Synthesis of Long Afterglow Photoluminescent Materials Sr_2MgSi_2O_7∶Eu^(2+), Dy^(3+) by Sol-Gel Method

Long afterglow photoluminescent materials Sr2MgSi2O7 doped with Eu2+, Dy3+ were prepared by sol-gel method. The synthesized samples were characterized by X-ray diffraction. The excitation spectrum, emission spectrum and long decay curve were measured and analyzed. XRD pattern indicates that phosphor is with Sr2MgSi2O7 crystal structure. The wide range of excitation wavelength indicates that luminescent material can be excited by light from ultraviolet ray to visible light. The main peak of emission spectrum is located at 466 nm. Sample excited by visible light can emit bright blue light, and the afterglow time lasts more than 8 h.

LiMn_2O_4 thin films derived by rapid thermal annealing and their performance as cathode materials for Li ion battery

The LiMn2O4 thin film as a cathode material was prepared through solution deposition followed by rapid thermal annealing （RTA）. The phase identification and the study of surface morphology were carried out by X-my diffraction and scanning electron microscopy. Electrochemical properties were examined by cyclic voltammetry, galvanostatic charge-discharge experiments, and electrochemical impedance spectroscopy. The results show that the film prepared by this method is homogeneous, dense, and crack-free. The thin film has a capacity of 38 μtAh/（cm^2·μm） with the capacity loss of 0.037% per cycle after being cycled for 100 times. The average diffusion coefficient for lithium ions in the RTA-derived LiMn2O4 thin film is 1×10 ^-10 cm^2·s^-1.

Structure and Electrorheological Performance of Nanosized Y_2O_3-Doped TiO_2 Particle Materials

The nanosized particle materials of doped-TiO_2 with Y_2O_3 were prepared by means of sol-gel technique for use in electrorheological (ER) fluids, and their crystal structures were measured by X-ray diffraction (XRD) analysis. To compare with the pure TiO_2, a distinct enhancement in the shear stress under dc electric field was found by using such materials. This can be explained by the increase of the dielectric loss and dielectric constant at low frequency. The effects of the crystal structure of the particles on the dielectric property and ER performance of materials were investigated.

Effects of Rare-Earth La_2O_3 Addition on Microstructures and Electrical Properties of SrTiO_3 Varistor-Capacitor Dual Functional Ceramics

The effects of rare-earth La_2O_3 addition on microstructures and electrical properties of SrTiO_3 ceramics were investigated. Semiconductor SrTiO_3-based voltage-sensing and dielectric dual functional ceramics was prepared by a single step sintering technology in this study, and the effects of the content of La_2O_3 on characteristics of the product were discussed in terms of microstructures and electrical properties of materials. The results show that SrTiO_3-based ceramics doped with La_2O_3 exhibits more homogeneous grain distribution, greater grain size, and excellent voltage sensing and dielectric characteristics than those without La_2O_3 doping. The samples doped with 1 1% La_2O_3 were sintered at 1420 ℃ in N_2+C weak reducing atmosphere. The average grain size of the samples doped with La_2O_3 is 40 μm, the breakdown voltage of 19.7 V·mm^(-1), the nonlinear exponent of 7.2, and dielectric constant of 22500. The results reveal that final products are suitable to use in low operating voltage.

Effect of La_2O_3 on Microstructure and Transmittance of Transparent Alumina Ceramics

Optically transparent alumina ceramics were fabricated by conventional process and sintered without pressure in H2 atmosphere. The results indicate that relative densities of alumina specimens increase to theoretical densities （T. D. ） with increasing content of La2O3. With increasing holding time during sintering, much less pores and larger grains were found in the sintered alumina samples. Higher transmittance was achieved in alumina codoped with MgO and La2O3 as compared with that doped with MgO only. The total-transmittance of alumina sample is up to 86% at twavelength range of 300 - 800 nm.

Upconversion Emission in Er^(3+) Doped Novel Bismuthate Glass

Novel Er3+-doped bismuth lead strontiam glass was fabricated and characterized, and the absorption spectrum and upconversion spectrum of the glass were studied. The Judd-Ofelt intensity parameters Ωt (t=2, 4, 6) were found to be Ω2=3.27×10-20 cm2, Ω4=1.15×10-20 cm2, and Ω6=0.38×10-20 cm2. The oscillator strength, the spontaneous transition probabilities, the fluorescence branching ratios, and excited state lifetimes were also measured and calculated. The upconversion emission intensity varies with the power of infrared excitation intensity. A plot of log Iup vs log IIR yields a straight line with slope 1.86, 1.88 and 1.85, corresponding to 525, 546, and 657 nm emission bands, respectively, which indicates that a two-photon process for the red and green emission.

