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In this work, the role of oxygen vacancy on the electrical properties of traditionally prepared SnO 2 -Zn 2 SnO 4 ceramic composites was evaluated by introducing Nb 2 O 5 oxide. With increasing Nb 2 O 5 content, the breakdown electric field E 1.0 and the relative permittivity e r measured at low frequencies increased and declined, respectively. In the microstructure photos, the grain size decreased before reaching a saturation point. In addition, Nb was randomly distributed in the grains and along grain boundaries. By doping Nb 2 O 5 , the color of the sintered samples darkened, and F-type color centers were generated. In the complex electric modulus spectra, the peak of the imaginary part M ″ shifted toward a lower frequency; whereas, the activation energy E a changed slightly with increasing Nb 2 O 5 content. The results suggest that oxygen vacancy is the origin of the varistor and high permittivity properties of SnO 2 -Zn 2 SnO 4 ceramic composites. Furthermore, the varistor and dielectric properties can be modulated by changes in the microstructure.

The structural, leakage current, ferroelectric and magnetic studies of the co-doped SPTFx (x=0.1, 0.2 and 0.3) films have been investigated. X-ray diffraction and atomic force microscopy reveal the microstructure of the samples. It is found that the dc leakage currents of the films are enhanced gradually with increasing Fe ions due to the variable valence of Fe ions and the increase of oxygen vacancies (OVs). More importantly, both the room-temperature ferroelectric and ferromagnetic properties are successfully realized in STO films, whose possible causes are discussed. This work provides an effective method for the induction of the multiferroic properties in paraelectric materials.

High purity and yield of ZnO nanobelts, nanocombs and nanowires have been synthesized using a simple catalyst-free vapor transport process and their growth mechanism and photoluminescence properties have been investigated. Transmission electron microscopy and selected-area electron diffraction analyses reveal that the intrinsic growth behaviors of ZnO vary with the growth temperature, leading to the formation of nanostructures with different morphologies. These ZnO nanostructures show a UV emission at about 385 nm and a broad green emission around 500 nm in their photoluminescence spectra, and the green to UV emission intensity ratio is determined by their microstructures.

Lead-free (Na0.65K0.35)NbO3 + x wt.% Co2O3 (KNN–xCo) piezoceramics were synthesized by conventional ceramic processing and the effects of low Co2O3 concentration on the microstructure and electrical properties were investigated. The experimental results show that the orthorhombic–tetragonal phase transition temperature (TO–T) decreases slightly whereas the tetragonal–cubic phase transition temperature (TC) and crystal structure keep unchanged with the increasing of Co2O3 content. The doping of Co2O3 facilitates the grain growth and improves the density and piezoelectric properties of the ceramics. The sample of x = 0.2 exhibits good piezoelectric properties of piezoelectric coefficient d33 = 127pC/N and electromechanical coupling coefficient kp = 35.1% with density of ρ = 4.31/cm3. These results strongly suggest that the composition of (Na0.65K0.35)NbO3 is another promising lead-free candidate for investigation besides (Na0.5K0.5)NbO3 system.

Expanded leaf-roots of tobacco are used as fillers into cigarette products to reduce cost and contents of tar and nicotine and improve quality. To study the difference between expanded and original leaf-roots of tobacco, terahertz (THz) time-domain spectroscopy was used to detect the absorption spectra in the frequency range from 0.2 to 1.5 THz. Significant difference in terahertz absorption was observed in original and expanded leaf-roots. To understand the origin, scanning electron microscope was employed for microanalysis, revealing the difference in element compositions and surface appearances between original and expended leaf-roots. Non-polar and low-polar components of leaf-roots were largely lost after dissolving into liquid CO2 during expansion, accounting for the difference in THz absorption spectroscopy.

ZrO2 dielectric films were deposited on Si substrates by reactive magnetron sputtering technique. Interfacial and optical properties were investigated. Crystal structure was studied by X-ray diffraction. Fourier Transform Infrared Spectroscopy analysis confirmed the presence of a low-k interfacial SiO2 layer due to the excited oxygen radicals in the sputtering plasma and the physisorbed oxygen in as-deposited ZrO2 films. Optical constants were extracted based on the best spectroscopic ellipsometry fitting results. Absorption coefficients near the absorption edge were also calculated. The absorption tails in the range 4.5–4.75 eV indicated that there was a defect energy level below the conduction band of ZrO2 due to oxygen vacancies.

The electrical properties of (Nb, Zn)-doped SnO2 ceramics as an new varistor material were investigated. It was found that there exists a correlation between the nonlinearity of the current density versus the electrical field, the frequency properties of relative permittivity and resistivity. Samples doped with 1.0 mol% ZnO and 0.05 mol% Nb2 O5 , which possess a comparatively low dielectric constant and the highest resistivity of all of the samples investigated, exhibits a higher nonlinear coefficient than the other samples. A defect barrier model for ZnO-based varistor has been adapted to explain the nonlinearity of the SnO2 -based varistor.

In this paper, two different processing routes were adopted for the preparation of lead-free (Na 0.52 K 0.44 Li 0.04 )Nb 0.87 Sb 0.08 Ta 0.05 O 3 ceramics and favorable results were obtained. The samples were characterized by X-ray techniques and scanning electron microscopy. Piezoelectric and dielectric data were presented. All the (Na 0.52 K 0.44 Li 0.04 )Nb 0.87 Sb 0.08 Ta 0.05 O 3 samples possessed pure perovskite phase, and not any secondary phase could be certified. Excellent piezoelectric properties of d 33 = 376pC/N, k p = 44.1% and tan δ = 2.4% were obtained for the composition compounded with (Na 0.52 K 0.44 Li 0.04 )NbO 3 and (Na 0.52 K 0.44 Li 0.04 )Nb 0.74 Sb 0.16 Ta 0.1 O 3 in the molar ratio 1:1. The remarkably strong piezoelectricity is probably due to the improved compositional homogeneity and enhanced densification achieved by the two-stage preparation method. The work will lead to further improvements in the properties of KNN-based piezoelectric materials.

Lead-free (K 0.5 Na 0.5 ) 0.94 Li 0.06 (W 2/3 Bi 1/3 ) x Nb 1 − x O 3 ceramics were prepared by conventional solid-state sintering. The samples were characterized by X-ray techniques and scanning electron microscopy. The piezoelectric and dielectric properties were also investigated by varying the doping amount of W 2/3 Bi 1/3 . All the samples have tetragonal perovskite structure, and no secondary phases are formed in the range detected. Proper amount of W 2/3 Bi 1/3 improves the piezoelectric activity, playing a soft doping role. The piezoelectric constant d 33 and planar mode electromechanical coupling coefficient k p show maximum values of 282 pC/N and 45% in the ceramics with x = 0.008. The results show that the introduction of constructed quinquevalent (W 2/3 Bi 1/3 ) 5 + cation is very effective in improving the electrical properties of KNN-based ceramics.

Y2O3 thin film waveguides were prepared by RF magnetron sputtering. The effects of post-deposition annealing on the structure and optical properties have been investigated. The structural evolution of Y2O3 films with annealing temperature was investigated by X-ray diffraction (XRD). Spectroscopic ellipsometry was employed to determine the optical properties of Y2O3 films annealed at various temperatures. It was found that with increasing annealing temperature, the refractive index (n) of Y2O3 films increases. The optical band gap of Y2O3 films shifts to higher energy after higher temperature annealing, which is likely due to the reduction of defects and the change of crystalline structure in Y2O3 films.