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MACHINE LEARNING PREDICTS STRESS For the first time, scientists used machine learning to predict stress in copper at the atomic scale. Until now, predicting grain boundary stresses responsible for fracture [...]

Materials exhibiting a spontaneous electrical polarization (1,2) that can be switched easily between antiparallel orientations are of potential value for sensors, photonics and energy-efficient memories. In this context, organic ferroelectrics (3,4) are of particular interest because they promise to be lightweight, inexpensive and easily processed into devices. A recently identified family of organic ferroelectric structures is based on intermolecular charge transfer, where donor and acceptor molecules co-crystallize in an alternating fashion known as a mixed stack (5-8): in the crystalline lattice, a collective transfer of electrons from donor to acceptor molecules results in the formation of dipoles that can be realigned by an external field as molecules switch partners in the mixed stack. Although mixed stacks have been investigated extensively, only three systems are known (9,10) to show ferroelectric switching, all below 71 kelvin. Here we describe supra-molecular charge-transfer networks that undergo ferroelectric polarization switching with a ferroelectric Curie temperature above room temperature. These polar and switchable systems utilize a structural synergy between a hydrogen-bonded network and charge-transfer complexation of donor and acceptor molecules in a mixed stack. This supramolecular motif could help guide the development of other functional organic systems that can switch polarization under the influence of electric fields at ambient temperatures., Ordered networks of electron donors and acceptors are good candidates for organic ferroelectrics because of the possible long-range orientation of their charge-transfer dipoles. The canonical electron donor-acceptor systems--the mixed-stack tetrathiafulvalene [...]

An electrical analogue of the magnetic-skyrmion bubble -- a swirling arrangement of magnetic moments -- has been unveiled in an artificially layered oxide material, raising prospects of new physics and applications. Observation of an exotic polarization pattern., Author(s): Pavlo Zubko Author Affiliations: Electrifying skyrmion bubbles Like a pesky cowlick that can't be tamed no matter how much you threaten it with a comb, tiny whorls of magnetic [...]

The experimental results on laser beam guiding by a self-tightening lattice photo induced in a strontium barium niobate (SBN) photorefractive crystal is reported. The gradual transformation of the optical lattice into array of weakly coupled ones revealed significant role of induced modulation instability in the strong laser beam guiding.

The hysteresis loop formation mechanisms are analyzed in piezoresponse force microscopy (PFM) and a theoretical framework is developed for interpreting the PFM hysteresis measurements. Green's function theory is used for establishing the relationships between domain parameters and PFM signal.

Raman spectroscopy and x-ray diffraction are used for examining the domain structure and residual stress evolution with film thickness and of phase transition in c/a epitaxial PbTi[O.sub.3]/LaAl[O.sub.3] thin films. Findings reveal that the films were under tensile residual stress in the film plane.

A constant voltage driving method was used for examining the high-power piezoelectric characteristics in (001) oriented ceramics of bismuth layer structured ferroelectrics (BLSF), Sr[Bi.sub.2][Nb.sub.2][O.sub.9] (SBN), [(Bi,La).sub.4][Ti.sub.3][O.sub.12] (BLT) and Ca[Bi.sub.4][Ti.sub.4][O.sub.15] (CBT). Constant resonance frequencies were observed in the SBN and CBT.

The phase-transition temperatures and piezoelectric properties of ([Bi.sub.1/2][Na.sub.1/2])Ti[O.sub.3]-([Bi.sub.1/2][Li.sub.1/2])Ti[O.sub.3]-([Bi.sub.1/2][K.sub.1/2])Ti[O.sub.3] 9BNLKT100y-100z) ceramics are examined. Findings reveal the effectiveness of a small amount of Li-substitution for increasing the depolarization temperature of BNLKT4-100z from 185 degree Celsius to 221 degree Celsius at the rhombohedral composition.

The motion of domain walls is critical to many applications involving ferroelectric materials, such as fast high-density non-volatile random access memory (1). In memories of this sort, storing a data [...]

