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The dipole of a three-dimensional ferroelectric is distributed homogeneously in specific polarization directions related to its lattic orientations. Upon applied electric field, dipoles in all directions respond differently to electric field, resulting in various field-induced effects.The most basic effect is polarization induction effect by electric field sharply in the phase transition temperature region, which results in higher energy storage density in the corresponding temperature region. Based on the relationship between the three-dimensional Gibbs free energy and polarization in ferroelectrics from the Devonshire theory, the influences of the induced effect and reorietation of the dipole of ferroelectric on the polarization energy storage density and discharge energy density are obtained. The results show that the peak temperature of energy storage density under low electric field is lower than the Curie’s temperature, and it approaches and exceeds the Curie’s temperature with the increase of electric field. The ratio of two ferroelectric parameters has significant influence on the polarization behavior, hysteresis loop and energy storage density of ferroelectrics and causes their correlations, in which the temperature width of the dielectric peak corresponds to the temperature width of the shape change of hysteresis loop and the temperature width of the energy storage density peak. The higher the energy storage density peak is, the narrower the temperature area of the peak is.

Crystalline calcium aluminates are a critical setting agent in cement. To date, few have explored the microscopic and dynamic mechanism of the transitions from molten aluminate liquids, through the supercooled state to glassy and crystalline phases, during cement clinker production. Herein, the first in situ measurements of viscosity and density are reported across all the principal molten phases, relevant to their eventual crystalline structures. Bulk atomistic computer simulations confirm that thermophysical properties scale with the evolution of network substructures interpenetrating melts on the nanoscale. It is demonstrated that the glass transition temperature (T g) follows the eutectic profile of the liquidus temperature (T m), coinciding with the melting zone in cement production. The viscosity has been uniquely charted over 14 decades for each calcium‐aluminate phase, projecting and justifying the different temperature zones used in cement manufacture. The fragile–strong phase transitions are revealed across all supercooled phases coinciding with heterogeneous nucleation close to 1.2T g, where sintering and quenching occur in industrial‐scale cement processing., The evolution mechanism of different calcium‐aluminate phases during fast heating to about 3200 K and subsequent cooling is revealed by measuring their associated thermophysical properties (e.g., viscosity and density) using the self‐developed aerodynamic levitation technique and by bulk‐scale computationally modeling these properties and the atomistic structural changes. The fragile‐to‐strong phase transitions are discovered across all supercooled calcium‐aluminate liquids.

The bismuth layer-structured Na0.5Bi4.5-xPrxTi4O15 (x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5) (NBT-xPr3+) ceramics were fabricated using the traditional solid reaction process. The effect of different Pr3+ contents on dielectric, ferroelectric and piezoelectric properties of Na0.5Bi4.5Ti4O15 ceramics were investigated. The grain size of Pr3+-doping ceramics was found to be smaller than that of pure one, the maximum dielectric constant and Curie temperature Tc gradually decreased with increasing Pr3+ contents, and the dielectric loss decreased at high temperature by Pr3+-doping. Moreover, the activation energy (Ea), resistivity (Z’), remanent polarization (2Pr) and piezoelectric constant (d33) increased by Pr3+-doping. The NBT-xPr3+ ceramics with x = 0.3 achieved the optimal properties with the maximum dielectric constant of 1109.18, minimum loss of 0.00822 (250 kHz), Ea of 1.122 eV, Z’ of 7.9 kΩ cm (725 oC), d33 of 18 pC/N, 2Pr of 12.04 μC/cm2. The enhancement was due to the addition of Pr3+ which suppressed the decreasing of resistivity at high temperature and made it possible for NBT-xPr3+ ceramics to be poled in perpendicular direction, implying that it is a great improvement for Na0.5Bi4.5Ti4O15 ceramics in electrical properties.

