Structural,Optical, and Magnetic Properties of Nd‐Doped GaN Powders

Nd‐doped GaN powders are synthesized by a direct nitridation of Ga₂O₃, and the structural, optical, and magnetic properties of the products with different Nd concentrations are investigated. It is found that the Nd‐doped GaN powders have wurtzite structure and exhibit a broad blue emission related with defects. The stable room‐temperature ferromagnetism is observed in the products, which is dependent on the Nd concentration. The possible origin of the ferromagnetism is discussed.     

掺氟氧化锡纳米粉体的制备

以无机盐为前驱物采用改进的溶胶凝胶法制备了掺氟氧化锡的纳米粉末,用TEM和XRD对不同热处理温度的粉体进行了形貌和结晶状态表征,并研究了粉体的特性。     

Structural and Magnetic Property of Co1‐xNixFe2O4 Nanoparticles Synthesized by Hydrothermal Method

The cobalt nickel ferrite (Co_1‐xNi_xFe₂O₄ x = 0–1.0) nanoparticles were synthesized by a hydrothermal method. Effects of nickel content and organic template on the microstructure and magnetic property of the nanoparticles were studied. The experimental results indicate that Ni²⁺ substitution for Co²⁺ and special synthesis technique leads to obvious change in microstructure and magnetic property of the ferrites. The ferrites show nonlinear variations in the saturation magnetization and the coercivity with nickel substitution, which are explained by shape anisotropy and supernormal cation distribution. The organic template also leads to variation in the microstructure and properties of the nanoparticles.     

Structural and Optical Characteristics of Crystalline Silicon Carbide Nanoparticles Synthesized by Carbothermal Reduction

Silicon carbide (SiC) nanoparticles were successfully synthesized by using carbothermal reduction method. Nanoparticles with zincblende structure (3C–SiC) could be prepared using polysiloxane as silicon source and phenol resin (MH) or xylene resin (YN) as carbon source. The sample YN has an average grain size of 22 nm, larger than that of the sample MH (8 nm). Raman spectroscopy revealed that all nanoparticle samples contain graphitic surface carbon layers. Oxygen contamination on the nanoparticle surface could be reduced by postfluorine treatment (MH-F). But the sample MH-F showed reduced SiC crystallinity compared with the sample MH. The nanoparticle samples exhibited an intensive emission band in the blue region observed by photoluminescence (PL) spectroscopy. The band-gap energy of the nanoparticle samples is estimated to be ∼3 eV from the PL spectra, blueshifted by ∼0.6 eV from that of bulk 3C–SiC due to the quantum confinement effect.     

Microstructure and Dielectric Properties of Nickel‐Doped Ba0.7Sr0.3TiO3 Ceramics Fabricated by Solgel Method

A study of phase transition, microstructure, and dielectric properties of Ba_0.7Sr_0.3Ti_1–xNi_xO₃ (BSTN) ceramics prepared by slow‐injection solgel technique with x ranging from 0 to 1 mol% is reported in this article. The as‐prepared BSTN material was calcined at 800 and 1000°C and subsequently sintered at 1100 and 1200°C, respectively. The optimized condition was found to be Ba_0.7Sr_0.3TiO₃ doped with 1 mol% nickel calcined at 1000°C and sintered at 1200°C having the lowest dielectric loss of 0.02 with a dielectric constant of 1603 which was measured at a frequency of 1 kHz at room temperature.     

Highly Efficient Room Temperature Synthesis of Silver‐Doped Zinc Oxide (ZnO:Ag) Nanoparticles: Structural,Optical, and Photocatalytic Properties

Synthesis of silver‐doped zinc oxide (ZnO:Ag) nanoparticles through precipitation method has been reported. The synthesis was conducted at room temperature and no subsequent thermal treatment was applied. ZnO nanoparticles were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), fourier transmission infrared spectroscopy (FTIR), and ultraviolet‐visible (UV–Vis) spectroscopy. Detailed crystallographic investigation was accomplished through Rietveld refinement. The effect of silver content on structural and optical properties of resultant ZnO nanoparticles has been reported. It was found that silver doping results in positional shifts for the XRD peaks and the absorption band edge of ZnO. These were attributed to the substitutional incorporation of Ag⁺ ions into Zn²⁺ sites within the ZnO crystal. In addition, higher silver incorporation resulted in smaller size for ZnO nanoparticles. The photocatalytic activity of the ZnO:Ag nanoparticles was also determined by methylene orange (MO) degradation studies and compared to that of undoped ZnO. Improved photocatalytic activity was obtained for ZnO:Ag nanoparticles. It has been shown that an optimum amount of silver dopant is required to obtain maximum photocatalytic activity.     

