide an introduction to the complex structure of NBT, including atomic displacements and nanoscale defects. We also review poling effects and properties as well as NBT-ABO3 phase equilibria. The interesting relaxor properties, frequency dispersion in dielectric permittivity, and field-induced structural phase transitions of these systems are discussed. Finally, we describe other functional, mechanical, and electrical properties of NBT.

0.62[0.75(Pb(Mg1/3Nb2/3)O3)–0.25(Pb(Yb1/2Nb1/2)O3)]–0.38(PbTiO3) ceramics were successfully textured in [001] via the template grain growth method using 1–7 vol% platelike BaTiO3 (BT) templated (the Lotgering factor of 0.91 at 5 vol% BT). Dielectric spectra indicated a normal ferroelectric behavior without any frequency dispersion and no low-temperature phase transition. The chemically stable BT phase within the matrix gave rise to a composite effect and its relatively inferior properties affected the dielectric and electromechanical properties. The lower T C of the BT decreased the Curie temperature from 226 to 213 °C (with a depolarization temperature of 204 °C). Significantly higher levels of strain (0.33%), narrower hysteresis level (7.7%), higher piezoelectric strain coefficient (660 pm/V), and low-field (<5 kV/cm) piezoelectric strain coefficient (1340 pm/V) at 50 kV/cm were achieved at 5 vol% BT addition. These results are very promising for the fabrication of high performance transducer and actuator applications without severe temperature limitations.

This article provides a personal guided tour of multiferroic materials, from their early days as a theoretical curiosity, to their position today as a focus of worldwide research activity poised to impact technology. The article begins with the history of, and the answer to, the question of why so few magnetic ferroelectric multiferroics exist, then gives a survey of the mechanisms and materials that support such multiferroicity. After discussing the tremendous progress that has been made in the magnetoelectric control of magnetic properties using an electric field, some unusual applications of multiferroics in high-energy physics and cosmology are outlined. Finally, the most interesting open questions and future research directions are addressed.

The rapid growth of scientific publications necessitates new methods to understand the direction of scientific research within fields of study, ascertain the importance of particular groups, authors, or institutions, compute metrics that can determine the importance (centrality) of particular seminal papers, and provide insight into the social (collaboration) networks that are present. We present one such method based on analysis of citation networks, using the freely available CiteSpace Program. We use citation network analysis on three examples, including a single material that has been widely explored in the last decade (BiFeO3), two small subfields with a minimal number of authors (flexoelectricity and Kitaev physics), and a much wider field with thousands of publications pertaining to a single technique (scanning tunneling microscopy). Interpretation of the analysis and key insights into the fields, such as whether the fields are experiencing resurgence or stagnation, are discussed, and author or collaboration networks that are prominent are determined. Such methods represent a paradigm shift in our way of dealing with the large volume of scientific publications and could change the way literature searches and reviews are conducted, as well as how the impact of specific work is assessed.

Pb0.88 Ln 0.08TiO3 ferroelectric system, where Ln = La, Sm, Eu, and Dy, has been characterized using Scanning Electron Microscopy, Raman spectroscopy, and X-ray diffraction experiments. Softening of the lowest transverse optical phonon mode E (1TO) was evaluated as a function of the rare earths’ ionic radius suggesting partial occupation of lanthanide ions at the A and B sites of the perovskite structure. Using Rietveld refinements, it has been established a higher incorporation of Ln3+ ions into the A sites of the perovskite structure than that of the B sites for the studied ceramics. The occupation at B sites increases slightly with the decreases of the ionic radii of the lanthanides.

We fabricated ferroelectric (Pb,La)(Zr,Ti)O3 (PLZT) capacitors withSn:In2O3 (ITO) or Pt top electrodes and investigatedthe ferroelectric properties of these PLZT capacitors. The shape ofpolarization–voltage hysteresis loops was essentially unchanged andthe decrease in the remnant polarization of the ITO/PLZT/Pt capacitors wassmaller than that of the Pt/PLZT/Pt capacitors after annealing with 3%D2 (in N2) at 200°C and 1 Torr(i.e., FGAD). Time of flightsecondary mass spectrometry revealed that the D atoms were incorporated into thePLZT film of the Pt/PLZT/Pt capacitors after 3% D2 annealing,resulting in a decrease in the ferroelectric properties. In comparison, no D ionsignal was detected in the PLZT film after FGAD for ITO/PLZT/Ptcapacitors.

YCrO3 (YCO) is known to be a multiferroic with orthorhombic,Pnma, structure with center of inversion. However, thelocal structural inhomogeneity in this compound is believed to give rise toferroelectric behavior. In this study we explore high temperature Ramaninvestigations of YCO and observed that one of its Raman mode B3g (3)(CrO6 Octahedral tilt mode) softens around the structural phasetransition which could be the origin of ferroelectric nature in YCO. Inaddition, we substitute bismuth (Bi) in YCO to understand the structuraldistortions that lead to local structural inhomogeneity. Besides B3g(3) mode softening with composition and high temperature studies inY1-xBixCrO3 the study reveals thestructural distortions and the structural tunability Bi offers in suchsystems.

The effect of Dy-doping on the dielectric nonlinearity was investigated in Mn and V-doped BaTiO3 multilayer ceramic capacitors under the same grain size condition, which was described by the Preisach model utilizing the first order reversal curve (FORC) distribution. The dielectric constants in both low and high field region could be enhanced by the Dy-doping, and it was associated with the increase of both reversible and irreversible FORC distributions near zero bias, whereas there was little variation in the saturation polarization that scales to the magnitude of spontaneous polarization. These results demonstrate that both reversible and irreversible domain wall motions are enhanced by Dy-donor incorporation in BaTiO3 resulting in softening of the dielectrics and increase of dielectric constants, which is supposed to be caused by the decrease of the pinning sources such as defect dipoles formed by the oxygen vacancies and their interaction with the domain walls.