New lead-free dielectric ceramics, Na 1+x BiTi 6 O 14+0.5x (x = −0.02, − 0.01, 0.01, 0.02), were prepared by the conventional solid-state method. Micro-structural and electrical properties of Na 1+x BiTi 6 O 14+0.5x were studied. XRD showed all the samples exhibited a single structured phase. Grains decreased at the beginning, then grew with the increasing x content in SEM. Impedance spectra (IS) analysis evidenced the phenomena that the dielectric permittivity increased firstly, then decreased, while the loss had the opposite trend. Z* plots showed that Na 1+x BiTi 6 O 14+0.5x ceramics were a kind of dielectrics. The activation energy ( E a ) could be calculated in the range of 1.53–1.65 eV, which indicated they were dielectric ceramics. Na 1+x BiTi 6 O 14+0.5x ceramics (x = 0.01) sintered at 1040 °C showed prominent dielectric properties with a dielectric constant of 25.76, loss of 0.07%, E a of 1.65 eV, density of 3.463 g/cm 3 , impedance of 0.532 MΩ cm, -Z′′ max of 0.1958 MΩ cm, capacitance of 5.56 pF/cm (600 ℃), which were enhanced much compared with other samples. The existence of dielectric properties with high dielectric constant, low dielectric loss and wide operating temperature range makes it possible to develop the ceramics into high-temperature capacitors.

As a new member of lead-free Na 0.5 Bi 0.5 TiO 3 (NBT) ceramics based on bismuth layer-structured ferroelectrics (BLSFs), Bi x Ti 3 O 6+1.5 x ( x = 3.96, 3.98, 4.0, 4.02, 4.04) ceramics was prepared by a conventional mixed oxide route. In order to explore the ferroelectric and dielectric properties, we changed the content of Bi in the ceramics. XRD patterns of Bi x Ti 3 O 6+1.5 x demonstrated that the new material was a single phase of Bi-layered perovskite structure. Through impedance spectra analysis, we found that the Bi 4.02 Ti 3 O 12.03 ceramics sintered at 1100 °C showed excellent dielectric properties with a highest dielectric constant of 8967.49 and a lowest dielectric loss of 0.00298 measured under 10 kHz, which were enhanced much compared with Bi 4 Ti 3 O 12 prepared by the same means. Meantime, the Curie temperature of the whole samples was about 670 °C. In addition, the ferroelectric hysteresis loops of all the samples indicated that they were ferroelectric materials, and Bi 4 Ti 3 O 12 ceramics sintered at 1100 °C processed a remanent polarization (2 P r ) of 12.206 µC/cm 2 and a coercive field of 29.542 kV/cm. SEM can roughly describe the results of the dielectric spectrum and ferroelectricity with different Bi concentration through grain size mechanics. Because of the high dielectric constant, wide operating temperature and low dielectric loss, the Bi 4 Ti 3 O 12 ceramics have a broad application prospect in components, such as sensors, high-temperature capacitors and so on.

As a new kind family of lead-free Na0.5Bi0.5TiO3 (NBT) ceramics, bismuth layer-structured ferroelectrics (BLSFs), Na0.5BixTi3.98Mg0.02Oy (x = 4.48, 4.50, 4.52) were synthesized by a conventional mixed oxide route. Studies have found that the dielectric properties of Na0.5Bi4.5Ti4O15 can be optimized through changing the Bi content of the ceramics or Mg-doping on Ti-site under different sintering temperatures. X-ray diffraction analysis indicated that the new material was in a single BLSFs phase. The dielectric constant of Mg-doped Na0.5Bi4.5Ti3.98Mg0.02Oy was improved and dielectric loss of Na0.5Bi4.5Ti3.98Mg0.02Oy changed slowly under 500 °C with the increased sintering temperature. We found that the dielectric properties of the sample sintered at 1120 °C with the highest permittivity of 1122.5 and the lowest dielectric loss of 0.01 were relatively better than those of the other samples. SEM can be better to explain the results of the dielectric spectrum at different sintering temperatures through grain size mechanics. Z* plots showed that Na0.5Bi4.5Ti3.98Mg0.02Oy ceramics are a kind of dielectrics. Thus, Na0.5BixTi3.98Mg0.02Oy (x = 4.48, 4.50, 4.52) can be used as high-temperature capacitors and phase shifter with high dielectric constant, low dielectric loss and wide operating temperature range.

