The effects of the barium/titanium (Ba/Ti) ratio on the crystalline phase, Curie temperature, and dielectric properties of solid-state-reacted BaTiO3 powder were investigated. The experimental results showed that tetragonality decreased and the Curie temperature shifted to lower temperature when the Ba/Ti ratio strayed from 1.0. The BaTiO3 powder had the maximum dielectric constant when the Ba/Ti approaching 1.0.

Phase structures and electrical properties of lead-free piezoelectric (1−x)(Bi0.5Na0.5)TiO3–x(K0.5Na0.5)NbO3 (BNT–xKNN) ceramics with 0.08 ≤ x ≤ 0.19 were systematically investigated. Results showed that a phase transition from a tetragonal to a pseudocubic phase occurred in this system, as KNN content increases. The addition of KNN shifted both the depolarization temperature Td and rhombohedral–tetragonal phase transition temperature TR-T to lower temperatures and tended to enhance the relaxor behavior of the ceramics, which was well explained by the microdomain–macrodomain transition theory with calculating criterion K. At x = 0.10–0.11, Td reached room temperature (RT), which accordingly induced an enhancement of the unipolar strain that peaks at a value of 0.22% was obtained. Furthermore, as the compositions (x = 0.12–0.15) have Td below RT, samples exhibited high electrostrictive response with large electrostrictive coefficient Q33 (0.017–0.019 m4/C2) and good thermostability comparable with that of traditional Pb-based electrostrictors.

A series of layered n-ABO3-doped Aurivillius structures Bi4Ti3O12 (BTO) thin films are synthesized on (001) SrTiO3 (STO) substrates by pulsed laser deposition, where n represents the number of ABO3 perovskite. X-ray diffraction substantiates that these films have expected layered Aurivillius structures. Furthermore, the microstructure of these samples is “systematically” characterized by transmission electron microscopy. It is found that the structure of n-STO-doped BTO becomes unstable when n is equal to 3, as revealed by the occurrence of intergrowth. Similar phenomenon is observed in n-LaFeO3-doped BTO; the layered Aurivillius structure is totally collapsed in the case of n as high as 2.5. In contrast, 3-BiFeO3-doped BTO still keeps perfect Aurivillius structure. The above-observed structural stabilities of these materials are explained by the theoretical formation enthalpy calculated by the density functional theory. This work provides the necessary information to explore the multifunctionality based on Aurivillius n-ABO3–BTO oxides.

The effect of Mn incorporation into lead titanate (PbTiO3, abbreviated as PT) host lattice is being studied, and the corresponding variation with regard to tetragonality, radiative emission, and ferroelectric response is highlighted. The Mn doping has a weak dependency on the average crystallite size and is found to be within 34–39 nm for both Mn-free and Mn-included PT nanostructures. The tetragonality (c/a ratio) is found to increase with Mn level thus giving a maximum value of 1.061 for 10% Mn doping (Mn/Ti = 0.1). Further, a prominent splitting of (001) and (100) peaks in the diffractograms confirms the tetragonal characteristics of PT nanosystem. Apart from the luminescence peaks due to direct electron deexcitation and the localized states observable in the violet and blue regimes, the association of Mn2+-related orange–red emission (λ = 580 nm) was observed for Mn-incorporated PT systems. The P-E hysteresis trace exhibited a minimum tilting of ∼28° for a system that contained 10% Mn level. As a consequence of polarization switching, the effect of Mn content on remnant polarization and critical field is discussed in the light of domain wall motion and depolarization field due to surface dielectric layers. The injection of magnetic ions into nanoscale ferroelectrics is promising, which would bring insight to the understanding of charge–spin interactions for application in polarization reversal/switching elements.