Photocatalytic Activity of Pure and Zinc Doped Tin Oxide Nanoparticles Synthesized by One Step Direct Injection Flame Synthesis

A very simple and rapid Direct Injection Flame Synthesis (DIFS) method is effectively used to synthesize pure tin oxide (SnO₂) and zinc doped tin oxide (Zn:SnO₂) nanoparticles from the metallic tin (Sn) and zinc (Zn) powders for the photocatalytic degradation of methylene blue (MB) dye. The DIFS nanoparticles were characterized using XRD, Raman, UV–Vis, FESEM, PL and EDX studies. The X-ray diffraction analysis indicated that the synthesized SnO₂ and Zn:SnO₂ nanoparticles have pure tetragonal phases and their average crystallite size decreases when Zn was doped with SnO₂. Raman study confirmed the various mode of vibrations and the crystal structure of the synthesized nanoparticles. Purity, atomic percentage and chemical composition were analysed using Energy dispersive X-ray analysis and found to be free from impurities. The band gap energy increases from 3.5 to 3.6 eV upon doping which was revealed from the UV–Visible spectroscopic analysis. Photoluminescence analysis confirms the red shifted emission for Zn:SnO₂ due to the oxygen deficiency. The CIE chromaticity (x,y) for SnO₂ and Zn:SnO₂ was calculated from the emission spectra and the co-ordinates represents blue and violet region respectively. Field Emission Scanning Electron Microscopy analysis showed that the pure SnO₂ nanoparticles have irregular, agglomerated, nanoflowered and nanoclustered formation whereas Zn:SnO₂ nanoparticles has more crystalline, cubical and nanoflake structure. The photocatalytic activity was enhanced due to the presence of Zn in SnO₂ under UV light irradiation. The efficiency of MB degradation by SnO₂ was found to be 82% and enhanced to 88% upon doping. Thus the Zn doped SnO₂ nanoparticles synthesized by DIFS was found to be an effective photocatalyst than the pure SnO₂.

     

New Hydrolytic Process for Producing Zirconium Dioxide, Tin Dioxide, and Titanium Dioxide Nanoparticles

Nanocrystalline ZrO₂, SnO₂, and TiO₂ were synthesized through a simple hydrolytic process based on the etherification of alcohols. The obtained products had good uniformity and were less aggregated than in other synthesis techniques. The synthesis of ZrO₂ and SnO₂ in this process was dependent mainly on the reaction temperature, whereas the morphologies of TiO₂ exhibited a dependence on the alcohols used.     

Investigation of Structural and Optical Properties of Graphene Oxide-Coated Neodymium Nanoparticles Doped Zinc-Tellurite Glass for Glass Fiber

Journal of Inorganic and Organometallic Polymers and Materials - Carbon-based materials such as graphene oxide are known as attractive candidate to improve the current optoelectronic and laser...     

Bismuth‐Doped Multicomponent Optical Fiber Fabricated by Melt‐in‐Tube Method

Bismuth‐doped multicomponent optical fiber was fabricated by a melt‐in‐tube method. The fiber was prepared at drawing temperature where the clad was softened, while the fiber core glass was melted. The obtained fiber was characterized by electroprobe microanalyzer and X‐ray diffraction. No obvious precipitation of crystals or bismuth metals was observed in the fiber. Excited by 808‐nm laser, intense broadband near‐infrared emission with full width at half maximum of about 325 nm was observed from the fiber. Consequently, this fiber is promising for broadband fiber amplification. The melt‐in‐tube method is generally applicable for fabricating bismuth‐doped multicomponent optical fiber.     

Magnetic Properties of Annealed CoFe2O4 Nanoparticles Synthesized by the PEG-Assisted Route

Annealed cobalt inverse spinel-type ferrite nanoparticles were synthesized using polyethylene glycol assisted co-precipitation. The structure, magnetic properties and effect of annealing temperature was investigated in detail. Saturation magnetization, coercivity and remanence magnetization were observed to decrease with increasing temperature. The magnetic hysteresis curves supported the proposition that the CoFe₂O₄ nanoparticles showed ferromagnetic character from 10 to 400 K. Magnetization measurements showed the blocking temperature to be higher than 400 K. Unsaturated magnetization behavior suggested the existence of disordered spins in the surface layer of the CoFe₂O₄ nanoparticles.     

