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A large amount of economic and financial news is now accessible through various news websites and social media platforms. Categorizing them into appropriate categories can be advantageous for various tasks, such as sentiment analysis and news-based market prediction. Unfortunately, news headlines categories may contain ambiguities due to the subjective nature of label assignment by authors or publishers. Consequently, achieving precise classification of news can be time-consuming and still reliant on human expertise. To tackle this challenging task, we proposed a hybrid approach to enhance the performance of economic and financial news classification. This approach combines baseline classifiers with a novel method called the Category Associated Feature Set (CAFS) classifier. CAFS transforms text input from the lexicon-space into the entity-space and discovers associations between entities and classes, akin to association rule learning. Experimental results on three datasets demonstrated that the proposed method is comparable to existing approaches and exhibits a significant improvement in the classification results for out-of-domain datasets. Additionally, employing CAFS in tandem with the existing text classification baselines can provide a general categorizer for distinguishing news categories across various sources without the need for extensive fine-tuning of the parameters associated with those classification baselines. This confirms that utilizing CAFS in a hybrid approach is appropriate and suitable for economic and financial news classification. [ABSTRACT FROM AUTHOR]

In this study, the effects of Cl and Br surface doping on the surfaces' structural stability of CH3NH3PbI3 (MAPbI3) perovskite have been investigated using the density functional theory. Its aim is to pursue how to stabilize a flat surfaces structure (no vacancy) of the MAPbI3 perovskite in overcoming its chemical instability. In this calculation, the (001) texture of the MAPbI3 perovskite surface was modeled as a prototype. The 216-atom and 264-atom supercells were employed to imitate the Lead Iodide (PbI2)- and Methylammonium Iodine (MAI)-terminated surfaces, respectively. It was found that doping of either Cl or Br atoms on perovskite surfaces enhances the energies required for releasing PbI2 and MAI molecules from the surfaces, causing vacancies on the surfaces. This is owed to the binding energies between the Cl and Br dopants and their surrounding atoms on the surfaces being stronger than those created by the Iodine atom. This implies that the formation of surface vacancies—which causes perovskite's degradation—can be prevented by Cl and Br surface doping. The obtained results elucidate the capability of Cl and Br dopants on surface stabilization, describing why one should incorporate Cl/Br into MAPbI3 to overcome instability issues and enhance the efficiency of the MAPbI3-based perovskite solar cell. [ABSTRACT FROM AUTHOR]

Local structure of lead zinc niobate (PZN) ceramic, synthesized via B-site oxide precursor route in atmospheric pressure, was investigated using synchrotron x-ray absorption spectroscopy (XAS) technique. The x-ray absorption near-edge structure (XANES) simulation was first carried out. The XANES simulation results indicate that the PZN ceramic is in pyrochlore phase having Zn2+ substituted on Nb5+ site. Afterwards, the extended x-ray absorption fine structure (EXAFS) analysis was performed to extract the bond length information between Zn2+ and its neighboring atoms. From the EXAFS fitting, the bond length between Zn2+ and Pb2+ in the pyrochlore phase was found to be longer than the previously reported bond length in the perovskite phase. Further, with the radial distribution information of Zn2+'s neighboring atoms, the formation energies along the precursor-to-pyrochlore and precursor-to-perovskite reaction paths were calculated using the density functional theory (DFT). The calculated results show that the formation energy of the perovskite phase is noticeably higher than that of the pyrochlore phase, which is influenced by the presence of energetic Pb2+ lone pair, as the perovskite phase has shorter Zn2+ to Pb2+ bonding. This therefore suggests the steric hindrance of Pb2+ lone pair and the mutual interactions between Pb2+ lone pair and Zn2+ are main causes of the instability of lead zinc niobate in the perovskite structure and confirm the efficacy of XAS and DFT analysis in revealing local structural details of complex pyrochlore materials. [ABSTRACT FROM AUTHOR]

Effects of compressive stress on the ferroelectric properties of Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN-PT) ceramics were investigated. The ceramics with the formula (1-x)Pb(Mg1/3Nb2/3)O3-(x)PbTiO3 or (1-x)PMN-(x)PT (x=0.1–0.5) were prepared by a conventional mixed-oxide method. Dense perovskite-phase PMN-PT ceramics with a uniform microstructure were obtained. The ferroelectric properties were measured under compressive stress (0–75 MPa) using a homebuilt compressometer in conjunction with a modified Sawyer–Tower circuit. The experimental results revealed that the superimposed compression stress significantly reduced both the dissipation energy and the polarizations of the near morphotropic phase boundary compositions, i.e., 0.8PMN-0.2PT, 0.7PMN-0.3PT, and 0.6PMN-0.4PT, while the stress influence was much less in other compositions. On the contrary, the applied compressive stress showed little or no influence on the coercive field. These results were interpreted through the non-180° ferroelastic domain switching processes and the stress induced decrease in the switchable part of domains. [ABSTRACT FROM AUTHOR]