Comparisons of structural, optical, and magnetic properties between KY(WO4)2 (KYW) powders doped with Gd3+ from 0.5 up to 100 mol% and KGd(WO4)2and KYW single crystals have been made. For this purpose, x-ray diffraction (XRD), infrared (IR), Raman, and electron paramagnetic resonance (EPR) spectra were collected. The XRD studies have verified the quality of the synthesis of compounds and have shown the differences in the positions of the diffraction peaks due to the change in concentration of gadolinium ions. Raman and IR spectra confirmed that the phases are isostructural. The optimization of the spin Hamiltonian parameters and EPR data simulation was achieved by using the electron paramagnetic resonance and nuclear magnetic resonance (EPR-NMR) program. Changes in kind of magnetic interactions were found and analyzed from the point of view of their dependence of the compound form (powder, single crystal), temperature, and gadolinium ion concentration. The investigated compounds revealed complex interactions between gadolinium ions both in a type and a strength.

To possess the merits of both building blocks, i.e., the rapid interfacial electron transport of ZnO nanoneedles (NNs) and the high surface area of TiO2 nanoparticles (NPs), the ZnO NN and TiO2 NP composite photoelectrodes were prepared with controllable weight ratio. The dye-sensitized solar cell (DSSC) prototypes were fabricated based on this composite photoelectrodes, and the photoelectrical properties have been systematically studied. The results indicate that the composite cells achieve higher power conversion efficiency compared to pure TiO2 NP cells by rational tuning the weight ratio of ZnO NNs and TiO2NPs. The DSSC with 1 wt% ZnO NNs yields the highest η of 5.16%. It is elucidated by the interfacial electron transfer of DSSC with different weight of ZnO NNs using the electrochemical impedance spectra. And it is found that the DSSC with 1 wt% ZnO NNs displays the fastest interfacial electron transfer.

Through a polyethylene-glycol-assisted hydrothermal method, a series of potassium fluoride (KF)–Yttrium (III) fluoride (YF3) system materials have been synthesized. By controlling the reactant ratios of KF: rare earth ions (RE3+), the hydrothermal temperatures, and the pH values of the prepared solutions, the final products can evolve among the orthorhombic phase of YF3 and/or the tetragonal phase of potassium triyttrium decafluoride (KY3F10) and/or the cubic phase of potassium yttrium tetrafluoride (KYF4). The final products are characterized by the x-ray diffraction (XRD) patterns, the field-emission scanning electron microscopy (FE-SEM) images, the energy-dispersive spectroscopy (EDS) patterns, the photoluminescence (PL) spectra, and the luminescent dynamic decay curves. The XRD patterns of the samples suggest the phase evolution of the final products. The FE-SEM images and the EDS patterns prove that. Europium ion (Eu3+) acting as a probe, its PL spectra and the luminescent decay curves all put together prove the phase evolution of the final products. The research can be extended to study the other KF–REF3 system materials.

The preparation of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BmImTFSI)-based poly(methyl methacrylate)–poly(vinyl chloride), PMMA–PVC, gel polymer electrolytes was done by solution casting technique. The ionic conductivity of gel polymer electrolytes was increased, up to a maximum value of (1.64 ± 0.01) × 10−4S/cm by adding 60 wt% of BmImTFSI. Conductivity–frequency dependence, dielectric relaxation, and dielectric moduli formalism were also further analyzed. These studies assert the ionic transportation mechanisms in the polymer matrix. Occurrence of polarization electrode–electrolyte interface is also observed. This leads to the formation of electrical double layer and hence indicates the non-Debye characteristic of the polymer matrix in the dielectric studies. Based on the changes in shift, changes in intensity, changes in shape, and existence of new peaks, attenuated total reflectance–Fourier transform infrared divulged the complexation between PMMA, PVC, lithium bis(trifluoromethanesulfonyl)imide, and BmImTFSI, as shown in the infrared spectra.

One-dimensional (1D) nanofibers of polypyrrole (PPY) are fabricated on glass substrates in the presence of different dopants, namely, hydrochloric acid (HCl), ferric chloride (FeCl3·6H2O), p-toluene sulfonic acid, camphor sulfonic acid, and polystyrene sulfonic acid using a simple in situ vapor phase chemical oxidative polymerization method. Preliminary morphological details investigated using light microscopic study reveal 1D configuration for all the doped PPY structures, indicating a fibrous/tubular appearance. Furthermore, scanning electron microscopy confirms preferential growth of these PPY structures as fine fibers arranged in a brush-/comb-like pattern, having an average diameter of 70 nm. Such brush-like growing pattern observed for the PPY nanostructures without the aid of nanoporous membranes and/or sophisticated techniques is not very commonly reported in the literature. The undertaken work suggests applications of nanodimensioned fabricated PPY structures in the practical nanodevices and/or functional glass for sensing, optoelectronic, photocatalysis, and solar energy systems.