Influence of Composition of Sm_2O_3-Containing Rare Earth Glass on Its Absorption Spectrum

Borosilicate glass with high rare earth content was fabricated by traditional method. The influence of glass compositions and rare earth content on absorption spectra was examined and discussed. With increasing Sm2O3 content, the intensity of characteristic absorption peak is increased and the absorption peak is broadened. With increasing of the ratios of SiO2/B2O3 and Al2O3/SiO2, the broadening degree of absorption peak is increased. The experimental results provide basis for making special optical glasses which have the characteristics of high absorption for special wavelength laser and high transparence for visible light.

Complex permittivity, permeability, and microwave absorption of barium ferrite by citrate sol-gel process

BaFe12O19 hexaferrites were prepared by citrate sol-gel process. The formation temperature was much lower than that of the conventional ceramic method. The complex dielectric constant and complex permeability of hexaferrite-paraffin wax composites had been measured by the transmission/reflection coaxial line method in the range from 200 MHz to 6 GHz. The measurement results showed that both the complex dielectric constant and dielectric loss exhibited no significant variation with the measuring frequency increase. It also showed that the real part of permeability decreased as the frequency increasing for all samples, the resonance phenomena due to domain wall resonance was observed in ?' spectra, the calcining temperature strongly affects the microwave properties of BaFe12O19 ferrites, the higher the calcining temperature, the lower the resonance frequency.

Spectroscopic Properties and Judd-Ofelt Theory Analysis of Er^(3+)-Doped Heavy Metal Oxyfluoride Silicate Glass

Er^(3+)-doped heavy metal oxyfluoride silicate glass was fabricated and characterized, and the absorption spectrum and fluorescence spectrum of the glass were studied. The Judd-Ofelt intensity parameters Ω_t (t =2, 4, 6), spontaneous transition probability, fluorescence branching ratio and radiative lifetime of each energy levels for Er^(3+) were calculated by Judd-Ofelt theory, and stimulated emission cross-section of (()~4I_(13/2))→(()~4I_(15/2)) transition was calculated by McCumber theory. The results show that fluorescence full width at half maximum and stimulated emission cross-section of Er^(3+)-doped heavy metal oxyfluoride silicate glass are broad and large, respectively. Compared with other host glasses, the gain bandwidth property of Er^(3+)-doped heavy metal oxyfluoride silicate glass is close to those of tellurite and bismuth glasses, and has advantage over those of silicate, phosphate and germante glasses.

Degradation of crystal violet using nanometer TiO_2 under the synergistic action of H_2O_2 and ultrasonic wave

TiO_2 nanoparticles with different phases are prepared by hydrolysis oftitanium tetrabutoxide in the presence of HC1. The composition and microstructure of the resultingsamples are studied by XRD and TEM. These results show that the range of particle size of TiO_2 isfrom 20 to 30 nm. The mechanism of TiO_2 photocatalysis reaction has been discussed extensively.Photocatalytic activities of nanometer TiO_2 are also evaluated by degradation of the crystal violetsolution. Experimental results indicate that the synergistic action of H_2O_2 and ultrasonic wavegreatly enhances photo-catalytic reaction of TiO_2.

Optics and Spectral Investigation in Dy^(3+)-Doped Borate Glasses

Dy^3＋-doped borate glasses （LBLB） with high effective visible fluorescence emission were synthesized. The absorption spectrum and fluorescence spectrum of this glass were measured and analyzed. By using J-O theory, the oscillator strengths for some absorption transitions were calculated according to the absorption spectra. The intensity parameters Ω1 （t = 2, 4, 6） of Dy^3＋ were determined by using a least-squares fitting approach, and the values are 4.04 × 10^-20, 1.30 × 10^-20 and 1.82 × 10^-20 cm, respectively. The root-mean-square deviation δrma was calculated. Under UV light excitation, Dy^3＋-doped borate glasses （LBLB） emit intense yellowish white lights. The excitation spectrum indicates that argon laser is the effective excitation source in Dy^3＋-doped LBLB glasses