The dielectric and ferroelectric properties of (1-x)Pb(Mg1/3Nb2/3)O3-(x)PbTiO3 or (1-x)PMN-(x)PT (x=0.1–0.4) ceramics were measured under compressive stress applied perpendicular to the electric field. For the dielectric properties, the experimental results revealed that the superimposed perpendicular compression stress reduced the dielectric constant but increased the dielectric loss tangent of all the compositions. On the other hand, for the ferroelectric properties the applied stress noticeably enhanced the dissipation energy, the polarizations, and the coercive field of all the compositions. These results were interpreted through the non-180° ferroelastic domain switching processes, the stress clamping of domain walls, the deaging mechanism, and the stress induced enhancement in the switchable part of spontaneous polarization. More importantly, the influences of the stress applied in the perpendicular direction to the electric field were generally opposite to those of the parallel stress. [ABSTRACT FROM AUTHOR]

The study of ZnO nanostructures is interested because the various types of nanostructures can be easily fabricated. However, the magnetic ground state of Ni-doped ZnO nanostructures can either be ferromagnetic or antiferromagnetic. Therefore, this work used DFT calculation to investigate the ZnO in low dimensional structures in both polar (0001) surfaces and non-polar () surfaces. The two Ni atoms were substituted on the Zn sites. The results show that the polar (0001) surfaces is more stable than the non-polar () surfaces. The energy differences between ferromagnetic states and antiferromagnetic state indicate that the ground states are ferromagnetic except only when the Ni atoms substitute on the slab surface in ZnO polar (0001) surfaces. The total magnetic moments of about 4 µB are found to be contributed by the Ni-3d states in both polar and non-polar surfaces, and the half-metallic behavior is also predicted in the ZnO non-polar () surfaces. [ABSTRACT FROM AUTHOR]

Density functional theory was used to inspect the structural properties and morphotropic phase boundaries (MPBs) of Ag1-xKxNbO3 (AKN) solid solutions. Structural properties of pristine AgNbO3 in Pbcm and Pmc21 phases were firstly investigated. The obtained crystal structures were found to be in good agreement with those from experiments. From the formation energy calculation of AKN solid solutions, the coexistences between Pbcm and Pmc21 phases and between Bmm2 and Pm phases were found to be in the composition ranges of x<"0.46" and x>"0.46," respectively. Therefore, the MPB separating the antiferroelectric and the ferroelectric phases can be specified at x ≈ "0.46." This theoretical study provides x ≈ "0.46" as a suggestive composition probably useful to acquire superior piezoelectricity for the utilization of AKN with reduced volatility of alkali elements at the A-site. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a materials design for tuning the CO2‐capture capability of mixed‐metal‐organic framework mmen‐(ZnxMg1‐x)2(dobpdc) using density functional theory. The structural stability of a mixed‐metal structure with respect to its parent single‐metal species was investigated via energy of mixing (ΔEmix). We found that the ΔEmix of all mixed‐metal structures are negative, signifying exothermic mixing. This then indicates that mixed‐metal structures are energetically preferable compared with their non‐interacting single‐metal species. Moreover, the magnitudes of ΔEmix of all mixed‐metal structures are lower than 1 kJ/mol, implying an ‘ideal mixing’. Density‐of‐state analysis also reveals that the electronic structures of both Mg and Zn in mixed‐metal structures are not significantly different from those in parent single‐metal species, suggesting weak chemical interaction between Mg and Zn in mixed‐metal structures. For CO2‐adsorbed mmen‐(ZnxMg1‐x)2(dobpdc), we found that the adsorption energy (Eads) is a linear function of mixing ratio (x), and does not depend on how Mg and Zn atoms are arranged in forming different mixed‐metal structures. This can be described by the weak chemical interaction between Mg and Zn in a mixed‐metal structure. Consequently, Eads can then be predicted conveniently from the mixing ratio, while the adsorption properties of parent single‐metal species can be tuned with the proposed mixed‐metal method. We then expect that the knowledge of materials design using a mixed‐metal approach presented in this work would benefit the community in providing the ability to tune CO2 capture capability efficiently in the materials studied. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The 0.93PZN-0.07BT ceramics containing 0.5 wt% AuNPs sintering was carried out for 3 – 5 h at various temperatures ranging from 1100 to 1150°C. The effect of AuNPs on 0.93PZN-0.07BT local structure and dielectric properties were investigated. The AuK-edge XANES spectrum indicated that AuNPs are not substituted into 0.93PZN-0.07BT structure. The dielectric constants and dielectric loss of 0.93PZN-0.07BT ceramics containing 0.5 wt% AuNPs after sintering at 1050°C for 3–5 h are higher and lower than that of 0.93PZN-0.07BT ceramics without AuNPs after sintering at 1100°C for 3–5 h, respectively, which can be described by assuming the connectivity series between the ceramics and the metal phases. In addition, Curie temperature shifting of 0.93PZN-0.07BT ceramics containing 0.5 wt% AuNPs due to the higher degree of chemical heterogeneity caused by the AuNPs addition. Therefore, the including of AuNPs into 0.93PZN-0.07BT ceramics can be improving dielectric properties with lower temperature and shorter time in sintering process. [ABSTRACT FROM PUBLISHER]