We fabricated ferroelectric (Pb,La)(Zr,Ti)O3 (PLZT) capacitors with Sn:In2O3 (ITO) top electrodes using chemical solution deposition. Then, the effects of a thin conductive ITO buffer layer between the Pt bottom electrode and PLZT thin film were investigated in combination with top electrode (ITO/PLZT/ITO/Pt). The H2 degradation resistance of ITO/PLZT/ITO/Pt capacitors with a 3- and 28-nm-thick buffer layer was improved to 78 and 85%, respectively, from 60% without a buffer layer. The time-of-flight secondary ion mass spectrometry profiles indicated the intensity of H ion increased after 45 min forming gas (3% H2/balance N2) annealing.

A generalized route encompassing a facile hybrid physical/chemical approach is reported for fabricating size and shape selective nanowires of technologically important ferroelectric perovskite oxides (Pb(Zr0.52Ti0.48)O3 (PZT) and Pb-free ZnSnO3) on industrially feasible large-area substrates. The approaches involve depositing nano-seed layers (50 - 100 nm in thickness) of the desired materials (Ti for PZT and ZnO for ZnSnO3) by pulsed laser deposition and RF sputtering techniques followed by oriented growth of nanowire arrays of these materials by solvothermal processes by varying solvent compositions and ratios. Similar crystal symmetry between the seed-layers facilitated the growth of well-aligned nanowire arrays of the targeted materials homogeneously on the substrates with a high packing density. Measurements of the electronic (field-emission), and ferroelectric properties of the materials are performed and discussed in terms of understanding their potential for future technological applications. The facile, low-cost method for fabricating high quality nanowires may expand the outreach of probes for understanding the structure-property relations in other perovskite materials.

We report the measurements of ferroelectricity in LiNbO3 (LN)-type ZnSnO3 /ZnO nanocomposite thick films deposited on Pt-Si substrates using a novel combined chemical/physical technique. Phase-pure LN-type ZnSnO3 nanorods (NRs) were first synthesized using a low temperature solvothermal process and characterized in detail using X-ray diffraction, electron microscopy and Raman spectroscopy. The prototype device for polarization measurements was fabricated by depositing the as-prepared LN-type ZnSnO3 NRs onto conducting Pt-Si substrates (also served as bottom electrodes). A dielectric filler-layer of polycrystalline ZnO was deposited on top using pulsed laser deposition to fabricate LN-type ZnSnO3 /ZnO nanocomposite films. Polarization measurements of the Pt/ZnSnO3+ZnO/Pt nanocomposite capacitors at 300K showed indication of polarization switching in the hysteresis loops with a remanent polarization (Pr) of 13 μC/cm2 at a low applied voltage of 8 V. The work provides information on the coherent design of future FE memory devices based on the emerging non-toxic Pb-free material LN-ZnSnO3.

Ultrathin ferroelectric heterostructures (SrTiO3/BaTiO3/BaRuO3/SrRuO3) were studied by scanning transmission electron microscopy (STEM) in terms of structural distortions and atomic displacements. The TiO2-termination at the top interface of the BaTiO3 layer was changed into a BaO-termination by adding an additional BaRuO3 layer. High-angle annular dark-field (HAADF) imaging by aberration-corrected STEM revealed that an artificially introduced BaO-termination can be achieved by this interface engineering. By using fast sequential imaging and frame-by-frame drift correction, the effect of the specimen drift was significantly reduced and the signal-to-noise ratio of the HAADF images was improved. Thus, a quantitative analysis of the HAADF images was feasible, and an in-plane and out-of-plane lattice spacing of the BaTiO3 layer of 3.90 and 4.22 Å were determined. A 25 pm shift of the Ti columns from the center of the unit cell of BaTiO3 along the c-axis was observed. By spatially resolved electron energy-loss spectroscopy studies, a reduction of the crystal field splitting (CFS, ΔL3=1.93 eV) and an asymmetric broadening of the eg peak were observed in the BaTiO3 film. These results verify the presence of a ferroelectric polarization in the ultrathin BaTiO3 film.

New strategies for materials fabrication are of fundamental importance in the advancement of science and technology. Nanocrystals, especially with an anisotropic shape such as cubic, are candidates for building blocks for new bottom-up approaches to materials assembly, yielding a functional architecture. Such materials also receive attention because of their intrinsic size-dependent properties and resulting applications. Here, we report synthesis and characteristics of BaTiO3 and SrTiO3 nanocubes and the ordered assemblies as ferroelectric supracrystals. BaTiO3 and SrTiO3 nanocubes with narrow size distributions were obtained in an aqueous process. BaTiO3 films made up of ordered nanocube assemblies were fabricated on various substrates by evaporation-induced self-assembly method. Regardless of the substrate, the nanocubes exhibited {100} orientations and a high degree of face-to-face ordering, which remained even after heat treatment at 850 °C. Piezoresponse force microscopy was carried out on the supracrsytal films to obtain plots of the d33 piezoelectric coefficient against the poling field, and ferroelectric hysteresis curves were shown.

A personal view of ferroelectrics and multiferroics research is given with suggestions for future work, emphasizing nano-dynamics.