Lianwei Shan

Enhanced photocatalytic properties of molybdenum-doped BiVO4 prepared by sol–gel method

Bismuth vanadate (BiVO4) has been investigated intensively and extensively due to its potential applications in the photocatalytic treatment of organic-containing wastewater. In this study, Mo-BiVO4 samples were synthesized by a facile sol–gel process. These samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and ultraviolet–visible (UV–Vis) diffuse reflectance spectroscopy. It is found that the phase structure of Mo-BiVO4 photocatalyst is monoclinic scheelite. The photocatalytic activities of the obtained BiVO4 samples were investigated by means of the decolorization efficiency of methyl orange (MO). The BiVO4 and Mo-BiVO4 photocatalysts show the response on the visible light. The doped BiVO4 photocatalysts show higher decolorization efficiency than that of bare BiVO4.

Fabrication and characteristics of strontium barium niobate/barium strontium titanate ceramics by powder–sol method

Abstract Barium strontium titanate (Ba 1- x Sr x TiO 3 , BST) and strontium barium niobate (Sr x Ba 1- x Nb 2 O 6 , SBN) are important ferroelectric materials with excellent pyroelectric, dielectric properties and faster response time of infrared radiation. SBN/BST composite ceramics with different mole ratios of Nb and Ti were fabricated using a powder-sol (P-S) method with Nb 2 O 5 fine powders suspended in the barium strontium titanate (BST in short) sol solution. The X-ray diffraction results indicate that three intermediate phases, i.e. TiO 2 , BaNb 2 O 6 and SrNb 2 O 6 , are developed during the formation of SBN-BST. Powders obtained from dried gels are calcined at 800 ? for 3 h. The Ti 2p spectra of only one spin-orbit doublet are observed, which indicates one 4+ chemical state in the composite ceramics. The binding energies of Nb element depend strongly on composition.

Study on preparation and magnetic properties of Sr1-xGdxFe12-xCuxO19 (0.00 ≤ x ≤ 0.20) strontium ferrite prepared by solid phase method

ABSTRACT M-type strontium ferrites (Sr1-xGdxFe12-xCuxO19, x = 0.00, 0.05, 0.10, 0.15 and 0.20) doped with equivalent ions were synthesized via the solid phase method. The crystallographic structure, morphology and magnetic properties of samples were investigated using x-ray diffractometry (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM), respectively. The XRD results show that the pure M-type phase is successfully obtained when the Gd–Cu substitution amount x below 0.20. When the doping content is low, the typical hexagonal block structure appears in the magnet. When x is 0.05, the saturation magnetization (Ms), remanent magnetism (Mr) and coercivity (Hc) reach the maximum values of 51.25 emu/g, 565.50 Oe and 27.67 emu/g, respectively.

Luminescence performance of yellow phosphor Sr x Ba 1− x TiO 3 : Eu 3+ , Gd 3+ for blue chip

The SrxBa1-xTiO3: Eu3+, Gd3+ phosphors are synthesized by high temperature solid-phase method. Multiple techniques including X-ray diffraction (XRD), and scanning electron microscopy (SEM) are used to examine the surface morphology and structural properties of SrxBa1-xTiO3: Eu3+, Gd3+ phosphors. The optical properties are presented and discussed in terms of photoluminescence (PL) and photoluminescence excitation (PLE) spectra. The as-obtained SrxBa1-xTiO3: Eu3+, Gd3+ phosphors show higher PL emission intensity (at 591, 611 nm). The peaks at 591 and 611 nm are attributed to Eu3+ 5D0-7F1, 5D0-7F2. Gd3+ has a strong sensitization on Eu3+. A certain amount of Sr2+ and Ba2+ is contributed to the intensity of light emission. After being irradiated with blue light, the phosphor samples emit yellow light. This suggests its potential applications in many fields.