Effects of Dysprosium Oxide Doping on Microstructure and Properties of Barium Titanate Ceramic

Different amounts of dysprosium oxide were incorporated into barium titanate powders synthesized by hydrothermal method. Relations of substitution behaviors and lattice parameters with solid-solubility were studied. Furthermore, the influences of dysprosium oxide doping fraction on grain size and dielectric properties of barium titanate ceramic, including dielectric constant and breakdown electric field strength , were investigated via scanning electron microscope, X-ray diffraction and electric property tester. The results show that dysprosium oxide can restrain abnormal grain growth during sintering and that fine-grained and high density of barium titanate ceramic can result in excellent dielectric properties. As mass fraction of dysprosium oxide is 0.6%, the lattice parameters of grain increase to the maximum because of the lowest vacancy concentration. The electric property parameters are cited as following： dielectric constant （25 ℃ ） reaches 4100, the change in relative dielectric constant with temperature is - 10% to 10% within the range of - 15 - 100 ℃, breakdown electric field strength （alternating current） achieves 3.2 kV·mm^-1, which can be used in manufacturing high voltage ceramic capacitors

Synthesis and characterization of SrCe_(0.95)Y_(0.05)O_(3-δ) nano powders by low temperature combustion

Nanosized SrCe0.95Y0.05O3-δ powders with homogeneous composition were synthesized by the low temperature combustion process based on the Pechini method. A polymeric precursor sol was formed by using citric acid and ethylene glycol as the chelating agents of metal ions. The perovskite-type SrCe0.95Y0.05O3-δpowders with uniform shape and smaller than 25 nm in size were obtained through the combustion of the polymeric precursor sol at the existence of nitric acid and ammonium hydroxide. It was found that modulating the quantifies of nitric acid and ammonium hydroxide could control the particle size, and the quantities of residue carbonate ions were also affected by the quantifies of citric acid and ethylene glycol.

Spectroscopic Characterization of Nd-Doped Gadolinium Vanadate Crystals

The Nd 3+ doped gadolinium vanadate Nd∶GdVO 4 is a new type of crystal with laser properties superior to Nd∶YVO 4. Experiment results show that the former has larger absorption cross section (3.261×10 -19 cm 2) and larger emission cross section (9 283×10 -20 cm 2). The heat conductivity of Nd∶GdVO 4 is similar to that of Nd∶YAG, therefore it is a promising crystal for LD pumped laser. It is used to gain compact, high effect and all solid state lasers. The absorption spectra and fluorescence spectra were reported and the relationship between spectra and crystal structure was analyzed. Characteristics of energy levels of Nd 3+ in the Nd∶GdVO 4 crystal were discussed. The possibility of achieving laser oscillation at 0.91 μm was discussed.

Particular properties of Ti_2O and TiN_x nanoparticles prepared by thermal decomposition

Particular properties of Ti2O and TiNx prepared by thermal decomposition were introduced. A precursor prepared by titanium powder reacting with oxalate acid was thermally decomposed in nitrogen atmosphere at 840℃ for 15 min, and relatively pure Ti2O was then obtained. Conductive TiNx was also prepared after altering reaction conditions. Samples were characterized by resistivity, X-ray powder diffraction, transmission electron microscope, Ultraviolet-Visible diffuse reflection, and electromagnetic shielding efficiency. The results indicate that both Ti2O and TiNx have good conductivity. Moreover, Ti2O shows a better solar photocatalytic activity and TiNx does well in the electromagnetic shield.

Piezoelectric and dielectric properties of Cr-doped PSN-PZN-PZT qua-ternary piezoelectric ceramics

PSN-PZN-PZT + x wt. %Cr2O3, X = 0.0-0-9, were prepared by conventional mixed oxide techniques at sintering temperatures of 1220 degrees C-1300 degrees C for 2 h. The effect of sintering temperature on the microstructure and the piezoelectric properties was investigated by XRD, SEM, and other conventional measurement. The result indicated that with temperature increasing, the valence of Cr ion from Cr5+ or Cr6+ changes into C3+, and the piezoelectric properties turn hard. With increasing Cr2O3 content, the amount of rhombohedral phases increases and the morphotropic boundary phase is correspondingly shifts to rhombohedral phase. A uniform microstructure and excellent comprehensive properties were obtained at 1240 degrees C as the amount of Cr2O3 is 0.5 wt.%.

