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A method for achieving the accurate measurement of the antiferroelectric-ferroelectric (AFE-FE) phase switching time based on the electrically induced light scattering effect was designed. The AFE-FE switching times of lanthanum-modified lead zirconate titanate (PLZT) transparent ceramics decreased with the increase of the applied electric fields, and the logarithm of the switching time was approximately proportional to the electric field reciprocal. The random orientation of the polycrystalline structures with dispersion-distributed mixed phases of the PLZT transparent ceramics was the intrinsic mechanism affecting the corresponding switching times in the applied electric field. The smaller electrode size samples switched faster than the larger samples in the same electric field. The size effect of the switching times occurred due to the higher dielectric constant of the ceramics and the parameters of the test circuit, and the larger capacitance of the samples resulted in a longer rising time of the applied electric field, which in turn slowed down the phase switching and prolonged the switching time.

Luminescent inorganic perovskite nanocrystals (PeNCs) are promising in various optical applications, particularly in advanced lighting and displays. The instability of PeNCs and PeNC composites from different aspects hinder their practical applications. Many previous methods indicate that an intact and facile wrapping strategy could effectively address this challenge. In this work, we introduce an in situ ligand polymerization (ILP) method for the fabrication of PeNC composites. By introducing (3-aminopropyl)triethoxysilane (APTES) as the initial ligand of the PeNCs directly and polymethylhydrosiloxane (PMHS) as the monomer to form the polymerized matrix, a polymerized and hydrophobic SiO2 matrix structure is formed, which intrinsically protects the PeNCs against moisture-induced deterioration. The stability test indicates that the ILP composite powders demonstrate an improved stability against various solvent conditions and light exposure compared to the conventional PeNCs–SiO2 composite. More importantly, the ILP composite exhibits an excellent compatibility with the acrylate solvent which is widely used for light-solidification in light converting film fabrication. The ILP composite film demonstrates an ultrastable operational performance in our standard test outperforming the conventional PeNCs–SiO2 composite configuration. Thus, the ILP composite demonstrates great potential for use in advanced lighting and displays.

Deep-red luminescence emission makes CsPbI3 nanocrystals (NCs) promising materials for various applications, but their use is limited in practice by instability in moist ambient environments. Incor...

Low-dimensional lead-free metal halides, which feature strong quantum confinement effects, have recently attracted great attention due to their excellent optical properties and favorable stability under ambient conditions. Although controllable synthetic strategies, structural characterization and linear optical properties of lead-free metal halides have been widely reported, relevant studies on their nonlinear optical properties are still lacking, which hinders their applications in nonlinear photonic devices. Herein, two types of millimeter-level high-crystallinity cesium copper halide single crystals (SCs), i.e., Cs3Cu2I5 and CsCu2I3, with high photoluminescence (PL) quantum yields, are synthesized using an antisolvent vapor-assisted crystallization method. Their phonon energies are comparatively studied by using Raman spectroscopy and temperature-dependent PL spectroscopy. More importantly, comparison studies of the multiphoton absorption (MPA) properties of Cs3Cu2I5 and CsCu2I3 SCs are performed for the first time. Strong multiphoton excited PL emissions with large anisotropy factors are observed in these two types of SCs. Through the measurement of nonlinear transmittance, it is found that CsCu2I3 SCs exhibit much larger MPA coefficients compared with Cs3Cu2I5 SCs, which is attributed to the larger density of states in the former. This work broadens the applications of cesium copper halides in nonlinear optoelectronics and light polarization related devices.

Based on the extensive investigation on graphene and graphene derivatives asymmetrically functionalized with a variety of molecular groups and the concept of Janus materials with asymmetric facial properties, Janus two-dimensional (2D) materials as derivatives of the 2D material family, including Janus graphene, Janus transition metal chalcogenides, etc., have attracted much attention in recent years. Janus 2D materials have been demonstrated experimentally and theoretically to possess unique properties such as an out-of-plane piezoelectric polarization and strong Rashba effect due to their out-of-plane asymmetry. Here, the recent progress of emerging Janus 2D materials, including Janus graphene, prediction and fabrication of various different Janus 2D materials and Janus 2D van der Waals heterostructures, is presented. The investigations on the unique properties and potential device applications of Janus 2D materials are summarized. Finally, the conclusion and prospects for the future explorations on Janus 2D materials are also provided.

