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.

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.

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.

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.

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.

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.

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

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.

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.

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).

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.

Effect of Yb_2O_3 Additive on Transformation Behavior of Anatase for TiO_2/(O′+β′)-Sialon Multi phase Ceramics

TiO2/（O＇ ＋ β＇）-Sialon multiphase ceramics were prepared with nano TiO2 （anatase） powder and （O＇ ＋ β＇）-Sialon powder as raw materials. Effect of Yb2O3 additive on transformation behavior of anatase for TiO2/（O＇ ＋ β＇）-Sialon multi phase ceramic was investigated and its influence mechanism was discussed. XRD was employed for the analysis of phase composition and lattice parameters. The results show that even though Yb2O3 has no obvious influence on starting temperature of phase transformation, it significantly accelerates the transformation process, which displays a weakened effect with more Yb2O3 addition. There exist two forms of the added Yb2O3 ： some enters TiO2 lattice and the other deposits on the surface of TiO2. The function of Yb2O3 on phase transformation of anatase can be attributed to the coaction of active and negative influence mechanisms as follows： some Yb^n＋ enter TiO2 lattice and replace Ti^4＋ , as well as the redox reaction between Yb^3＋ and TiO2, which promote the transformation, whereas other Yb2O3 deposits on the surface of TiO2, and Ti- O-Yb bond is formed by the coaction of Yb^3＋ and TiO2, which inhibit the process.

Effect of La_2O_3-Dopant on Microstructure and Microwave Dielectric Properties of CaO-MgO-Nb_2O_5-TiO_2 System Ceramics

La_2O_3-doped CaO-MgO-Nb_2O_5-TiO_2 system ceramics were prepared by solid-state ceramic technique. The microstructure and microwave dielectric properties of CaO-MgO-Nb_2O_5-TiO_2-La_2O_3 ceramics can be adjusted by varying the amount of La^(3+) ions. The results show that the replacement of Ca^(2+) by La^(3+) at A-site of the ceramics can increase the quality factor Q·f value as well as the temperature coefficient of resonant frequency τ_f and decrease the dielectric constant ε_r. With increase of La^(3+) contents, the dielectric constant decreases from 57 to 35 and Q·f value increases from 33400 GHz to 35000 GHz (at 7.6 GHz). Meanwhile, the temperature coefficient of resonant frequency is improved towards near zero. The dielectric properties of these compounds are related to octahedra tilting due to deficient vacancies at A-site.

Impedance Characteristics of MgO-ZrO_2 Ceramics Doped with CeO_2

The ultrafine CexMg0.06Zr1-xO1.94 （ x = 0 16% ） powders were synthesized by a chemical co-precipitated method. The pressed compacts were sintered in air at 1300, 1400, 1500, 1600℃ for 3 h, respectively. The phase of the ceramics was characterized by the X-ray diffraction （XRD） method. The conductivity of the ceramics was measured by the AC complex impedance technique at 700- 1200 ℃. The ratio of the cubic phase in the ceramics improves with increasing CeO2 content, leading to a enlargement of the oxygen ionic migration channel. The contact resistance between conductive phase particles decreases with increasing CeO2 content, leading to a lower migration hindrance of the oxygen ionic. Consequently, the ionic conductivity of the ceramics improves with increas- ing CeO2 content. Additionally, an analysis for this phenomenon was also presented.

Effect of La^(3+), Sr^(2+) on Microwave Dielectric Properties of CaO-MgO-Nb_2O_5^-TiO_2 System Ceramics

The effect of La^3 ＋ , Sr^2＋ on the microstructure and microwave properties of CaO-MgO-Nb2O5-TiO2 system ceramics was investigated. The result shows that a single complex perovskite structure formed within investigated composition range in La^3＋ , Sr2-doped CaO-MgO-Nb2O5-TiO2 system ceramics. With increasing of La^3＋ , Sr^2＋ content, the structure of La^3＋ , Sr2-doped CaO-MgO-Nb2O5-TiO2 system ceramic respectively maintain orthorhombic type.

Heat Treatment of Nd_(1+x)Ba_(2-x)Cu_3O_(7-δ) Superconductors

Two kinds of Nd 1+ x Ba 2- x Cu 3O 7- δ , the sintered samples and zone melted samples, were treated in pure Ar at 950 ℃. The substitution of Nd ions for Ba ions in the Nd 1+ x Ba 2- x Cu 3O 7- δ before and after the heat treatment was investigated by XRD. In order to know the effects of heat treatment, the T c and J c of samples with and without the heat treatment in Ar were comparatively studied. The results show that the substitution of Nd for Ba decreases, whereas T c and J c increase after the treatment. The Nd 1+ x Ba 2- x Cu 3O 7- δ samples were oxygenated in pure oxygen at 300 ℃ . Based on the XRD spectra it was found that the samples with x <0.4 can transform from tetragonal phase into orthorhombic phase after the oxygenation, whereas in the sample with x >0.4 no phase transition occurs even after a long time oxygenation.

Influences of deposition parameters on the microstructure and properties of nanostructural TiN films synthesized by filtered cathodic arc plasma

Titanium nitride （TIN） films with nanostructure were prepared at ambient temperature on a （111） silicon substrate by the filtered cathodic arc plasma （FCAP） technology with an in-plane ＂S＂ filter. The effects of deposition parameters on the grain size, texture and nano-hardness of the films were systematically investigated. The grain size was obtained through calculation using the Scherrer formula and observed by TEM. The results of X-ray diffraction and electron diffraction indicated that increasing either negative substrate bias or argon flow promoted the formation of （111） preferred orientation. High argon flow leads to biaxial texture. The micro-hardness of the TIN films as a function of grain size showed a behavior according to the Hall-Petch relation under high argon flow.

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.