Lead zirconate titanate - lead zinc niobate (PZT-PZN) powders were prepared by a modified mixed-oxide synthetic route via a combination of Zn2Nb34O87 precursor and vibro-milling techniques. The effects of calcination temperature and chemical composition on phase formation were investigated by x-ray absorption spectroscopy. The ZnK-edge x-ray absorption near edge structure (XANES) was simulated with PZT-PZN in pyrochlore phase and perovskite phase. The comparison between simulated and measured XANES shows the increasing perovskite phase formation of PZT-PZN with increasing calcination temperature and the optimization of calcination temperature lead to 100% yield of PZT-PZN in perovskite phase. In addition, the ZnK-edge x-ray absorption near edge structure (XANES) was simulated with various compositions of PZT in PZT-PZN. The comparison between simulated and measured XANES shows the increasing perovskite phase formation of PZT-PZN with increasing composition of PZT. The results show the optimization of calcination conditions lead to formation of PZT-PZN in perovskite phase. [ABSTRACT FROM PUBLISHER]

In this work, two coupled Artificial Neural Networks (ANNs) were proposed to determine the first two higher-order resonant frequencies in radial vibrational modes and their associate effective electromechanical coupling coefficient (keff) of the ring-shaped piezoelectric transformer. In the first network, the inputs to the ANN were composed of ring width-to-thickness ratio (w/t), ring thickness (t) and the modes of the first two higher-order resonances (R1 andR2). Then, the output from the first network, i.e. the universal resonant frequency (the resonant frequency (fr) multiplied by ring thickness (t)) in logarithmic form (ln(frt)), was later supplied to the second network along withw/tand the order of the vibrational modes (R1 andR2) to predict ln(keff). The data for this coupled ANNs modeling was derived from Finite Element calculation analysis on the ring-shaped piezoelectric transformer. From the results, while it was unlikely to obtain reliable predicted results with just one ANN, the use of coupled ANNs provides the prediction of universal resonant frequencies and the coupling coefficient with high accuracies even using only a few basic parameters, which are the ring geometries and the resonant modes (R1 orR2). Specifically, from the best ANN architectures, the mean absolute errors (MAE) are 0.000952 and 0.001558 in predicting ln(frt) forR1 andR2, and are 0.002564 and 0.001047 in predicting ln(keff) forR1 andR2 respectively. Furthermore, theR-squared's of the scattering plots between predicted and targeted outputs are all higher than 0.98, which confirms the trustworthy of the model. Therefore, from this coupled ANNs design, it becomes possible to model complicated process with just only a few basic parameters. Explicitly, in this work, important parameters required for constructing highly efficient piezoelectric transformer were achieved without the needs to go through lengthy complex impedance spectrum analysis as necessitated in the conventional processes. [ABSTRACT FROM PUBLISHER]

In this work, we used density functional theory to study the structures, formation energy and order–disorder structural transition temperature (To) of L10FePt with Ag additive. The results show that an Ag atom substituting for a Fe site is more energetically preferable than that of substituting for a Pt, thus Ag atom should replace Fe site. We found thatTois significantly suppressed by Ag impurity because of the increasing in configurational entropy, whereas the magnetism tends to decrease due to the absence of some Fe atom in doping processes. The decrease inTocould open the opportunity to prepare FePt with lower temperature and small grain size for the high density magnetic recording media application. [ABSTRACT FROM PUBLISHER]

This study investigated the effect of morphologies between ordered and disordered structures on the internal quantum efficiency (IQE) of organic solar cell in two dimensions using kinetic Monte Carlo simulation. The results showed that the IQE has strong relationship with the morphological parameters such as interface area between P- and N-types, the amount of P- and N-type materials in the domains connected to the electrodes and percolation behavior of the materials across the electrodes. However, the relationship among IQE and the morphology parameters was found rather complicated and even non-linear fit to predict the outcome of IQE from the input parameters does not work well. Therefore, a knowledge based modeling, i.e. Artificial Neural Network (ANN), was used to predict the quantitative behavior of IQE. From the ANN results, the predicted IQE dependent on the morphological parameters agree very well with the targeted results. This therefore proves that the IQE database constructed using ANN is accurate and could be served as the foundation for higher dimension in the future. [ABSTRACT FROM PUBLISHER]

In this work, we used the density functional theory to predict the stability of CH3NH3SrI3by constructing a chemical potential diagram. We found that there are stability regions of CH3NH3SrI3for tetragonal and orthorhombic structures. TheGWapproximation including spin-orbit coupling (SOC) predicted that CH3NH3SrI3is a wide band gap semiconductor. In addition, the structural and optical properties as a function of strontium concentration (x) in CH3NH3Pb1-xSrxI3were also investigated and it displays the linear dependence on concentration. The results indicate the tunability and its potential as an alternative for using lower concentration of lead in organic-inorganic halide perovskite. [ABSTRACT FROM PUBLISHER]