Microstructure and Microwave Properties for Barium Magnesium Niobate

Relaxor-type ferroelectric perovskites (Ba,La)(Mg,Nb)O3(BLMN) ceramics have been synthesized from oxides by sintering in airs using a conventional mixed oxide process. From the XRD patterns, it is found that the amount of the perovskite phase increases with the increasing amount of La2O3. Furthermore, by the X-ray photoelectron spectroscopy (XPS) analyzation, it is discovered that the amount of Nb4+ is increased as La2O3 dopants increase from 0 to 0.04. Microwave properties of ceramics was also discusses in relation to the microstructure and density.

The magnetic properties of permanent strontium ferrite doped with rare-earth by chemical co-precipitation method

ABSTRACT The Sr1-xSmxFe12-xCuxO19 (0 ≤ x ≤ 0.2) materials were prepared by chemical co-precipitation technique. The products were characterized by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), scanning electric microscopy (SEM) and vibrating sample magnetometer (VSM). The results of XRD showed that the pure M-type hexaferrites are obtained. The Sm3+ and Cu2+ ions were completely doped into strontium ferrite phase. With the increasing of Sm-Cu content, the grain size gradually increases. The FTIR spectra of annealed samples of Sr1-xSmxFe12-xCuxO19 showed that strontium hexaferrite particles have been successfully synthesized and M-type SrFe12O19 intrinsic crystal structure has not been destroyed. A filed emission scanning electric microscopy was employed to explore the micrographs of the magnets. The hexaferrite magnets have formed hexagonal-shaped crystals. The magnetic properties were tested by VSM. In the single M-type phase region, the variation of magnetic properties with Sm-Cu substitution amount is well explained based on the occupancy effect of Sm3+, Cu2+ in magnetoplumbite structure. The results indicate that the Br increases and then decrease when rare-earth content (x) continutes to increase. With the dosages of Sm-Cu from 0 to 0.20, the Hc at x = 0.15 reach the maximum value of 6862.62 Oe.

Dielectric properties for strontium barium titanate thin films with different thickness

ABSTRACT In this work, Sr0.5Ba0.5TiO3 (SBT) thin films with different thickness were prepared on a Pt/SiO2/Si substrate by sol-gel process. The microstructures of SBT thin films were examined by X-ray diffraction(XRD) and trans- mission electron microscopy (TEM). Morphologies of samples were characterized by field-emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). The influences of thickness on the microstructure and dielectric properties of SBT thin films were also studied. It is found that tetragonal perovskite crystal grains existed in SBT thin films. The results indicated that the optimum thickness is 450 nm for SBT thin films.

Dielectric properties of powder-sol-derived strontium barium niobate/strontium barium titanate composite ceramics

ABSTRACT In this paper, strontium barium niobate/strontium barium titanate [SrxBa1-xNb2O6/SrxBa1-xTiO3] composite ceramics with different Sr2+/Ba2+ ratio were fabricated using a Powder-Sol (P-S) method. The formation process of SBN/SBT was studied by TG-DTA. It is found that the tetragonal tungsten bronze (TTB) phase and perovskite phase were co-present in the composite ceramics, and the Sr2+/Ba2+ ratio has an influence on the proportion between SBN and SBT. SEM results show that samples are homogeneous and fine-grained. The dielectric properties of composite ceramics were studied by impedance analyzer, and indicates that the dielectric constant and dielectric loss could be well regulated by Sr2+/Ba2+ ratio.

PREPARATION OF ZnO:Tm, Gd AND ITS FLUORESCENCE PROPERTIES

ZnO:Tm, Gd materials with high quality blue light emissions were successfully prepared using the chemical co-precipitation method. The surface morphology, composition, crystal structure and fluorescence properties were investigated using the thermogravimetric analysis/differential thermal analysis (TG/DTA), scanning electronic microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL). The results showed that the lowest sintering temperature was 580°C; the optimal sintering temperature was 900°C; ZnO:Tm3+, Gd3+ had two emission peaks: 1D2→3H4 and 1G4→3H6; the optimal heat preservation time was 3 h; the proportion of matrix and doping elements was 100:2; and the optimal proportion of Tm and Gd was 3:2.