Chiral ligand conjugated transition metal oxide nanoparticles (NPs) are a promising platform for chiral recognition, biochemical sensing, and chiroptics. Herein, we present chirality-based strategy for effective sensing of mercury ions via ligand-induced chirality derived from metal-to-ligand charge transfer (MLCT) effects. The ligand competition effect between molybdenum and heavy metal ions such as mercury is designated to be essential for MLCT chirality. With this know-how, mercury ions, which have a larger stability constant ( K f ) than molybdenum, can be selectively identified and quantified with a limit of detection (LOD) of 0.08 and 0.12 nmol/L for D-cysteine and L-cysteine (Cys) capped MoO 2 NPs. Such chiral chemical sensing nanosystems would be an ideal prototype for biochemical sensing with a significant impact on the field of biosensing, biological systems, and water research-based nanotoxicology.

Using the vanadium oxyacetylacetone (VO(AcAc)2) as the precursor and white powdery tungstic acid as the doping W source, we fabricated the W-doped porous VO2 films by spin-coating method followed by annealing under the N2 atmosphere at 550 °C for half an hour. Compared to the pure VO2 film, the 5 at.% W-doped film exhibits a simultaneous enhancement of the near-IR switching efficiency at 2000 nm from 47.5 to 55.0 % and the maximum value of visible transmittance at 30 °C from 39.5 to 46.7 % as well as the one at 90 °C from 44.7 to 58.1 %, which further confirmed the practicability of introducing pores into the VO2 film as a strategy to enhance the thermochromic properties. In addition, a possible connection is presented about the relationship of metal–insulator transition process and the evolution of the phase compositions and morphology. A possible connection between the morphology and the thermochromic performance for the W-doped VO2 films was presented.

The increasing interest and rapid progress in the artificial neural networks have driven extensive research in resistive switching memory based on various insulators and two-dimensional nanomaterials. Herein, we have demonstrated a kind of resistive switching memory device based on GaSe layered nanorods fabricated by liquid phase exfoliation (LPE) method with a lateral graphene/GaSe/graphene structure. The single crystalline GaSe layered nanorods mixed with a few nanoflakes were synthesized by shear and ultrasonic (bath and probe) exfoliation methods, which showed high quality and hexagonal crystalline structure. The electrical properties and the resistive switching behavior were investigated, indicating the charge trapping/detrapping effect is the dominant resistive switching mechanism. This work suggests a novel strategy to develop the resistive switching devices based on various 2D materials by using LPE method, and these 2D-nanomaterials-based memristors have the potential to be used for constructing neuromorphic computing systems.

The energy release effect is an effect that happens during the process of withdrawing the electric field after charging electric energy into the materials, which can be represented by the amount of recoverable energy storage density. On the basis of the previously derived relationship between the antiferroelectric hysteresis loop with temperature from the phenomenological theory by considering two different responses of the two polarizations in opposite directions to an applied electric field, the relationship between the recoverable energy storage density with temperature during the process of withdrawing the electric field is systemically studied in the second-order phase transition antiferroelectrics. The results show that there are two peaks of the recoverable energy storage density in the temperature spectrum: the smaller energy density peak is in the antiferroelectric phase, and the other larger peak is in the paraelectric phase at the temperature slightly higher than the Curie temperature. When the temperature decreases from the Curie temperature, the recoverable energy storage density will gradually increase to the smaller peak and then slowly decrease. This conclusion is consistent with many experimental results on antiferroelectric materials including ceramics, thin films, and single crystals. The further analysis of the effect of the Gibbs free energy on the energy release effect shows that the two coefficients of the Gibbs free energy are essential for the width and height of the peak of recoverable energy storage density. Specifically, the smaller is the coefficient of the quadratic power of polarization, the wider is the temperature width of the peak, or temperature stability, the smaller is the coefficient of the fourth power of polarization, and the higher is the height of the released energy peak. These two parameters dominate the behaviors of polarization, energy storage characteristic, and the dielectric constant of the antiferroelectrics, and establish the correlation between the dielectric constant peak and the higher energy storage density peak. Therefore, the basic energy release effect can be determined from the dielectric properties.