Preisach-based method was used to characterize a series of BaTiO3hysteresis loops with varying external field frequencies. A stochastic adjustment of hysterons' weight was performed to obtain the Preisach densities. These densities, in representing the hysteresis responses, were characterized with three key parameters of the 3-dimensional hyperbolic-like distribution. One of the parameters relates directly to coercivity, while the other two concurrently represent polarization derivatives close to the coercivity, and emphasize an adaptability of the material to the external field around the main body of the loops. Thus, this approach can be extended to characterize other series of hysteresis loops to study changes of material responses influenced by varying external field frequency factor. [ABSTRACT FROM PUBLISHER]

In this work, Artificial Neural Network was used to model the hysteresis behavior of lead zirconate titanate-lead zinc niobate (Pb(Zr1/2Ti1/2)O3−Pb(Zn1/3Nb2/3)O3or (1-x)PZT-(x)PZN mixed ferroelectric systems. The hysteresis loops were measured with varying electric filed parameters and the composition x of the mixed ferroelectrics. A knowledge-based technique, i.e. the Artificial Neural Network (ANN), was employed in modeling the hysteresis to construct the database of how field parameters and the mixed composition affect dynamic hysteresis behavior. The input data to the ANN were composition x, field amplitude E0and field frequency f, where the output data was the hysteresis area. The inputs-outputs were divided into training, validating and testing datasets for the ANN. Multilayer perceptron with back propagation training algorithm was applied in this work. Exhaustive search was used to obtain the best network algorithm that gives minimum error in the training process. With the best network, unseen input datasets were fed into the network to predict hysteresis area. From the results, the predicted and the actual data match very well over an extensive range of field parameters, where the scattering plot between the predicted and the actual area has R-squared greater than 0.99. This therefore indicates ANN capabilities in modeling dynamic-hysteresis phenomena across (1-x)PZT-(x)PZN systems even they have different ratios of structural phases at microscopic level. [ABSTRACT FROM PUBLISHER]

In this work, Finite Element method (FEM) was used to model ring-shaped piezoelectric-transformers, using piezoelectric parameters from PZT-5H and having polarization along thickness direction. The resonator with full-covered electrode on top and bottom areas of the ring was firstly considered to investigate the dimensional effect on available vibrational modes. For modes above the fundamental, the results show that with increasing the ring thickness, the vibrational modes shift to lower frequencies. Similarly, with increasing the width, the resonant frequencies reduce. On the other hand, with increasing the ring-radius while keeping the width fixed, the resonant modes maintain. Eigenmode diagram of these resonant frequencies was also presented as databases for future use. Further, to enhance the power transferring efficiency, the electrode layouts were investigated where input and output electrodes were designed to correspond with electrical distribution of desired vibrational modes. The alternating and non-alternating electrode layouts were considered in this work. With the lumped-equivalent circuit model, the results show significant improvement of the considered resonant modes due to the enhancing of charge accumulation on the electrodes. In addition, the alternating electrode gives electromechanical coupling coefficient higher than that of the non-alternating electrode when operated at the same condition. This therefore implies the alternating electrode layout, corresponding to the electrical distribution of a particular vibrational mode, suggesting itself as a promising choice for implementation to achieve highly efficient piezoelectric-transformer. [ABSTRACT FROM PUBLISHER]

In this study, Monte Carlo simulations were used to investigate the ordered-disordered transition behavior of a two dimensional binary compound represented by Ising spins on square lattice. The spin exchange Kawasaki algorithm was use to update the system. With varying the system temperature and adhesive interaction strength, while keeping the cohesive interaction fixed, the system morphologies were investigated via the cluster (of the same spin) forming and the interface/surface area of the cluster. The results show that ferro-favorable systems exist only two large clusters (of the two binary species) at low temperatures. However, with increasing the temperature, the clusters reduce in size while their interface/surface area grows, becomes maximum and drop. This is due to the competitive effect between energy minimization by reducing the cluster size and the thermodynamic kinetic energy in diffusing Ising spins into random fashion. In addition, by increasing the adhesive interaction strength, even the ferro-type cluster forms, the cluster becomes smaller due to the introduction of anti-bonding between spins caused by stronger adhesive interaction. Diagrams of these phenomena which displays relationship among adhesive interaction, temperature, and the cluster of the same spin characteristic as well as the interface/surface area were given. These diagrams can be used as guides in enhancing the topic in acquiring desired applications having parts made from binary compound in which the interface characteristic is important. [ABSTRACT FROM AUTHOR]

This work studied the magnetic stability related to thermal distribution of heat pulse applying on FePt thin films using Monte Carlo simulation and Finite Element Method. The Ising model was used to represent magnetic characteristic of FePt in the calculation. The results show that the heat mostly diffuses downwards to the coupled heat sink, which causes the highest thermal gradient in this direction. Therefore, magnetization within this heating area decreases while the magnetization in the other area preserves its magnitude. [ABSTRACT FROM AUTHOR]

In this work, the thickness dependence of Fe3O4(111)/MgO thin films, were simulated using density-functional theory. From the results, even though the total DOS in bulk structure presents a half-metallic behavior, the DOS of all Fe3O4(111) films demonstrates that they are metallic. The specific magnetization as a function of film thickness is found to satisfy the inverse power law. Indeed, the noncompensation of spin moments is also observed to be the main majority effect in the enhancement of giant magnetization. Moreover, the high spin polarization value is discovered in the compensation models and tends to reach −80% with increasing the thickness. [ABSTRACT FROM AUTHOR]