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.

Structural symmetry plays a crucial role in the electronic band structure and properties of two-dimensional materials. In contrast to graphene, monolayer transition metal dichalcogenides exhibit intrinsic in-plane asymmetry with suitable direct bandgaps and distinctive optical properties. Efforts have been devoted to breaking their out-of-plane mirror symmetry by applying external electric fields, vertical stacking, or functionalization. The successful fabrication of Janus transition metal dichalcogenides offers a synthetic strategy to breaking the vertical mirror symmetry, leading to a variety of novel properties, such as vertical piezoelectricity, Rashba spin splitting, and excellent exciton properties. Here, we discuss the universal fabrication approaches and unique properties of Janus transition metal dichalcogenides and further present a brief perspective on their potential applications and challenges.

Hybrid organic-inorganic metal halides have emerged as highly promising materials for a wide range of applications in optoelectronics. Incorporating chiral organic molecules into metal halides enables the extension of their unique optical and electronic properties to chiral optics. By using chiral (R)- or (S)-methylbenzylamine (R-/S-MBA) as the organic component, we synthesized chiral hybrid copper halides, (R-/S-MBA)2 CuCl4 , and investigated their optical activity. Thin films of this material showed a record anisotropic g-factor as high as approximately 0.06. We discuss the origin of the giant optical activity observed in (R-/S-MBA)2 CuCl4 by theoretical modeling based on density functional theory (DFT) and demonstrate highly efficient second harmonic generation (SHG) in these samples. Our study provides insight into the design of chiral materials by structural engineering, creating a new platform for chiral and nonlinear photonic device applications of the chiral hybrid copper halides.

In recent years, it has witnessed a rapid development of the fluorescent carbon dots (CDs) due to their unique optical properties and wide range of applications. However, difficulties in synthesizing long wavelength-emitting CDs have been the major drawback of CDs, which limited their applications in fields such as bioimaging and carbon-based white light-emitting diodes. Herein, on the basis of surface electron state engineering, we prepared surface metal-ion-functionalized CDs by treating solvothermally synthesized CDs with alkali metal aqueous solutions (LiOH, NaOH or KOH). Especially, we focused the CDs treated with LiOH solution (Li-CDs) because these CDs’ absolute photoluminescence quantum yield is as high as 34% in dilute ethanol solution under 550 nm excitation compared with those treated with NaOH or KOH solutions. The electron transport effect of alkali metal ions was confirmed. Moreover, the obtained Li-CDs show high optical pH sensitivity within pH values 1–4.5 and were applied to pH sensing. This work not only proposes a feasible and controllable method to construct long wavelength-emitting CDs, but also shows the application potentiality such as pH sensing devices.

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.

Relaxor ferroelectrics have been widely used in dielectric, pyroelectric, electric field modulation microwave devices and electrostriction device. These applications refer to effect of electric field, increase in strength of polarization from ferroelectric phase stretching to paraelectric phase successively, to give rise to an effect similar to field induced effect. A result of the peak temperature of dielectric permittivity changing with the electric field 2/3 power was obtained by using approximation method, which is coincident with the experimental result of dielectric peak. The numerical simulation results found that there exist a thermal dynamics related polarization-temperature coefficient. Increasing the coefficient will decrease shift effect of dielectric peak, or will decrease effect of field induced phase transition, but, will increase pyroelectric effect. On the contrary, the stronger shift effect of dielectric peak will increase dielectric tunability and its temperature stability for electric field modulated microwave devices. The above theoretic results have certain reference implications for dielectric tunability of microwave device and pyroelectric property by doping modification method.