In the three dimensional Landau-Devonshire ferroelectric theory, polarization is a variable of the Gibbs free energy function. The first derivative of the Gibbs free energy to polarization can be used to derive equilibrium values of the polarization and the energy level. When an external electric field ( E ) is applied, the derived polarization and energy level change according to angular degree between the polarization and the E , which can be derived by solving the Gibbs free energy function associated with the electric field. In the E direction the polarization increases with decreased Gibbs free energy level, in the anti- E direction the polarization decreases with increased Gibbs free energy level, and in the directions perpendicular to the E direction, polarization and the Gibbs free energy remain unchanged. If change in a Gibbs free energy level happens, the proportion of the dipole that forms the polarization will also change accordingly, which is derived by solving the Boltzmann distribution function via taking the Gibbs free energy as equilibrium energy level. The result demonstrates that proportion of the dipoles in the E direction increases, and proportions of the dipoles in other directions decrease. The changes in proportions of the dipoles between different directions can be described as turning of dipoles. This turning of dipoles to the E direction causes decrease in the entropy of dipole alignment, and the change in the entropy produces exothermal effect in adiabatic condition. On another aspect, a coupling effect will happen on the parallel aligned neighbor dipoles in the E direction by the action of the electric field to form reversible ferroelectric domains. When the E withdraws, the domains decouple. The coupling or decoupling of the reversible domains corresponds to exothermal effect or endothermal effect, respectively. As the coupling effect of dipoles causes electric hysteresis loop, the coupled thermal effects can be deduced from the polarization of the hysteresis loop which is associated with temperature and the electric field. The result shows that the change in entropy results in an exothermal peak, which shifts to higher temperature with the increase of E , even across the Curie temperature, under higher electric field. The coupling effect of the parallel aligned dipoles produces exothermal effect, decreasing with increase of temperature continuously. The present theoretic results can explain the relevant experimental results by numerical simulation of the derived equations.

Porous thermochromic pure and tungsten (W)-doped vanadium dioxide (VO2) films have been prepared on silica substrates by spin coating via a sol–gel process and annealing in ammonia (NH3) atmosphere. NH3 with weak reducing capacity can prevent V4+ from further oxidization and contribute to the formation of porous structure. These films exhibit enhanced visible transparency and switching property at near-infrared wavelengths across the metal–insulator transition (MIT). The transmittance change in the VO2 film annealed at 2.0 × 103Pa is as high as 52.9 % at λ = 2000 nm, and its solar modulation efficiency reaches up to 9.4 %. W-doping shifts the MIT temperature of the VO2 films from 55 to 28 °C, while the films remain the excellent modulating ability in near-infrared region, and the decreasing efficiency of V0.99W0.01O2 film can achieve to 20 K/at.%, which will greatly favor the practical application of VO2-based smart windows. Transmittance spectra for pure VO2 film in the range of 250–2500 nm and the recorded transmittance–temperature hysteresis loop in the range of 20–90 °C of the W-doping VO2 films after annealing at 500 °C for 30 min (middle inset).

Rutile TiO 2 nanorod arrays were grown on TiO 2 seed layer coated fluorine doped tin oxide (FTO) substrate by a hydrothermal method. The effects of the thin TiO 2 seed layer on the morphology of nanorod arrays, as well as the photovoltaic performance in dye-sensitized solar cells (DSSCs) were analyzed. The introduction of the TiO 2 seed layer was found to significantly increase the density and vertical orientation of the nanorod arrays, which lead to the improvement of dye absorption and electron transport. By optimized the TiCl 4 solution concentration, a power conversion efficiency of 2.55% can be achieved in a DSSC fabricated by TiO 2 nanorod arrays grown on seeded-FTO substrate using 0.15 M TiCl 4 solution, which is 126% higher than the DSSC fabricated by nanorod arrays grown on bare FTO substrate (1.13%).

