Advanced Materials Research Vols. 399-401

Abstract: Rare-earth doped glass-ceramics were prepared by heat-treating the precursor germanate glasses. The crystalline phases of the glass-ceramics were assigned to be NaAlGeO₄ (NAG) and Mg₂GeO₄ (MG), and the primary particle sizes were derived to be ~31 and ~32nm, respectively. The secondary particle size of crystal grains was estimated to be ~30µm, and the large grain size is owing to the particles aggregation. Under 254 and 365nm radiation, Sm³⁺-doped glass-ceramics exhibit orange and reddish-orange fluorescences, and Eu-doped glass-ceramics present red and purplish-red lights, respectively. The investigation results of excitation spectra indicate that the Sm³⁺- and Eu-doped NAG-MG glass-ceramics can be excited efficiently by commercial UV and blue laser diodes, as well as blue and bluish-green LEDs.

Abstract: The positron annihilation techniques and Mössbauer spectroscopy have been used to study the signals of 3d electrons and the hyperfine interactions in ordered and disorder Fe₅₀Al₅₀ alloys. The results show that the signals of 3d electrons of ordered Fe₅₀Al₅₀ alloy is very low. Mössbauer spectrum of ordered Fe₅₀Al₅₀ alloy shows a singlet, this alloy is paramagnetic. However, Mössbauer spectrum of Fe₅₀Al₅₀ powder being ball-milled for 70 h shows a discrete sextet, indicating a decrease in the long-range order within the Fe₅₀Al₅₀ powder being ball-milled for a long time.

Abstract: The effect of different doses of gamma radiation (0.5 Gy, 1.5 Gy, 5.0 Gy, 10.0 Gy and 50 kGy) on the maximum load and deflection of the Single Die Quad Flat No Lead (SDQFN) semiconductor package has been investigated. The three-point technique was carried out to obtain the maximum load and deflection of the package. The results of irradiated SDQFN show the decreasing in their maximum load and deflection with the increasing of gamma irradiation dose. The higher gamma irradiation dose produced the more significant change in the load-deflection behaviour of the irradiated SDQFN. The package becomes prone to failure when exposed to the radiation environment.

Abstract: The title compound, [Na(μ_1,1,2,3-oxalato)(di-μ_{belongs to triclinic, space group P-1 with a = 5.6982 (11), b = 6.5040 (12), c = 6.6647 (13) Å, α = 75.040 (2), β = 84.990 (3), γ = 70.072 (3), V = 224.34 (7) ų, C2H3NaO5, Mr = 130.03, Z = 2, Dc = 1.925 g/cm³, μ = 0.270 mm^–1 and F(000) = 132. Each sodium ions is located on crystallographic inversion symmetry centre and surrounded by six oxygen donors from three oxalate ligands and two di-μ1,1-waters in a distorted octahedron geometry. Two planar 4-member cyclβes crystallographic inversion are found in alternate repeated Na2O2 subunit, which is further extended to two dimensional supermolecular fragment via μ1,1,2,3-oxalato-bridged. The crystal structure is aggregated to a 3D network through O-H…O hydrogen bonding involving the water molecules and oxalate oxygen atoms.}

Abstract: Rare-earth luminescence materials in lighting the tube and the field emission fields has been widely applied.In the leds, special security lights and energy-saving lighting are in the areas of infinite good prospect, this paper the research progress of preparation and a concrete discussion . The ultrasonic method for Y₂O₃:Eu³⁺ nanocrystal, annealing conditions on the Y₂O₃:Eu³⁺ nanocrystal particles size, crystal condition and the influence of the luminescence properties.The properties of the Y₂O₃:Eu³⁺ complexes were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Reaction conditions, such as ultrasonic power and the temperature were found to have close relation with the morphologies of final products.

Abstract: BaTiO₃ (BTO) thin films were grown on (100) SrTiO₃ (STO) single crystal substrates using the RF-magnetron sputtering technique (RFMS) in both pure argon and mixed Ar/O₂ (20% O₂) atmosphere. A La_0.5Sr_0.5CoO₃ (LSCO) layer was deposited as the bottom electrode by a 90° off-axis single-target RFMS. θ-2θ X-ray diffraction measurements showed that BTO thin films grown in both cases had a highly preferred c-axis orientation (001). From hysteresis measurements, it was confirmed that both films are ferroelectric. The ferroelectric polarizations 2Pr were 6.6 μC/cm² and 27.1 μC/cm², for the BTO films grown in pure argon and in mixed Ar/O₂ atmosphere, respectively.

Abstract: Spectroscopic properties and energy transfer (ET) in Er³⁺/Eu³⁺-doped Ga2O3-GeO2 glass have been investigated. Effects of alkali metal and alkaline earth metals ions on thermal stability of Er³⁺-doped gallate-germanium glass have been investigated. Simultaneously influences of Eu³⁺ codoping on the optical properties of Er³⁺-doped Ga₂O₃-GeO₂-Na₂O (GN) glass have been investigated and the possible ET mechanisms involved have also been discussed. Significant enhancement of the 1.53 µm emission intensity and decrease of upconversion (UC) fluorescence with increasing Eu3+ concentration have been observed. The results indicate that the incorporation of Eu³⁺ into Er³⁺-doped GN glass can effectively improve 1.53-μm and lower UC luminescence, which makes GN glass more attractive for their use in C-band optical fiber amplifiers.

Abstract: The III-nitride compounds epitaxially grown on Si substrate have attracted more and more attentions and some progress have been achieved. Many methods have been tried to tackle the issue which caused by the large lattice mismatch and thermal expansion coefficient mismatches between silicon substrate and the III-nitride compounds. This paper presents buffer layer technology, selective area and lateral epitaxial over growth technology, and presents the researches about the III-nitride devices. Semi polar and non-polar GaN films grown on Si (such as Si(110), Si(112), Si(001) et al.) also have been instructed. At the end of this paper, the development trend of epitaxial technology has been discussed.

Abstract: A new unsymmetrical photochromic diarylethene 1-(2-methylbenzothiophene-3-yl)-2-(2-nbutyl-5-(2,2′-dicyanovinyl)thiophene-3-yl)perfluoroncyclopen-tene (1a), was synthesized and its optoelectronic properties, such as photochromism in solution as well as in poly-methylmethacrylate (PMMA) amorphous films, and the fluorescence spectra of diarylethene 1a was investigated. The photochromic reaction kinetics indicated that the cyclization process of 1a belongs to the zeroth order reaction and the cycloreversion process belongs to the first order reaction. The diarylethene can be potentially used as holographic optical recording medium.

Abstract: By using microbial reduction combining natural oxidation method, magnetic Fe₃O₄ nanoparticles have been synthesized. Sulfate-reducing bacterium(SRB) was used to reduce ferric sulfate to produce ferric sulfide, then ferric sulfide was oxidized to iron protoxide and ferroferric oxide in the end under natural air oxidation condition. The size and morphology of the product and SRB was examined by scanning electron microscopy(SEM), the microstructure were investigated by X-ray diffraction(XRD) and energy dispersive spectroscopy(EDS). There are only two components(xFeO and yFe₃O₄)which is testified by XRD and EDS. The constituents of product were analysed by using energy dispersive spectroscopy(EDS). In result, x,y actual numerical value which is respectively mole fraction of FeO and Fe₃O₄ in the product is figured out 0.678 and 0.322.