Size and Shape Tailoring of Titania Nanoparticles Synthesized by Solvothermal Route in Different Solvents

A simple solvothermal low‐temperature synthesis process of TiO₂ nanoparticles was investigated in different solvents [Octanol (Oc), Ethanolamine (Am) and Terathane (Tr)] with titanium (IV) chloride (TiCl₄) as precursor. The samples were characterized by X‐Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). XRD showed the crystallite size ranging from 4 to 12 nm, which were calculated using Debye–Scherrer's equation. The existence of poor or high crystalline anatase phases and high crystalline anatase/rutile mixture was also shown. TEM images displayed variations in the morphological behavior depending on the synthesis condition. Particles of irregular morphology with high irregular agglomeration up to well‐defined particles can be observed, which are self‐assembled by oriented attachment (OA). This self‐assembly led to TiO₂ microparticles with 3‐D Wulff shape for anatase and 1‐D shape for rutile. The results showed that the TiO₂ nanopowder could be easily engineered and adapted by the solvent type, the TiCl₄ concentration and the synthesis time.     

Magnetic Properties of FePt Nanoparticles Prepared by a Micellar Method

FePt nanoparticles with average size of 9 nm were synthesized using a diblock polymer micellar method combined with plasma treatment. To prevent from oxidation under ambient conditions, immediately after plasma treatment, the FePt nanoparticle arrays were in situ transferred into the film-growth chamber where they were covered by an SiO₂ overlayer. A nearly complete transformation of L1₀ FePt was achieved for samples annealed at temperatures above 700 °C. The well control on the FePt stoichiometry and avoidance from surface oxidation largely enhanced the coercivity, and a value as high as 10 kOe was obtained in this study. An evaluation of magnetic interactions was made using the so-called isothermal remanence (IRM) and dc-demagnetization (DCD) remanence curves and Kelly–Henkel plots (ΔM measurement). The ΔM measurement reveals that the resultant FePt nanoparticles exhibit a rather weak interparticle dipolar coupling, and the absence of interparticle exchange interaction suggests no significant particle agglomeration occurred during the post-annealing. Additionally, a slight parallel magnetic anisotropy was also observed. The results indicate the micellar method has a high potential in preparing FePt nanoparticle arrays used for ultrahigh density recording media.     

Structural Characterization and Optical Properties of Perovskite ZnZrO3 Nanoparticles

Perovskite ZnZrO₃ nanoparticles were synthesized by hydrothermal method, and their microstructures and optical properties were characterized. The crystallinity, phase formation, morphology and composition of the as‐synthesized nanoparticles were characterized by X‐ray diffraction (XRD), selected area electron diffraction (SAED), high‐resolutiontransmission electron microscopy (HRTEM), and energy‐dispersive X‐ray (EDX) spectroscopy analysis, respectively. TEM images demonstrated that the average particle size of the ZnZrO₃ powders was increased with increasing the Zn/Zr molar ratios in the precursors, and more large ZnZrO₃ particles with cubic morphology were observed at high Zn/Zr molar ratios. In addition, the phase structures of the ZnZrO₃ particles were also evolved from a cubic to tetragonal perovskite phase, as revealed by XRD and SAED patterns. HRTEM images demonstrate that surface structures of the ZnZrO₃ powders synthesized at high Zn/Zr molar ratios, are composed of corners bound by the {100} mini‐facets, and the surface steps lying on the {100} planes are frequently observed, whereas the (101) facet isoccasionally observed. The formation of such a rough surface structure is understood from the periodic bond chain theory. Quantitative EDX analyses demonstrated that the atomic concentrations (at.%) of Zn:Zr:O in the particles were 20.70:21.07:58.23, as close to the composition of ZnZrO₃. In the optical spectra, a significant red shift of the absorption edges (for the ZnZrO₃ nanopowders) from UV to visible region (from 394 to 417 nm) was observed as increasing the Zn/Zr molar ratios in the precursors, which corresponds to that the band gap energies of the ZnZrO₃ nanopowders can be continuously tuned from 3.15 to 2.97 eV. This opens an easy way to tune the band gap energies of the ZnZrO₃ nanopowders.     