Samples of As18SxSe82-x glasses were prepared by conventional melt-quenching techniques with As, S and Se of 99.99% purity. Raman spectra of samples were obtained by a Fourier transform Raman spectrometer. In addition, all calculations based on Hartree-Fork theory have been used to investigate the Raman-active modes of AsSnSe3-n clusters. It can be found that the calculated data of basic cluster models are in excellent agreement with observed Raman spectra. We give an explanation about the Raman shift of main vibrational modes in AsSnSe3-n clusters.

Ba0.7Sr0.3TiO3 (BST) thin films were deposited on Pt and SrRuO3(SRO)/Pt hybrid bottom electrodes by radio frequency magnetron sputtering. X-ray analysis indicated that both films were polycrystalline. Dielectric measurements showed that the films on SRO/Pt hybrid bottom electrode had lower dielectric constant and loss than the films on single Pt and the dielectric properties were frequency-independent. The leakage current density of Ba0.7Sr0.3TiO3 thin films on hybrid bottom electrode was also lower. Leakage mechanism investigations showed that the contact between the electrode-film interfaces of thin films on SRO/Pt hybrid bottom electrode was ohmic. Based on the results, the effects of SRO/Pt hybrid bottom electrode on the crystallization and electrical properties of BST thin films were discussed.

Amorphous thin films of GeSe2 and GeSe4 were prepared by the pulsed laser deposition (PLD) technique. Refractive index, thickness and optical band gap (E opt g ) of the films were abtained from the optical transmission spectra and absorption spectra, respectively. Based on the ‘non-direct transition’ model proposed by Tauc, the absorption edges can be well fitted. As an indicator of the degree of structural randomness of amorphous semiconductors, the Tauc slopes of the prepared thin films were discussed. The dispersion of refractive index was analyzed in terms of the single-oscillator Wemple-Di Domenico model. For asdeposited films, after annealing below the glass transition temperature (Tg), the drop of refractive index and the increase of E opt g can be clearly observed. The thermal-bleaching effect was proposed to the reduction in the density of homopolar bonds confirmed by the Raman spectra analysis. The thermal-contraction effect was ascribed to the elinimination of porous structure of the as-deposited films. © 2009 Elsevier B.V. All rights reserved.

Barium strontium titanate (Ba1−x Sr x )TiO3 (BST) thin films were deposited on Pt, Ru, RuO2, and Pt/RuO2 electrodes by radio frequency magnetron sputtering. The interfacial structure characteristic of the BST films deposited on various electrodes was investigated. X-ray photoelectron spectroscopy investigations showed that the interfacial diffusion layer in BST/Pt and BST/Ru are approximately 6 and 10 nm, respectively. The BST films are short of Ba and O elements comparing with the stoichiometry Ba0.65Sr0.35TiO3 in the interface region. Dielectric measurement of the BST films with thickness ranging from 70 to 400 nm revealed that the BST films deposited on Pt and Pt/RuO2 bottom electrodes have similar dielectric property, the BST films deposited on Ru have the highest bulk dielectric constant, and the thickness dependence of dielectric constant on the BST film deposited on RuO2 electrode can be neglected. The interfacial layer dielectric constant of BST films deposited on Pt and Ru electrodes are estimated to be about 34.5 and 157.1, respectively. The effect of interfacial dead-layer on the dielectric constant could be eliminated through selecting appropriate bottom electrodes.

The influence of lattice strain on the strength of dipoles in the Ho3+-doped barium-strontium titanate (BST) thin films has been analyzed. Thin films were produced by using the sol–gel technique on Si substrate. The resulting stress due to fabrication process was quantified by analyzing the {200} planes of the cubic perovskite structure and comparing them with the data for bulk materials. The influence of strain and changes due to Ho3+-ion doping were characterized by Raman and visible photoluminescence spectroscopy, which clearly show the evidence for the increased tetragonality due to weaker dipole interaction at B-sites of cubic perovskite in the presence of Ho3+-ions at concentrations larger than 3 mol%. The film strain can therefore be controlled to enhance the intensity of emitted light at 650 nm.