The evolution of non-spontaneous, high permittivity symmetry axis processing large piezoelectric activity in the relaxor lead magnesium niobate-ferroelectric lead titanate is presented.

X-ray photoemission spectroscopy (XPS) is used to evaluate the nature of defects in polycrystalline [Bi.sub.4-x][La.sub.x][Ti.sub.3][O.sub.12] (BLT) thin films. The XPS data has shown a nominal valence state of bismuth lower than 3 and Ti cations are found to be in the 4 state.

High-resolution piezoresponse force microscopy is used to investigate the nanoscale kinetics of ferroelectric domain wall motion in polycrystalline ferroelectric thin films. The kinetic model has predicted the wall velocity to go through changing maxima as a function of time during polarization relaxation process.

A thermodynamic theory of intrinsic finite-size effect model for single domain, mechanically free, and surface charge compensated PbTi[O.sub.3] (PT) nanocrystals with no depolarization fields, undergoing a first-order tetragonal -> cubic ferrodistortive phase transition is presented. Based on the results it is inferred that the reduction in the extent of dipolar ordering manifests itself as a size-driven ferroelectric -> paraelectric phase transition.

A scatheless visualization study was conducted to demonstrate that the engineered and spontaneous domains of lithium niobate (LiNb[O.sub.3]) crystal could be delineated by means of the nanoparticle decoration. The decoration technique is effective, easily operated, nondestructive for sample, noninvasive for human body and is suitable for the domain mapping of oxide ferroelectric crystals.

The piezoresponse force microscopy was used to carry out high-resolution study of polar structures on the 0.9Pb([Mg.sub.1/3][Nb.sub.2/3])[O.sub.3]-0.1PbTi[O.sub.3] (0.9PMN-0.1PT) single crystals. A complex pattern of nanosized polar regions (nanodomains) was observed above the temperature of the structural phase transition which is attributed to a peculiar transient state between relaxor and ferroelectric, developed near the crystal's surface.

The effect of x-ray irradiation on polarization switching properties of a glycine phosphite (GPI) single crystal is studied using the Merz technique. It is found that x-ray irradiation causes an increase in the threshold field below which switching does not occur, a linear dependence with irradiation time and an increase in domain wall mobility due to the reduction in the switchable sample volume as a result of the accumulation of a large number of radiation induced defects.

Combinatorial approach for discovering novel functional materials in the huge diversity of chemical composition and processing conditions has become more important for breakthrough in thin film electronic and energy-conversion devices. The efficiency of combinatorial method depends on the preparation of a reliable high-density composition thin-film library. The physico-chemical properties of each sample on the library should be similar to those of the corresponding samples prepared by one-by-one conventional methods. We successfully developed the combinatorial liquid source misted chemical deposition (LSMCD) method and demonstrated its validity in screening the chemical composition of [Bi.sub.3.75][La.sub.x][Ce.sub.0.25[right arrow]x][Ti.sub.3][O.sub.12] (BLCT) for high remanent polarization (Pr). LSMCD is a cheap promising combinatorial screening tool. It can control the composition up to ppm level and produce homogeneous multicomponent library. LSMCD method allows us to prepare BLCT thin-film library at the variation of 0.4 mol% of La. Maximum 2Pr is 35 [micro]/[cm.sup.-2] at x = 0.21. The intensity of (117) XRD peak is quantitatively related to 2Pr. Newly developed scanning piezoelectric deformation measurement for nano-sized samples using scanning probe microscope (SPM) is also found out to be reliable for determining the relative ranking of Pr value rapidly. BLCT thin film array | microbeam x-ray diffraction | scanning probe microscope

First-principles-based approach is used to determine the ferroelectric pattern in Pb[Zr.sub.0.5][TI.sub.0.5][O.sub.3] ultrathin film. A polarization vortex loop is induced under a local external field and the polarizations in the center of the field region are antiparallel with the field, which are helpful in manipulating the nanostructure in the ultrathin film.

The retention loss behaviors of dot domains and square domains with sizes of 1 and 25 mu[m.sup.2] are observed via a PFM image. This retention loss phenomenon of the domain reversed using an AFM tip is closely related to the shape of the c/c domain wall and the strainpolarization coupling effect of the reversed domain.