Perovskite nanocrystals (PeNCs) are attractive in high-color gamut display technology as light converters which can achieve saturated green and red lights, respectively. However, PeNCs are intrinsically fragile against ambient conditions, such as moisture and oxygen and it is hard to maintain their performance in long-term operation. In this work, a new hierarchical encapsulation method is proposed, integrated with surface modification by halide ions protection, nano-scaled encapsulation by in situ capping SiO2 and embedding into poly (methyl methacrylate) (PMMA) matrix composites, to achieve a stable perovskite light converting composite sheet for LED remote-type encapsulation. The storage stability, as well as the operational stability of perovskite composites, were confirmed by the spectra evolution from encapsulated LEDs with normalized blue emission intensity. The 2D maps of spectra and aging measurement indicate that the silica encapsulation can well protect the PeNCs in the PMMA matrix from the ambient circumstance during a long-term storage process. Additionally, the hierarchical encapsulation for PeNCs/silica/PMMA showed better operational stability than the direct encapsulation of PeNCs/PMMA, and the correspondent Commission Internationale de L'Eclairage color coordinates tracking also indicated more stable color properties, which demonstrates the great potential in photoluminescent display applications.

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.

A method based on the Stokes vectors was developed for the measurement of electro-optical (EO) coefficients, and the detailed test principle, experimental apparatus and data processing were described. The practicability of this method was illustrated by the determination of the EO coefficient of lanthanum-modified lead zirconate titanate (PLZT) transparent ceramics, and the measurement results indicated that the standard deviation values of the EO coefficients obtained by the Stokes vector method was almost half of that of the values measured using the Senarmont compensator method. The apparatus used for the Stokes vector method consists of only a few optical elements and was easy to adjust and calibrate, thereby enabling scientific, accurate, and efficient EO coefficient measurements for the development of EO materials and devices.

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.

Transition metal oxides (TMOs) consist of a series of solid materials, exhibiting a wide variety of structures with tunability and versatile physicochemical properties. Such a statement is undeniably true for chiral TMOs since the introduction of chirality brings in not only active optical activities but also geometrical anisotropy due to the symmetry-breaking effect. Although progressive investigations have been made for accurately controlled synthesis and relevant explanations on the chirality origin of such materials, the overall field of chiral TMOs is still in its infancy with adequate space for interdisciplinary communications and development. Herein, therefore, recent advances in both experimental phenomena and theoretical calculations in this area are reviewed, to elucidate the underlying chiral origin with respect to their fabrications process, triggering new insights for further evolution of this field.

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.

Due to their unique optoelectronic properties, doped semiconductor nanocrystals (NCs) are promising fluorescent probes for deep-tissue bioimaging applications. However, studies on the photophysical properties of cadmium-free doped NCs are scare. In this study, we synthesized and studied the photophysical properties of one type of cadmium-free doped NCs (Cu: ZnInS/ZnS NCs), which exhibit near infrared-I (NIR-I) emission at 730 nm and long emission lifetime up to 1.38 μs. Femtosecond transient absorption spectra revealed a strong exciton coupling effect between the Cu2+ ions and the ZnInS/ZnS host, with a fast energy transfer time of ≈100 ps. More importantly, Cu: ZnInS/ZnS NCs exhibit efficient volume-normalized two- and three-photon absorption cross-sections in NIR-I (800-900 nm) and NIR-III regions (1600-1990 nm), with maximum values up to 6.9 GM nm-3 at 800 nm and 1.1×10-80 cm6 s2 photon-2 nm-3 at 1600 nm, respectively. This study can shed light on the exploration of novel environmentally friendly doped NCs for deep-tissue bioimaging applications.

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).

100-nm-thick epitaxial BaTiO 3 (BTO) films were prepared on the Nb-doped SrTiO 3 (NSTO) single-crystal substrates by pulsed laser deposition. Bipolar resistive switching (RS) behavior was observed in the as-prepared BTO/NSTO samples, which was attributed to the formation and rupture of conductive filaments in the BTO films. The RS effect was suppressed after the samples were annealed in air due to the decrease in oxygen vacancies during annealing, which was confirmed by X-ray photoelectron spectroscopy (XPS) measurements. The current–voltage curves of the as-prepared samples show linear ohmic conduction at the low resistive state and space-charge-limited conduction (SCLC) at the high resistive state, respectively. SCLC dominated in the annealed samples.