In this work, the extend x-ray absorption fine structure (EXAFS) analysis was performed in combination with the density functional theory (DFT) calculation to investigate local structure of Mn-doped ((K0.5Na0.5)0.935Li0.065)NbO3. From the structural relaxation, Mn3+is substituted on Nb5+to produce oxygen vacancy in the longest bond length inc-axis. Further, from the EXAFS Fourier transform comparison inR-space, the bond lengths between Mn3+and O2−are almost equal in bothab- andc-axis with increasing Mn-doping contents. This is strong evidence that Mn-doping played an important role in producing the polarization domains in opposite direction, which diminish remnant polarization, pinning the domains wall movement and increase coercive field. [ABSTRACT FROM AUTHOR]

In this study, we used the kinetic Monte Carlo simulation to investigate the growth dynamic of the films on a substrate by imitating the chemical vapour deposition process. As a prototype, the system was confined into three–dimensional slap where the deposit chamber was divided into array grids. The vapour flowed in and out with varying rates and concentrations and the growth process took place on the substrate placed at the bottom of the array. Interaction among atoms was considered to take Ising–like, and Kawasaki algorithm is used in this study to observe the average thickness and its variance. The result shows that for the increasing temperature, the average thickness decreases at fixed rates and concentration. With increasing the rates, at fixed concentration, the average thickness decrease at low temperature. Furthermore, the average thickness greatly increases at low temperature with increasing the concentration, at fixed rates. [ABSTRACT FROM AUTHOR]

Ferromagnetic hysteresis behavior is a lagging relation between magnetization and external magnetic field. This understanding is useful for designing highly efficient magnetic applications e.g., magnetic recording devices. A magnetic phase and hysteresis properties fluctuate clearly when encountered with thermal noise. This creates difficulties in predicting and modeling; and poses a very challenging problem. In this study, we propose to fit parameters and select the suitable kernel functions of Support Vector Machine, of which the main tasks are i) managing the relationship among hysteresis properties, temperature, magnetic field, and magnetic frequency, and ii) classifying the symmetries of hysteresis. The results present a new novel of classifying symmetric behavior of hysteresis with high accuracy. [ABSTRACT FROM AUTHOR]

In this work, the Preisach technique was employed to characterize temperature dependent hysteresis loops extracted from the Ising model considered under the mean-field (MF) framework. In constructing the Preisach densities for these MF loops, a stochastic process was used to optimize the hysterons’ weight. Then, from the obtained Preisach densities, series of the MF hysteresis loops were accurately re-constructed, and the temperature independence of densities was observed. In addition, an increase of reversible polarization and a decline of irreversible polarization with increasing temperature were evident. These phenomena were examined and found to be caused by the enhancement of thermal fluctuation at higher temperature, which alleviates the spin flipping viscosity and lessens the phase-lag in hysteresis characteristic. [ABSTRACT FROM AUTHOR]

In this work, the critical temperature of Ising ferromagnetic and anti-ferromagnetic systems in 2 dimensions was extracted via finite-size-scaling analysis on the order parameter calculated from the discrete Fourier transformation. Spin patterns under the effect of thermal fluctuation were generated using Monte Carlo simulation. The discrete Fourier transformation was used to transform spin patterns from spatial domain to wave vector domain, where the order parameter was calculated from this Fourier-harmonics. From the result, it was found thatTC= 2.2684 ± 0.0006J/kBfor ferromagnetic system andTC= 2.2689 ± 0.0003J/kBfor anti-ferromagnetic system which match well with the exact theoretical valueTC≈ 2.269J/kB. As can be seen, the critical temperatures of both systems match well with the exact theoretical values. This study is therefore proposing a fundamental knowledge to extract critical behavior from complicated systems, where the exchange parameter is a periodic function of distance. [ABSTRACT FROM AUTHOR]

In this work, x-ray absorption spectroscopy was performed to characterize Mn-doped Bi3.25La0.75Ti3O12(BLT) ceramics with various MnO2dopants. The x-ray absorption near-edge structure (XANES) was analyzed in combination with first principle calculation of MnK-edge to identify atomic position of Mn in BLT. The result confirms Mn4+substituting on Ti4+-site in BLT. Further, the extended x-ray absorption fine structure (EXAFS) was examined where MnK-edge of Mn-doped BLT was compared to that of TiK-edge of BLT inR-space. The result shows radial distances between Mn4+and O2−ions inab-axis are almost equal and decrease with increasing Mn-doping contents. This is strong evidence that Mn4+substituting on Ti4+site can be reduced the orthorhombicity, which increase the polarization domains size and enhance remnant polarization, speed up the polarization domains movement and lessen coercive field. [ABSTRACT FROM AUTHOR]

