High resolution electron microscopy of bismuth oxides with perovskite layers

Layered bismuth oxides of the general formula (Bi₂O₂)²⁺ (A _n−1B_nO_3n+1)²⁻ whereA = Bi or Ba,B = Ti, Fe, W andn = number of perovskite layers have been investigated by high resolution electron microscopy. Lattice images obtained forn = 1 to 6 members show stacking of (n − 1) perovskite layers sandwiched between dark bands due to the (Bi₂O₂)²⁺ layers. It has been possible to resolve the perovskite layer structures in some of the oxides. A highly ordered structure is observed upto then = 3 member, whereas higher members show superstructures, dislocations and stacking faults arising from the side-stepping of (Bi₂O₂)²⁺ layers as well as ferroelectric domain walls. Contribution No. 73 from Materials Research Laboratory.     

A Green Chemical Synthesis and Characterization of Mn3O4 nanoparticles

Mn₃O₄ nanoparticles were synthesized via an ionic liquid (IL) assisted process at room temperature, which is rather difficult to achieve by other techniques. The synthesized product was characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, thermal gravimetry (TG), and vibrating sample magnetometry (VSM). The prepared material showed a high purity, while crystallite size and particle size agree well with each other, 17±2 and 19±3?nm, respectively, revealing nearly single crystalline character of nanoparticles. The product contains 4?wt% of adsorbed water and ionic liquid. This method provides a facile, one-step, and low-cost route for the synthesis of nanostructures of metal oxides. In addition, [BMIM]BF₄ could be collected and reused for subsequent reactions.     

H2O2-assisted structural transformation of Mn3O4 nanoparticles to nanorods for supercapacitor applications

Journal of Materials Science: Materials in Electronics - Utilizing Manganese Chloride tetra hydrate as a precursor, Pure and H2O2-assisted Mn3O4 were synthesized using a facile hydrothermal...     

Local structure modulation of the low La-doped layered strontium manganite Sr4Mn3O10 studied by transmission electron microscopy and electron energy-loss spectroscopy

Transmission electron microscopy (TEM) and electron energy-loss spectroscopy (EELS) have been used to characterize the structure and microstructure of the low La-doped layered manganite La _x Sr_4−x Mn₃O₁₀ (x ≤ 0.15). The structure of the perfect phase has been identified as an n = 3 layered structure of the hexagonal series by electron diffraction (ED), high-resolution electron microscopy (HRTEM) together with numerical image simulations. The presence of local superstructure modulation associated with La ordering in the compounds was revealed by electron diffraction and high-resolution electron microscopy. Electron diffraction data indicate that this superstructure modulation is two-dimensional, and the modulation plane lies in the ac plane. The two primary modulation vectors are and In addition, another type of modulated structure associated with periodic lattice distortion was occasionally visible in the La_0.15Sr_3.85Mn₃O₁₀ phase. Energy-loss spectroscopy data indicate that the periodic lattice distortion is led by ordered oxygen deficiency.     

Valence determination of titanium and iron using electron energy loss spectroscopy

A method of determining the valence state of titanium and iron in ceramic materials using the electron energy loss spectroscopy is given. In this method the L _2,3 loss edges of a standard are determined and the unknown valence state is determined by observing its spectrum and comparing it to the established standard.     

Optical properties of metallic nanowires by valence electron energy loss spectroscopy

The determination of intrinsic conductivity of nanowires (NWs) is essential to understand the charge transport behaviour involved in hybrid nanocomposites. These high conductive metallic fillers are good candidate to improve electrical properties of composites in aeronautic industry. The main difficulty is often to achieve the combination of both high spatial resolution and information on the physical properties as electrical conductivity. One of the suitable methods to give the desired information is electron energy loss spectroscopy (EELS) in scanning transmission electron microscopy (STEM) mode, especially in the low-loss region. This is demonstrated by studying the nickel and gold nanowire.     

Structural transformation from Mn3O4 nanorods to nanoparticles and band gap tuning via Zn doping

Synthesis of undoped and Zn doped hausmannite Mn₃O₄ nanorods was achieved through a simple hydrothermal route. Scanning electron microscopic studies showed that due to in situ Zn doping a structural deformation from Mn₃O₄ nanorods to a mixture of Mn₃O₄ nanorods and nanoparticles occurred. The amount of nanoparticles in the mixture increased with the increase of doping percentage. X-ray diffraction studies, transmission electron microscopy and selected area electron diffraction pattern revealed that both the nanorods and the nanoparticles were hausmannite Mn₃O₄. X-ray photoelectron spectroscopic studies confirmed successful zinc doping in Mn₃O₄. Microscopic studies revealed that the average diameters of Mn₃O₄ nanorods and nanoparticles were of 200 nm and 70 nm, respectively. The possible growth mechanism and the reasons behind the formation of nanoparticles along with nanorods are discussed briefly. UV–vis spectroscopic studies showed a continuous increase in the energy bandgap of Mn₃O₄ with the increase in Zn doping percentage.     

Auger electron spectroscopy and electron energy loss spectroscopy studies of the formation of silicon nitride by implanting low energy nitrogen ions into silicon

Thin (d ? 10 nm) films of almost stoichiometric silicon nitride were prepared by implanting nitrogen ions with energies below 5 keV into silicon with subsequent thermal annealing. A combination of Auger electron spectroscopy (AES) and electron energy loss spectroscopy (ELS) was used to determine the chemical composition and to investigate the chemical bonding states of the thin films. The spectra are in good agreement with those obtained for Si₃N₄ produced by chemical vapour deposition. The use of AES and electron ELS allowed the stepwise formation of the SiN bonds to be investigated for the first time, and hence further information about the electronic structure of Si₃N₄ was obtained. Depth-concentration profiles for nitrogen are presented.     