The x-ray diffraction, atomic force microscopy and transmission electron microscopy are used to study the microstructure and surface morphology of the multilayer stacks. The analysis shows that the ferroelectric films are polycrystalline textured with a columnar structure where the grain size is 50-100 nm.

High throughput method is described which is applicable to the development of ferroelectric thin films. The chemical solution deposition techniques containing 90 samples are used to prepare thin film libraries for an automated synthesis route.

The phenomenological Landau-Ginzburg-Devonshire theory is used to numerically investigate the effects of space charges on hysteresis loops and field distributions in ferroelectrics. A method is proposed to help in identifying fully depleted films from temperature dependent capacitance and hysteresis measurements.

Different fatigue states of a soft composition of bulk ferroelectric lead zirconate titanate are characterized by measurement of the nonlinearity of domain wall motion. It is showed that the dielectric as well as the nonlinear response of a ferroelectric bulk material change significantly upon fatigue.

Direct spectroscopic evidence of field-induced solid-state chain conformation transformation in a ferroelectric relaxor P(VDF-THFE-CFE) terpolymer is described. It is demonstrated that high electric field can convert part of the nearly nonpolar TGTG' chain into polar T[(sub m)(greater than)]4 and T(sub 3)G conformations in the ferroelectric relaxor P(VDF-THFE-CFE) terpolymer.

The influence of the thickness of polyvinyl alcohol alignment layer on azimuthal anchoring of ferroelectric liquid crystals (FLC) was investigated by measuring the azimuthal angle of the chevron C2 structure. It is found that azimuthal remains unchanged with increasing thickness of the FLC layer while anchoring is constant.

The analysis of the three-dimensional polymer network distribution inside the polymer-stabilized ferroelectric liquid-crystal layer is presented based on the laser scanning fluorescence confocal microscopy and a fluorescent dye tagging of the polymer. The studies of polymer-stabilized ferroelectric liquid-crystal structures are focused on the comparison of the influence of polymer network in case that the polymerization is initiated in the chevron as well as in the quasibookshelf liquid-crystal molecular orientation.

Twin-free epitaxial cubic (111) praseodymium sesquioxide films were prepared on Si(111) by hexagonal-to-cubic phase transition and synchrotron radiation grazing incidence X-ray diffraction and transmission electron microscopy were applied to characterize the phase transition and the film structure. Transmission electron microscopy shows that the phase transition is accompanied by an interface reaction at the oxide/Si(111) boundary.

Abstract: This study gives a detailed account of calculation of the bulk ferroelectric (FE) oscillatory dynamical system switching for first and second-order phase transition, respectively. All the formalism is delineated [...]

The first example of ferroelectrically switchable fluid columnar liquid crystalline compounds generated by achiral molecules is discussed. It was found that it is important to reduce the intercolumnar dipole-dipole interaction for realization of ferroelectric columnar liquid crystals.

The structural and thermal properties of potassium nitrate polyvinylidene fluoride composite films are studied. The capacitance-voltage characteristics exhibit strong hysteresis with pronounced peaks and some asymmetry.

Temperature and field dependent investigations of the longitudinal electromechanical properties of [001]- and [110]- oriented 0.955Pb (Zn(sub 1/3)Nb(sub 2/3))O(sub 3)-0.045PbTiO(sub 3) single crystal are performed. Electromechanical equivalence was found between [001] and [110] orientations in the ferroelectric rhombohedral Fe(sub r) phase region, but not in the ferroelectric tetragonal Fe(sub t).

The design, fabrication, and characterization of a 112 channel, 5 MHz, two-dimensional (2-D) array transducer constructed on a six layer flexible polyimide inter-connect circuit is described. The images showing the manipulation of a separate electrophysiological catheter into the coronary sinus is presented.

The variation of the electromechanical coupling and the quality factor of the resonators, for both the longitudinal and the shear modes as a function of the degree of film texture is studied. The film growth is in the competitive growth mode, thus enhancing column growth along the mean deposition flux.