Sodium‐Doped ZnO Nanowires Grown by High‐pressure PLD and their Acceptor‐Related Optical Properties

Sodium‐doped ZnO (ZnO:Na) nanowires were grown with a high‐pressure pulsed‐laser deposition process on silicon substrates using sputtered gold particles as catalysts. The introduction of sodium dopants into ZnO nanowires was confirmed by both X‐ray diffraction spectrum and X‐ray photoelectron spectroscopy. The morphology and microstructural changes in ZnO nanowires due to sodium doping were investigated with scanning electron microscope, high‐resolution transmission electron microscope, and Raman spectrum. Detailed photoluminescence studies of ZnO:Na nanowires revealed characteristic sodium acceptor‐related peaks, for example, neutral acceptor‐bound exciton emission (A⁰X, 3.356 eV), free‐to‐neutral‐acceptor emission (e, A⁰, 3.314 eV), and donor‐to‐acceptor pair emission (DAP, 3.241 eV). This indicated that sodium doping induces stable acceptor level with a binding energy of 133 meV in ZnO:Na nanowires.     

Characterization of Nickel Ions in Nickel‐Doped Yttria‐Stabilized Zirconia

The distribution of Ni²⁺ ions in NiO‐doped 10YSZ powder is examined with Superconducting Quantum Interference Device magnetometry, a technique that is able to distinguish between randomly distributed Ni²⁺ ions in solid solution and ordered Ni²⁺ ions within NiO with high precision. Very high purity powders containing 0.01, 0.1, 0.5, and 1.0 mol% NiO in 10YSZ (all levels below the solid solubility limit of NiO in 10YSZ) were made from acetate precursors and a modified EDTA (ethylenediaminetetraacetic acid)‐citrate synthesis method. The powders were calcined in air at either 873 or 1273 K. The 873 K calcination leads to single phase YSZ particles about 10 nm in diameter, and almost all of the NiO dopant exists in complete solid solution. The 1273 K calcination leads to a larger YSZ particle size (55–95 nm), and also to the formation and/or growth of NiO particles, the amount of which depends on the length of time of calcination. Upon sintering the powders in air (1773 K, 1 h), the NiO dissolves back into 10YSZ. The results demonstrate that particle growth during calcination leads to the exsolution of Ni²⁺ ions to form NiO. This has important implications for the synthesis of NiO‐doped 10YSZ from chemical precursors.     

二氧化锡电极的电阻率测试及电性能研究

介绍了二氧化锡电极的电阻率测试方法,实测了国产二氧化锡电极在使用前后电阻率的变化。发现使用后二氧化锡电极的电阻率会增大,XRD衍射以及电镜分析表明,使用后的电极其晶粒会随温度升高而增大,晶粒之间的晶界也变大,因而使电阻率增加。     

Camphor Sulfonic Acid Doped Polyaniline-Titanium Dioxide Nanocomposite: Synthesis,Structural, Morphological,and Electrical Properties

A nanocomposite of polyaniline-titanium dioxide (PANi-TiO₂, 50 wt%) was doped with camphor sulfonic acid (CSA) by solid state reaction with increasing CSA content up to 50 wt% in a smooth agate mortar. CSA doped PANi-TiO₂ was dissolved in m-cresol and films were cast using a spin-coating technique. The doping effect of CSA on PANi-TiO₂ nanocomposite was characterized and evaluated by X-ray diffraction pattern (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and electrical conductivity measurement. The XRD spectra showed that the addition of CSA has no effect on crystallinity of PANi-TiO₂. SEM studies revealed that CSA has a strong effect on morphology of PANi-TiO₂. The FTIR spectra revealed the interaction between CSA and PANi-TiO₂ nanocomposite. Electrical conductivity measurements indicated that with the increasing content of CSA, the conductivity shows an orderly increase.     

掺偶氮苯二氧化钛基复合薄膜的制备及光开关性能

通过低温溶胶-凝胶技术结合旋涂法制备了掺偶氮苯二氧化钛基有机-无机复合薄膜.研究了不同热处理温度对复合薄膜的表面形貌、传输模式、折射率与厚度和光化学结构特性的影响.结果表明:该复合薄膜在低于300℃的热处理温度时表面光滑致密、折射率可调,是良好的光波导材料.通过测试样品在365 nm紫外光和450 nm可见光照射下的吸...