A brief review of quantitative aspects of electron energy loss spectroscopy and imaging

Abstract

This review addresses a number of aspects of electron energy loss spectroscopy (EELS) for quantitative analysis, including: procedures for the quantification of EELS elemental analysis and mapping with an indication of the accuracies and detection sensitivities; procedures for the extraction of valence band electronic structures using low loss spectroscopy; and an outline of methods available for the quantitative determination of local valencies, coordinations, and bond lengths of atomic species using electron loss near edge and extended fine structures (ELNES and EXELFS). Additionally, a number of applications of quantitative EELS in spatially resolved studies of interfaces and defects are highlighted.     

A room temperature synthetic route to Mn3O4 nanoplates

Nanoplates of Mn3O4 were prepared by redox reactions of Mn(CH3COO)2 x 4H2O taking place in short chain n-alkylamine aqueous solutions such as n-butylamine, n-propylamine and n-hexylamine at room temperature. Phase purity was confirmed by powder X-ray diffraction. The high resolution transmission electron microscopy revealed the rectangle shape of Mn3O4 nanoplates with the average edge length of 22 nm and width of 19 nm. The prepared Mn3O4 nanoplates exhibited a coercive field of 5034 Oe at 10 K. The possible formation mechanism was also discussed.     

Controlled synthesis of manganese oxohydroxide (MnOOH) and Mn3O4 nanorods using novel reverse micelles

Novel reverse micelles of high CTAB concentration were successfully developed to synthesize MnOOH (manganese oxyhydroxide) nanorods with uniform diameters of about 10 nm and up to 200 nm in length under mild solution conditions and Mn3O4 nanorods with the same morphology could be obtained by calcining the precursors at 450 degrees C. The morphology and microstructure of the nanorods were investigated by transmission electron microscopy (TEM and HRTEM), XRD and TGA. The results showed that the concentration of CTAB was a key factor for the formation of MnOOH nanorods and only above 0.2 M the nanorods could be obtained. Moreover, the length of nanorods increased with the increase of CTAB concentration, while the diameter of nanorods retained steadily. In this way, the length of nanorods could be easily controlled from tens nanometers to hundreds nanometers by increasing the CTAB concentration from 0.35 M to 1.25 M. In addition, in our experiment the products were almost entirely rod-like shape, which indicated this method should be suitable for mass-producing.     

The electron paramagnetic resonance of manganese in Mo1−x Ga4Mn x

We report the results of electron paramagnetic resonance experiments on managanese dissolved in MoGa ₄ over the temperature range 293-1.8 K. It is found that both theg shift and the line width show an anomalous sharp concentration independent increase as the temperature is decreased from 100 to 4.2 K. The experimental results for the relaxation rate andg shift are analyzed in terms of currently available theories and found to be unexplained by them. A model is proposed for the alloys invoking a bottleneck effect at high temperatures which breaks down at low temperatures due to the onset of a Kondo effect. When the bottleneck effect is broken down it is suggested that the theories for the unbottlenecked regime again become applicable.One of us (W.Z.) would like to acknowledge the support of a maintenance grant from the Fonds National Suisse.     

一步合成Mn3O4@RGO复合材料及其非对称超级电容器的应用

在乙醇胺和水组成的混合溶剂中, Mn(Ac)₂与氧化石墨烯一步反应得到还原石墨烯(RGO)与黑锰矿纳米颗粒(Mn₃O₄)组成的复合材料Mn₃O₄@RGO。以Mn₃O₄@RGO为正极, RGO为负极, 组装得到了具有优良储能性能的非对称型超级电容器Mn₃O₄@RGO//RGO。基于活性物质的总质量, 电容器的最大能量密度可达21.7 Wh/kg, 相应的功率密度为0.5 kW/kg; 同时, 最大功率密度为8 kW/kg时, 对应的能量密度为11.1 Wh/kg。Mn₃O₄@RGO//RGO还表现出良好的循环稳定性, 在经历5000次循环后, 比电容依然保持88.4%。电容器的良好储能性能可归因于在RGO表面生长的高密度Mn₃O₄纳米颗粒和RGO的良好导电性能。     

Bandgap determination of P(VDF-TrFE) copolymer film by electron energy loss spectroscopy

The ferroelectric β of poly(vinylidene fluoride trifluoroethylene), P(VDF-TrFE) is confirmed for 100 nm thickness spin coated copolymer film. The homogeneous coverage of the copolymer film is investigated by the help of X-ray photoelectron spectroscopy (XPS). Most importantly, the existing bandgap in the crystalline phase of the copolymer is determined directly from the electron energy loss spectroscopy (EELS).     

Synthesis and characterization of Mn2O3 nanorods using a novel manganese precursor

The Mn₂O₃ nanorods have been prepared using [Mn(sal)₂] complex as a novel precursor in the presence of sodium dodecyl sulfate (SDS) as surfactant. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) spectroscopy. Manganese oxide nanocrystals have been prepared under different condition. The controlled experimental results showed that the ultrasonic irradiation and the use of SDS as the surfactant in the chemical process play important role in the formation of the final products.