In this work, we have investigated the ferroelectric property of BiAlxGa(1−x)O3withx =0.00, 0.25, 0.50, 0.75, and 1.00 for replacement of the widely use, PZT which is toxic. The techniques used are density functional theory with local density approximation (LDA) as well as projector augmented-wave method (PAW). The composition (x) was varied via setting the appropriated supercell. The solid solutions in both tetragonal (P4 mm) and rhombohedral (R3c) phase have been simulated to determine crystal stability, phase transition, and ferroelectric properties. From the results, the expected morphotropic phase boundaries (MPB) have not been observed because allR3cstructures are more energetically stable than those ofP4 mm. Therefore, Bi(Ga,Al)O3solid solution cannot display higher ferroelectricity than that of pure BiGaO3. However, the calculated polarization of Bi(Ga,Al)O3are still very high compared to other ferroelectric materials, e.g. AgNbO3and BaTiO3. This suggests that the considered solid solution could be one of lead-free candidates for future industrial applications. [ABSTRACT FROM AUTHOR]

In this work, we developed a finite element package to investigate the dependence of electromechanical coupling coefficient on ring-shaped piezoelectric transformer parameters, and proposed how to design the transformer in achieving optimum efficiency using the ceramic PZT-5H as an application. The ring transformer firstly used full driven electrode to observe piezoelectric vibration characteristic with varying the ring dimensional (structural) parameters. Then, with the optimized ring parameters, electrode layout was designed in accordance to the distribution of electrical potential within the ring transformer, where both alternating and non-alternating electrode layouts were considered. From the calculation, results showed that the piezoelectric vibration characteristic strongly depends on the ring-shaped transformer dimension. Specifically, with increasing piezoelectric ceramic thickness and the width between inner- and outer-ring-radius, the resonance frequencies of the transformer decrease. On the other hand, in terms of the electrode layouts, the alternating electrode was a better choice in obtaining desired resonance frequency mode, as it provides larger electromechanical coupling coefficient than the non-alternating electrode. These results are in agreement with previous experimental investigation, where applicable. [ABSTRACT FROM PUBLISHER]

Thermal expansion properties have been measured for the ceramic lead zirconate titanate-lead zinc niobate [(1 − x)PZT-( x)PZN] in the temperature range of −100 to +450 °C. For all ceramics examined, the deviations from the straight line below Burns temperature were observed. The dynamic polarization fluctuations in their relaxor compositions are believed to play a role in this deviation. Burns temperature was determined and the local polarization ( P) was calculated from the thermal expansion data. Various aspects of understanding the polarization behavior and other effects in this ferroelectric system were examined and discussed. [ABSTRACT FROM AUTHOR]

In this work, Monte Carlo simulation was used to study the size dependence of the dynamic hysteresis properties of 2 dimensional ferroelectric system. The DIFFOUR model and Metropolis algorithm were used to investigate the size effect on hysteresis properties. From the simulation, it was found that the competition between the electric field parameters and the system size plays a crucial role on the phase-lag between the polarization and the electric field signals, which defines particular hysteresis properties. In describing the hysteresis behavior qualitatively, finite size scaling formalism, in a power law form, was used to predict relations among the field parameters, system size, and hysteresis. The purpose was to establish phenomenological knowledge of how dynamic perturbations affect the hysteresis in finite ferroelectric system. Comparison with related experiments was also discussed. [ABSTRACT FROM PUBLISHER]

In this work, Monte Carlo simulation was used to investigate the ferroelectric films behavior using the DIFFOUR Hamiltonian. The considered electric dipole directions were considered to range from 2 to 14 directions, in representing various domain structures. Metropolis algorithm was used to extract the polarization, the susceptibility, and critical behavior for each domain structure. It was found that the critical temperature increases with increasing the films thickness due to stronger ferroelectric interaction, but reduces in structure with more possible dipole-switching directions due to lower energy barrier. Scaling of the critical temperature with films thickness and its shifting exponent are reported. [ABSTRACT FROM PUBLISHER]

This paper proposed an application of Artificial Neural Network (ANN) to concurrently model ferroelectric hysteresis properties of Barium Titanate in both single-crystal and bulk-ceramics forms. In the ANN modeling, there are 3 inputs, which are type of materials (single or bulk), field amplitude and frequency, and 1 output, which is hysteresis area. Appropriate number of hidden layer and hidden node were achieved through a search of up to 2 layers and 30 neurons in each layer. After ANN had been properly trained, a network with highest accuracy was selected. Query file of unseen input data was then input to the selected network to obtain the predicted hysteresis area. From the results, the target and predicted data were found to match very well. This therefore suggests that ANN can be successfully used to concurrently model ferroelectric hysteresis property even though the considered ferroelectrics are with different domains, grains and microscopic crystal structures. [ABSTRACT FROM AUTHOR]

This work performed Monte Carlo simulation of ferromagnetic Ising spins in 2 dimensions to investigate the hysteresis properties, of both symmetric and asymmetric types, under the effects of external perturbations using the Fourier analysis. The hysteresis loops were analyzed using the discrete Fourier transformation. From the results, the hysteresis areas of both symmetric and asymmetric hysteresis depend on the amplitude of magnetic field and the Fourier coefficient of the first harmonic of real part. Nevertheless, the remnant magnetization of symmetric hysteresis depends only on the Fourier coefficients of odd harmonics of real part, while that of asymmetric hysteresis depends on both the Fourier coefficients of the zero and odd harmonics of real part. Additionally, the coercive field of symmetric hysteresis depends on the amplitude of magnetic field and the Fourier coefficients of the first harmonics of both real and imaginary parts. This suggests that the hysteresis behavior can be classified and modeled in frequency domain using the Fourier analysis. [ABSTRACT FROM AUTHOR]