The effect of ZrO2 content on the performance of vitrified bond was discussed. The results showed that when the ZrO2 content was less than 2 mol%, Zr4+ could enter into the glassy network as mending nets and agglomeration composition. In this case, with the increasing of ZrO2, the vitrified bond’s bending strength increased and the expansion coefficient decreased. It was also found that the wetting angle between the vitrified bond and diamond got small because Zr4+ was enriched on diamond surface. When ZrO2 content was more than 2 mol%, a part of ZrO2 existing in vitrified bond as ZrO2 particles played the role in nucleating agents and promoting the separation of spodumene. When ZrO2 content was 3 mol%, the bending strength of the vitrified bond reached its maximum of 128 MPa and the wetting angle with the diamond reached its minimum of 37.6°.

Amorphous GeSex (x = 2, 4, 6) films were prepared by pulsed laser deposition technique. The optical band gaps ( E g opt ) and refractive indices of the films were derived from the absorption spectra and optical transmission spectra, respectively. The short-wave absorption edges of the films were well consistent with the ‘non-direct transition’ model proposed by Tauc. The dispersion of the refractive index was analyzed in terms of the single-oscillator Wemple–Di Domenico model. The structural units of the films were characterized using Raman spectroscopy. In addition to the basic structural units of edge-sharing GeSe4/2 tetrahedra, there are Se Se homopolar bonds in Se-rich GeSe4 and GeSe6 films. And Ge Ge bonds exist in stoichiometric GeSe2 film. The results also show that the refractive index of the films changes with the Se content. E g opt decreases with the reduction of Se content in the GeSex films. The changes of E g opt were discussed in relation to the structures of the films confirmed by the Raman spectra analysis.

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.

CdSe/CdS semiconductor quantum dots co-sensitized TiO2 nanorod array was fabricated on the transparent conductive fluorine-doped tin oxide (FTO) substrate using the hydrothermal and successive ionic layer adsorption and reaction (SILAR) process. The structural and morphological properties of the samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The results indicate that CdSe/CdS QDs are uniformly coated on the surface of the TiO2 nanorods. The shift of light absorption edge was monitored by taking UV-visible absorption spectra. Compared with the absorption spectra of the TiO2 nanorod array, deposition of CdSe/CdS QDs shifts the absorption edge to the higher wavelength. The enhanced light absorption in the visible-light region of CdSe/CdS/TiO2 nanorod array indicates that CdSe/CdS layers can act as co-sensitizers in quantum dots sensitized solar cells (QDSSCs). By optimizing the CdSe layer deposition cycles, a photocurrent of 5.78 mA/cm2, an open circuit photovoltage of 0.469 V and a conversion efficiency of 1.34 % were obtained under an illumination of 100 mw/cm2.

CdSe quantum dots (QDs) were introduced as an interlayer in the poly(3-hexylthiophene)(P3HT)/TiO 2 nanorod arrays (NRAs) hybrid solar cells. The presence of CdSe QDs was found to provide enhanced light absorption, assisting charge separation at the P3HT/TiO 2 interface, and leading to a lower recombination rate of the electrons due to the stepwise structure of band edge in P3HT/CdSe/TiO 2 , which accounts for the observed enhanced photocurrent and photovoltage of the hybrid solar cells. As a result, the efficiency of P3HT/CdSe QDs/TiO 2 NRAs hybrid cell is greatly higher than that of P3HT/TiO 2 NRAs based cell.

The 80-nm-thickness BaTiO 3 (BT) thin film was prepared on the Pt/Ti/SiO 2 /Si substrate by the RF magnetron sputtering technique. The Pt/BT/Pt/Ti/SiO 2 /Si structure was investigated using X-ray diffraction and scanning electron microscopy. The current–voltage characteristic measurements were performed. The bipolar resistive switching behavior was found in the Pt/BT/Pt cell. The current–voltage curves were well fitted in different voltage regions at the high resistance state (HRS) and the low resistance state (LRS), respectively. The conduction mechanisms are concluded to be Ohmic conduction and Schottky emission at the LRS, while space-charge-limited conduction and Poole–Frenkel emission at the HRS. The electroforming and switching processes were explained in terms of the valence change mechanism, in which oxygen vacancies play a key role in forming conducting paths.