A New Combustion Process for Nanosized BaCe_(0.95)Y_(0.05)O_(3-δ) Powders

Nanosized BaCe_(0.95)Y_(0.05)O_(3-δ) powders with the homogeneous composition were synthesized by a new combustion process based on the Pechini method. A polymeric precursor sol was formed by use of citric acid and ethylene glycol as the chelating agents of metal ions. The perovskite-type BaCe_(0.95)Y_(0.05)O_(3-δ) powders with uniform shape and smaller than 40 nm in sized were obtained through the combustion of the polymeric precursor sol at the existence of nitric acid and ammonium hydroxide. It was found the particle size could be controlled by modulating the quantities of nitric acid and ammonium hydroxide, the quantities of the residue, carbonate ions were also affected by the quantities of the citric acid and ethylene glycol.

Study on Preparation and Electrical Properties of Ba_(1.03)Ce_(0.8)Eu_(0.2)O_(3-α) Solid Electrolyte

Ba_(1.03)Ce_(0.8)Eu_(0.2)O_(3-α) solid electrolyte with nonstoichiometric composition was prepared by high temperature solid-state reaction. Phase composition, surface and fracture morphologies of the specimen were characterized by using XRD and SEM, respectively. Ionic conduction was researched by gas concentration cell, the performance of hydrogen-air fuel cell was measured in the temperature range of 600～1000 ℃, and compared them with those of BaCe_(0.8)Eu_(0.2)O_(3-α) and Ba_(0.98)Ce_(0.8)Eu_(0.2)O_(3-α). The results indicate that Ba_(1.03)Ce_(0.8)Eu_(0.2)O_(3-α) is a single-phase perovskite-type orthorhombic system. It is a pure proton conductor in the temperature range of 600～1000 ℃ in hydrogen atmosphere, and its proton conduction is superior to that of BaCe_(0.8)Eu_(0.2)O_(3-α) and Ba_(0.98)Ce_(0.8)Eu_(0.2)O_(3-α). It is a mixed conductor of oxide ion and electron hole in oxygen atmosphere. At 1000 ℃, the performance of the fuel cell in which Ba_(1.03)Ce_(0.8)Eu_(0.2)O_(3-α) as electrolyte is higher than that of BaCe_(0.8)Eu_(0.2)O_(3-α) or Ba_(0.98)Ce_(0.8)Eu_(0.2)O_(3-α).

Zn-catalytic growth and photoluminescence properties of branched MgO nanostructures

Mass production of uniform MgO nanostructures has been achieved by a thermal evaporation method. X-ray diffraction （XRD） analyses show the product is composed of pure single-crystalline MgO. Scanning electron microscopy （SEM） and transmission elecwon microscopy （TEM） characterizations show that the MgO branched nanostructures consist of many sfim nanowires growing from the thick MgO rods. The as-synthesized nanowires have a length of several tens of microns and a diameter of several tens of nanometers. The preferred growth direction of the nanowires is [001]. Many nanowires are found to have a dendritic structure and temperature grade is thought to be the main cause of the growth of this structure. Zn nanoparticles scattered on the surface of the MgO rods are thought to be the catalyst of the VLS （vapor-liquid-solid） growth of the MgO nanowires. Room-temperature photoluminescence measurements show that the synthesized MgO nanostructures have a strong emission band at 401 nm and a weak emission band at 502 nm.

A comparative study of the properties of TiN films deposited by MAIP and FCAP

In this study two types of TIN films were prepared, one using the filtered cathodic arc plasma （FCAP） technique with an in-plane ＂S＂ triter, and the other using the multi-arc ion-plating （MAIP）, and both deposited under the same parameters. Comparisons of the texture, hardness, roughness, tribological and electrochemical corrosion behaviors of the two types of TiN films were given. The TiN films obtained by the FCAP technology were found to be highly uniform, smooth and macroparticle-free. The TiN films deposited by FCAP had a （111） preferred orientation, while there was no texture in the films deposited by MAIP. Under low load the two kinds of TiN coatings had very different wear mechanisms; the films of FCAP had a lower wear rate and friction coefficient compared with the TiN films deposited by the MAIP technique. The dense and hole-free structure of TiN films of FCAP could effectively avoid the avalanche of TiN films from the substrate during corrosion tests.