In this work, the effect of random vacancy defects on the electrical properties of ferroelectric thin-films was studied. The Monte Carlo simulation, based on the ferroelectric DIFFOUR model, was performed in the lattice system with free and periodic boundary conditions. The Metropolis algorithm was considered in choosing the proper states under the presence of the electric field. From the results, the hysteresis area at a given field was found to depend on the thickness of thin films and the vacancy defects of system. For instance, in thicker films, the larger hysteresis area was observed, which is resulted from the stronger ferroelectric interaction. On the other hand, the hysteresis area decreases with increasing vacancy concentration, due to the reduction of ferroelectric interaction on the average. To understand the hysteresis behaviors, the scaling exponents of associated parameters in the power law scaling form were considered. The results were discussed and compared with these from literatures. [ABSTRACT FROM AUTHOR]

In this study, the Monte Carlo Simulation was used to investigate the powder structure of magnesium oxide (MgO) undergoing the mechanical milling process as functions of milling time, initial temperature, milling frequency and amplitude of milling, in contacting with a heat bath. The Kawasaki algorithm was used to simulate the 'Ising powder' in a two-dimensional space. By allowing the shearing and diffusion effects, the competition between these two determines the sizes of the powders. The results show that the shearing effect reduces the particle sizes as the time goes while the diffusion effect enlarges the particle sizes. Furthermore, at fixed milling frequency and maximum amplitude of milling, both milling from adiabatic and heat exchange processes show that the maximum powder sizes are about the same at the beginning. However, at long milling time, the adiabatic and heat exchange processes provide smaller powder size as the system temperature is much larger that of the heat bath. Furthermore, the maximum size of powder takes longer time to form at the lower temperature, larger amplitude of milling, and longer milling time. As a result, this work suggests of how mechanical action and thermal effect play a crucial role on power size reduction at microscopic level. [ABSTRACT FROM AUTHOR]

In this work, Monte Carlo simulation was used to investigate the Debye dielectric behavior of mixed normal- and relaxor-ferroelectrics. The results show that, with increasing temperature, the dielectric permittivity of the mixed system sharply increases at low temperatures but slowly decays at high temperatures, while still presenting the dielectric peaks close to the relaxor- and normal-ferroelectrics transition temperatures. Further, it is found that the sharpness, the magnitude, and the frequency dispersion of the dielectric peaks can be finely tuned by adjusting relevant normal-ferroelectric parameters in the model. However, the modified Curie-Weiss law shows that its exponent γ is governed by the inverse-temperature dependence as the exponent is very close to 2 regardless of normal-ferroelectric content. The functionalities of the Debye-type dielectric permittivity are then discussed along with the comparison with experiments. [ABSTRACT FROM AUTHOR]

Effects of compressive stress on the dielectric and ferroelectric properties of commercial soft PZT ceramics were investigated. The dielectric and ferroelectric properties were measured under compressive stress applied parallel and perpendicular to an electric field direction. The results showed that the dielectric properties; i.e. the dielectric constant (εr) and dielectric loss tangent (tan δ), and the ferroelectric characteristics; i.e. the area of ferroelectric hysteresis (P-E) loops, the maximum polarization (Pmax), the coercive field (Ec) and the remanent polarization (Pr), changed significantly with increasing compressive stress. These changes depended greatly on direction of the applied stress. The stress clamping of domain wall, de-ageing and non-180° ferroelectric domain switching processes are responsible for the changes observed. In addition, a significant decrease in those parameters after a full cycle of stress application has been observed and attributed to the de-poling and stress-induced decrease in switchable part of spontaneous polarization at high stress. This study clearly showed that the applied stress has significant influence on the electrical properties of soft PZT ceramics. [ABSTRACT FROM AUTHOR]

The dielectric and ferroelectric properties of (1-x)Pb(Zr1/2Ti1/2)O3-(x)Pb(Ni1/3Nb2/3)O3 or (1-x)PZT-(x)PNN (x = 0.1-0.5) ceramics were measured under compressive stress applied perpendicular to an electric field direction. For the dielectric properties, the experimental results revealed that the superimposed perpendicular compression stress reduced the dielectric constant and the dielectric loss tangent of all compositions. The stress-induced changes the dissipation energy, the polarizations, however, depended significantly on ceramic compositions, but increases the coercive field of all the compositions. These results were interpreted through the non-180° ferroelastic domain switching processes, the stress clamping of domain walls, de-aging mechanism, and the stress induced enhance in switchable part of spontaneous polarization. [ABSTRACT FROM AUTHOR]