Ho3+ doped Ba0.65Sr0.35TiO3 (BST) nanocrystals was prepared by sol–gel method. The structural and morphological properties of the nanocrystals were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The absorption spectrum, photoluminescence spectrum and fluorescence time decay curve were measured at room temperature. Based on the Judd–Ofelt (J–O) theory, the J–O intensity parameters Ωt (t=2, 4, 6) of Ho3+ doped BST nanocrystals were calculated to be 0.67×10−20 cm2, 1.11×10−20 cm2 and 1.09×10−20 cm2, respectively. The emission probabilities, radiative lifetimes and branching ratios of the different Ho3+ transitions were also determined. The emission cross sections of the important intermanifold transitions 5F4, 5S2→5I8, 5F5→5I8 and 5F4→5I7 have been calculated from the luminescence spectrum. The room temperature fluorescence lifetime of the 5S2→5I8 transition for Ho3+ in BST nanocrystals was measured and the radiative quantum efficiency was estimated to be 61.9%.

Tm-doped Ba 0.8 Sr 0.2 TiO 3 thick films were prepared by the screen-printing technique on the alumina substrate. The microstructure of the Tm-doped BST thick films was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy, respectively. All the samples showed a typical perovskite polycrystalline structure when sintered at 1260 °C. The substitution behavior of Tm 3+ ion in BST was found to change with increasing the Tm 3+ concentration. The observed Tm-related red emission reaches the maximum at 0.2 mol% Tm 3+ concentration. The effects of concentration quenching on the luminescence intensity were discussed.

Amorphous GeS x (x = 2, 4, 6) films were prepared by the pulsed laser deposition (PLD) technique. The optical band gaps ( E g opt ) and refractive indices of the films were obtained from the optical absorption spectra and transmission spectra, respectively. The short-wave absorption edges of the films were described using the ‘non-direct transition’ model proposed by Tauc. The dispersion of the refractive index was analyzed in terms of the single-oscillator Wemple–Di Domenico model. The structural units of the films were characterized using Raman spectroscopy. In addition to the basic structural units of edge-sharing and corner-sharing [GeS 4 ] tetrahedra, there are S–S homopolar bonds in S-rich GeS 4 and GeS 6 films while Ge–Ge bonds exist in stoichiometric GeS 2 film. The results show that the index of refraction decreases while E g opt increases with the sulphur content in the GeS x films. The changes of E g opt were discussed in relation to the structure of GeS x films, which were confirmed by the Raman spectra analysis.

Ba0.8Sr0.2TiO3 ceramics were prepared by the conventional solid-state reaction method. The effects of different calcining and sintering temperatures on pyroelectric properties of the ceramics were investigated. The TG-DTG test was used to determine the calcining temperature. The XRD results showed that all samples were perfect perovskite structure. SEM results exhibited a homogeneous grain dimensions distribution and dense microsructure in the samples prepared for optimum process condition. The dielectric constant and dielectric loss of Ba0.8Sr0.2TiO3 ceramics are 1681 and 0.0067 at 100 kHz in room temperature, respectively. The pyroelectric coefficient is 4542 μC·m−2·K−1. The mean detection rate (FD) reached 1.42 × 10−4 m3/2·J−1·F−1/2.

Amorphous (GeSe2)100−x –Bi x (x=0, 0.4, 2 and 4) films were prepared by the pulsed laser deposition technique. The optical transmission spectra, absorption spectra and Raman spectra of the films were measured. The short-wavelength absorption edges in the strong absorption region of the films were described using the ‘non-direct-transition’ model proposed by Tauc and the optical band gaps (\(E_{\mathrm{g}}^{\mathrm{opt}})\) were determined. The Urbach energy (E u) was derived in the exponential part of the absorption edge. Both \(E_{\mathrm{g}}^{\mathrm{opt}}\) and Tauc slopes (B 1/2) decreased with increasing Bi content, while E u had the opposite trend. The refractive indices of the films were calculated from the transmission spectra by using the Swanepoel method. Analysis of Raman spectra and absorption spectra shows that Bi addition decreases the mean bond energy and increases E u in the amorphous films, which caused the decrease of \(E_{\mathrm{g}}^{\mathrm{opt}}\). The changes of the refractive indices are also discussed.

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.