High frequency, thickness mode resonators were fabricated using a 7-mu m piezoelectric transducer (PZT) thick film that was produced using a modified composite ceramic sol-gel process. Sol-gel derived ZrO(sub 2) was required as a diffusion barrier layer when using SiO(sub 2) as the each stop layer. The model showed that the PZT thick film has an e(sub 33) coefficient of 9 C.m(super -2).

The influence of finite aperture and frequency response of piezoelectric ultrasonic hydrophone probes on the free-field pulse intensity integral (PII) and mechanical index (MI) was investigated using a comprehensive acoustic wave propagation model. The model developed was capable of predicting the true pressure-time waveforms at virtually any point in the field.

A novel temperature compensated crystal oscillator - analog memory compensated crystal oscillator (AMCXO), a microcomputer compensated crystal oscillator (MCXO) based on an analogue approach is introduced. The performance between MCXO and AMCXO is compared and the necessity of developing the AMCXO is analyzed.

The behavior of a low molecular mass organosiloxane ferroelectric liquid crystal at the air-water interface is studied. The data obtained from Langmuir isotherms, surface potential measurements and Brewster angle microscopy are discussed.

The Samarium-modified, lead titanate ceramics with a composition of (Pb0.67Ca0.15Sr0.06Sm0.08) (Ti0.98Mn0.02) O3 are prepared by conventional mixed-oxide method. The piezoelectric and dielectric properties are measured, which showed that the samples with zero temperature coefficient still keep high-thickness, electromechanical coupling coefficient, kt (>0.55), and small planar electromechanical coupling coefficient, kp.

This article investigates the effect of free space charges on hysteresis-loop measurement of compositionally graded ferroelectrics and found that they are quite likely to be responsible for the polarization offsets observed in experiments. All the results of the experiment suggest that time-dependent space-charge-limited conduction is possible origin of the polarization offsets observed in compositionally graded ferroelectrics.

In this article, a ferroelectric capacitor is characterized by an experimental Preisach density, determined by first order reversal curves method. It is experimentally shown that this density, does not allow a complete model of the ferroelectrical behavior. Considering the domain wall phenomenon, an extension of the Preisach assumptions is suggested.

The optical convergent-beam technique has been used to study the director alignment in the three stable states of an anticlinic antiferroelectric liquid crystal cell. The biaxiality of the antiferroelectric state has been measured, uniaxial indices, the cone angle, and layer tilt has been determined for the ferroelectric state.

Characteristics of a p iezoelectric t ransducer ( PZT) thin film actuator are examined and reported.

The circuit equivalent of the Landau-Khalatnikov model of ferroelectric hysteresis is described and discussed.

Pyroelectric IR detectors, fabricated using polyvinylidene fluoride/lead titanate thin films, are described and discussed.

A numerical study has been carried out to understand the influences of barrier arrangements on the discharge characteristics of dielectric barrier discharge (DBD). A 1.5-dimensional (1.5-D) modeling is considered in the arrangements of bare, single-barrier, and double-barrier electrodes while a two-dimensional (2-D) approach is employed in a configuration of ferroelectric packed discharge (FPD). Numerical simulations show that the evolution of microdischarges in DBD occurs sequentially in the three distinctive phases of avalanche, streamer, and decay, and that the dielectric barriers make streamer discharges stabilized and sustained in lowered electric fields without transition to spark compared with no barrier case. Especially, the highly nonuniform strong electric field effect created by the pellets appears to be formed in FPD, which enables the flue gas cleaning to be expected to enhance the decomposition efficiency. Index Terms--Barrier arrangement effect, dielectric barrier discharge (DBD), ferroelectric packed discharge (FPD), numerical modeling.

The frequency interference between two mesa-shaped quartz crystal microbalances is examined, using Mindlin's theory.

Suraface acoustic wave (SAW) and acousto-optic (AO) properties of potassium niobate (KNbO[subscript 4]) are investigated and discussed.

The resonance frequency-temperature characteristics, as well as other selected properties, of GaPO[subscript 4] rotated Y-cut resonators are described and discussed.