In this work, Monte Carlo simulation was used to study the grain size dependence of ferromagnetic properties. The Ising model and the spin flip algorithm were used to observe the grain size effect on both static and dynamic properties. From the results, it was found that the competition between the grain size and cluster size of same spins (which is controlled by the dipolar interaction) plays a crucial role on ferromagnetic behavior. For instance, at a particular grain size, the ferromagnetic phase transition shifts to a lower temperature with increasing the dipolar magnitude. On the other hand, by increasing the grain size, the ferromagnetic hysteresis can either be enhanced or deteriorated depending on the magnitude of the dipolar interaction, where to some extent agree with applicable experiments. This therefore suggests a way to tune the ferromagnetic properties by varying the grain size or the dipolar magnitude. [ABSTRACT FROM AUTHOR]

In this study, the artificial neural network (ANN) was used to model ferromagnetic Ising hysteresis obtained from mean-field analysis as a case study. ANNs were trained to predict the effect of external perturbations, which are the temperature, the field amplitude and the field frequency, on the hysteresis properties, which are the hysteresis area, the remanence magnetization and the coercivity. The input data to the ANN were split into training data, testing data and validating data. Search were carried out to identify number of hidden layer and number of hidden nodes to find the best architecture with highest accuracy. After the networks had been trained, they were used to predict hysteresis properties of the unseen testing patterns of input. The predicted and the actual data were found to match very well over an extensive range. This therefore suggests a success in modeling ferromagnetic hysteresis properties using the ANN technique. [ABSTRACT FROM AUTHOR]

Effects of compressive stress applied perpendicular to electric field on dielectric properties of (1-x)Pb(Zr1/2Ti1/2)O3-(x)Pb(Zn1/3Nb2/3)O3 (x = 0.1-0.5) ceramics were investigated. The results showed that the superimposed compression stress had pronounced effects on the dielectric properties of PZT-PZN ceramics. With increasing compressive stress the dielectric constant of the ceramics decreased, while the dielectric loss tangent increased. The observations were mainly interpreted in terms of competing influences of the domain switching through non-180° domain walls, clamping of domain walls, and de-aging mechanisms. Interestingly, the observed changes of the dielectric properties with the perpendicular compressive stress were generally similar to those under the parallel stress. [ABSTRACT FROM AUTHOR]

The influences of compressive stress on the dielectric properties of (1-x)Pb(Zr1/2Ti1/2)O3-(x)Pb(Co1/3Nb2/3)O3 (x = 0.1-0.5) ceramics were investigated in this study. The dielectric properties were measured under compressive stress applied parallel and perpendicular to an electric field direction. The results clearly showed that the superimposed compression stress had pronounced effects on the dielectric properties of PZT-PCN ceramics. In general, with increasing compressive stress (applied parallel with the electric field direction) the dielectric constant of the ceramics increased, while the dielectric loss tangent decreased. Interestingly, the observed changes of the dielectric properties with the perpendicular compressive stress were opposite to those under the parallel stress. [ABSTRACT FROM AUTHOR]

In this work, Monte Carlo simulation was used to model the ferroelectric behavior of mixed normal and relaxor ferroelectrics using the single polarization-flip algorithm. The purpose is to investigate the dependence of ferroelectric properties on the field frequency, the temperature and the normal ferroelectric concentration in the relaxor ferroelectrics. Results obtained from both static and dynamic simulation stress the significant effect of the larger ferroelectric interaction caused by the normal ferroelectric contents. For instance, with increasing normal ferroelectric concentrations, the transition between zero and nonzero polarization phases shifts to a higher temperature due to stronger ferroelectric interaction. In addition, the stronger ferroelectric interaction also causes less polarization switching, where the hysteresis gets larger in size at low frequencies, but smaller at high frequencies. This strong ferroelectric interaction also shifts the frequency at maximum phase-lag between polarization and field signal to a lower frequency. These results are in good agreement with experiments, where applicable. [ABSTRACT FROM AUTHOR]

In this study, the Monte Carlo simulation was used to investigate relaxor films using the spin-glass Hamiltonian with the surface effect. The single polarization flip algorithm was used to update the local polarizations where the relaxation time was measured to calculate the dielectric permittivity and loss as varying temperature, field frequency and films thickness. From the results, in the vicinity of the electrodes on the topmost and bottommost layers, the relaxor films exhibit thickness-dependent dielectric properties in qualitatively good agreement with experiments. The maximum dielectric permittivity enhances in the films with increasing the films thickness as expected. The relations of how maximum dielectric permittivity and its corresponding temperatures vary with thickness are also explained. [ABSTRACT FROM AUTHOR]

The Pb(Zr0.52Ti0.48)O3 ceramics with 0.75, 1.0, 1.25 and 1.50%wt of Nb2O5 addition were prepared by a conventional mixed oxide technique. It was found that the average grain size of the ceramics decreased from 6 to 1 μm with increasing doping concentration to 1.5%wt. The room temperature dielectric constant and d33 reached maximum values of 1050 and 285 pC/N, respectively, at 1%wt Nb-doping. The electrical coercivity (Ec) of Nb-doped PZT decreased, while the polarization values increased, with increasing doping concentration. Most importantly, this study shows that Nb2O5-doped PZT ceramics exhibits soft piezoelectric and enhanced ferroelectric behaviors, and the optimum properties can be obtained using suitable doping concentration. [ABSTRACT FROM AUTHOR]