La0.67Sr0.33MnO3 (LSMO) films were prepared on SrTiO3 single-crystal substrates by the pulsed laser deposition method. X-ray photoelectron spectra (XPS) were measured for the LSMO films as-prepared, annealed in oxygen and in vacuum, respectively. Multiple peaks fitting for Mn 2p3/2 XPS spectra shows that Mn2+ appears and the ratio of Mn3+/Mn4+ increases on the surface of LSMO film annealed in vacuum comparing with the as-prepared film, though the saturation magnetization (Ms) changes little. Mn6+ and Mn7+ can be detected while Mn4+ decreases much on the surface of LSMO film annealed in oxygen. The change of Mn3+/Mn4+ results in the obviously reduce of Ms. O1s spectra show the gradual changes of Mn-O, Sr-O and La-O. Analysis indicates that Mn2+ forms at the surface defects of LSMO films. Annealing in vacuum hardly affects the magnetic property of LSMO films. But annealing in oxygen greatly changes the valence states of Mn, which weakens the magnetic property of LSMO films.

Down graded barium strontium tianate(BST) thin films were prepared on Pt/Ti/SiO2/Si(100) substrate by radio frequency magnetron sputtering. The BST thin films were deposited at various substrate temperatures, then annealed at 700 °C for an hour. The influences of the deposition parameters on the crystallization behavior, microstructure and dielectric properties of BST thin films were investigated by X-ray diffraction, field emission scanning electron microscopy and dielectric frequency spectra. XRD results indicate that the BST thin films deposited at higher temperature have improved crystallization structure.The SEM observations show that the surface of the films is smooth with homogeneous grains.The dielectric properties of the films have been examined and discussed. The experiments show that BST thin films deposited at 650oc, 3.0Pa working pressure exhibits superior dielectric properties: the highest dielectric constant is 448 and lowest dielectric loss is 0.013 at 100 kHz, respectively. These results make BST thin films be a promising candidate for microelectronic device application.

Ba0.8Sr0.2TiO3(BST) thin films with different Nd-doped concentrations have been frabracated on silicon substrates by modified Sol-gel process. All the samples were annealed at 700°C for 60 min.The structural and morphological properties of the films were examined by X-ray diffraction (XRD) and Atomic Force Microscopy (AFM). The XRD studies indicated that both pure and doped BST thin films show crystallized perovskite structures, the particle size is about 20 nm. The AFM images displayed that the films have high quality and finegrained polycrystalline structure. The photoluminescence spectra(PL) were carried out using the 808 nm Ar+ laser line as the excitation source at room temperature. The Nd-doped BST thin films show three NIR luminescence peaks corresponding to 4F3/2-4I9/2 transition at 880 nm; 4F3/2-4I11/2 transition at 1066 nm and 4F3/2-4I13/2 transition at 1345 nm; respectively. The influence of Nd3+ concentration on the microstructure and the luminescence properties were discussed. All the results showed that the Nd-doped BST films have great potential uses for novel integrated optic devices.

Amorphous GeS6 bulk glass and film were prepared by the traditional melt–quenching method and pulsed laser deposition technique. The optical transmission spectra, absorption spectra and Raman spectra were measured. The short- wave absorption edges were described using the ‘non–direct transition’ model proposed by Tauc. And the optical band gaps of the bulk glass and film were derived from the absorption spectra. The results show that GeS6 film has bigger optical band gap than that of bulk glass. The structural units of the bulk glass and film were characterized using Raman spectroscopy. In addition to the basic structural units of edge-sharing and corner-sharing GeS4/2 tetrahedra, there are S–S homo–polar bonds in both GeS6 bulk glass and GeS6 film. While more S8 rings exist in GeS6 bulk glass. The bigger optical band gap of the GeS6 film was discussed in relation to the structure of the film confirmed by the Raman spectra analysis.