Concentrated electric field is crucial in generation of needleless electrospinning; the electric field profile together with electric field intensity of the spinneret directly affect the needleless electrospinning performance. Understanding the electric field of different spinnerets would definitely benefit the design and optimization of needleless electrospinning. Three-dimensional (3D) finite element analysis has been used to analyze the electric field profile and electric field intensity of different spinnerets for needleless electrospinning by using the simulation software COMSOL Multiphysics 3.5a. It has been found that evolution of the spinneret of needleless electrospinning from cylinder to multiple disks and then to multiple rings results in stronger and more concentrated electric field. The analysis based on 3D simulation of the electric field could benefit further development of needleless electrospinning in which the production rate and quality of as-spun nanofibers are of great importance.

This paper shows a comparison between different nanostructured oxides, obtained by polymeric precursor method, regarding their activity for biodiesel conversion from oil–methanol mixtures. The basicity/acidity and surface area (SA) of the oxides were taken in account to analyze the catalytic activity in the transesterification reaction. The temperature dependence for the heterogeneous catalysts was analyzed, where only CaO showed activities at 70 °C (∼98% of conversion), while the other oxides, SnO2, ZnO, TiO2, CaTiO3, were observed active only at 150 °C for the reaction parameters adopted. The results revealed that the highest activity observed is not associated to SA only but mainly with the surface basicity. This suggest that, for oxides synthesized by the polymeric precursor method, the surface basicity surpasses the particle size effects in catalysis in a way to promote the transesterification reaction.

Nitrogen (N) and boron (B) codoped diamond-like carbon (DLC) films were prepared on silicon oxide substrates by RF magnetron sputtering to optimize the electrical conductivity and hardness of DLC film. The electrical conductivity and hardness of the N–B codoped DLC films were controlled simultaneously by varying N2 flow rate with fixed B target power and varying B target power with fixed N2flow rate. The electrical resistivity of the B-doped DLC films showed a cup-shaped relationship with B target power and a U-shaped relationship with the N–B codoped DLC film. However, hardness of the B-doped DLC films showed a decreasing behavior but it was maintained almost constant for the N–B codoped DLC film. These particular electrical and hardness behaviors of the N–B codoped DLC films could be explained by a neutralization effect of N and B codoping.

A new technique for micropatterning Fe-based bulk metallic glass surfaces is reported. The transpassive dissolution process is utilized for a defined localized material removal when using a pulsed electrochemical micromachining process. By applying submicrosecond pulses between a work piece and a tool electrode, microholes of high aspect ratio and depth of up to 100 μm can be machined into the bulk glassy Fe65.5Cr4Mo4Ga4P12C5B5.5 alloy. Two potential electrolytes are identified for the machining process. For these electrolytes, different reaction mechanisms are discussed. The possibility of machining more complex structures is demonstrated for the most promising electrolyte, a methanolic H2SO4solution. The impact of the process parameters, pulse length and pulse voltage, on the machining gap and the surface quality of the machined structures is evaluated.

Quasicrystalline precipitates in ZrAlNiCuNb alloy were systematically studied by transmission electron microscopy. It was found that precipitates always contain various linear phason strains. By electron diffraction analysis, two types of linear phason strain with two different directions perpendicular to the incident beam described by strain matrices with only one nonzero element were identified. After measuring the deviations of diffraction spots and quantitatively fitting against their perpendicular components of the reciprocal lattice vectors, the phason strain matrices were obtained. Domain structures formed as a result of linear phason strain variants along directions with equal probability. Electron diffraction and high-resolution electron imaging provide supportive evidence of this result.