Materials Science Forum Vols. 663-665

Abstract: The utilization of zinc anode for zinc-based battery is limited due to low cycling life, shape change and ZnO passivation on the electrode surface. The electrochemical behavior of zinc anode in the presence of the additives added to the electrodes or the electrolytes have been reported. In this work, LaCoO3 was used as an additive to improve the electrochemical properties of the zinc oxide anode. LaCoO3 synthesized by sol gel method (Schiff base complex) was added to zinc oxide powder (99.9%) with the weight ratio of 1:0.001, 1:0.002 and 1:0.003. The relative ZnO/LaCoO3 ratios were confirmed by particle induced x-ray emission (PIXE) technique.The electrochemical behavior of the ZnO/LaCoO3 electrodes in 6M KOH solution were investigated by voltammetry and electrochemical impedance spectroscopy (EIS). The cyclic voltammogram showed that ZnO/LaCoO3 gave higher anodic current and ZnO passivation delayed. The EIS spectra showed that charge transfer resistances of the ZnO/LaCoO3 anodes due to zinc oxidation were higher than that of ZnO electrode

Abstract: Microcrystalline silicon (μc-Si:H) film deposited on silicon oxide in a very high frequency plasma enhanced chemical vapor deposition with highly H2 dilution of SiH4 has been investigated by Raman spectroscopy and high resolution transmission electron microscopy. Raman spectroscopy results show that the crystalline volume fraction increases with increasing the hydrogen flow rate and for the hydrogen flow rate of 160 sccm, the crystalline volume fraction reaches to 67.5%. Nearly parallel columnar structures with complex microstructure are found from cross-sectional transmission electron microscopy images of the film. The temperature depend dark conductivity and activation energy are studied in order to investigate the electronic transport processes in the nc-Si films.

Abstract: The influence of molecular compression on the electron transport through single alkandithiol molecules sandwiched between two gold (111) electrodes has been studied by nonequilibrium Green’s function technique combined with density functional theory. The results showed that the molecular compression may increase the molecular current under low bias while decrease the molecular current under high bias. The mechanism of the effect of molecular compression on the electron transport behavior has been discussed in terms of electronic structures and transmission spectra.

Abstract: The effects of Li2CO3-V2O5 (LV) co-doped on the sinterability, phase compositions and microwave dielectric properties of 0.6Mg4Nb2O9-0.4SrTiO3 composite ceramics have been investigated. All specimens were prepared by solid-state reaction method and sintered at 1050-1200oC for 5h. With an amount LV addition, the densification sintering temperature is significantly lowed from 1300oC to 1175oC. The non-stoichiometric compounds Sr(NbTi)O3+δ and Mg4(Nb1-xTix)2O9-δ were confirmed by X-ray diffraction and energy dispersive X-ray analysis. For the specimen with 1.5 wt% LV addition sintered at 1175oC for 5 h exhibited dielectric properties: εr=20.1, Q•f=10 240 GHz, τf =0.15 ppm/oC.

Abstract: Er2O3 films were deposited on Si(001) substrates by radio frequency magnetron technique. X-ray photoelectron spectroscopy, x-ray diffraction and atomic force microscopy show the Er2O3 films obtained are stoichiometric, amorphous, and uniform. The electronic structure is studied which shows a large energy gap value of the Er2O3 film, indicating Er2O3 film could be a promising antireflection coating for solar cells.

Abstract: The nonequilibrium Green’s function approach in combination with density-functional theory is used to perform ab inito quantum-mechanical calculations of the electron transport properties of porphyrin oligomers sandwiched between two gold electrodes. The results show that porphyrin oligomers are good candidates for long-range conduction wires. In particular, the decay of conductance of porphyrin oligomers does not follow the exponential relation. The electron transport behavior was analyzed from the molecular projected self-consistent Hamiltonian states and the electron transmission spectra of the molecular junctions.

Abstract: Based on the oxygen ion conductor La2Mo1.5W0.5O9, a series of Ag2O doped samples La2Mo1.5W0.5O9/Ag were prepared with conventional solid-state reaction method. The effects of Ag2O doping on the microstructure and electrical conductivity have been investigated by XRD, FESEM and direct current conductivity measurements. With the increase of Ag2O doping, the grain was further refined and compacted, meanwhile, Ag diffusion distribution in the form of second-phase appear at grain boundary. The sample density and conductivity also gradually increased with the increasing of doping amount. The conductivity of the composite specimen La2Mo1.5W0.5O9 /Ag has a great enhancement when the concentration of Ag2O is around 27 wt%, which is eight times higher than that of the single-phase sample.

Abstract: Undoped high quality polycrystalline diamond films were grown by the microwave plasma chemical vapor deposition (MPCVD) method. The effects of hydrogen plasma treatment and vacuum annealing process on the p-type behavior of diamond films were investigated by the Hall effect method. The sheet carrier concentration increased and the sheet resistivity decreased with the treating time of hydrogen plasma and a stable value was achieved finally. After annealing the samples in vacuum at temperature above 600 °C, the sheet carrier concentration dropped dramatically. The origin of this hydrogen terminated p-type conductive layers is also discussed.

Abstract: The effects of ZnO-B2O3-Na2O(ZBN) glass on the sinterability and microwave dielectric properties of Ca[(Li1/3Nb2/3)0.8Sn0.2]O3−δ−0.1TiO2 (CLNS−0.1TiO2) ceramics were investigated . ZBN glass doping can effectively reduce sintering temperatue by 100~150°C. The temperature coefficient of resonator frequency τf increased with an increase of ZBN glass content and sintering temperatue. When ZBN glass of 3wt% were added, the optimum microwave dielectric properties: εr =28.8,Qf =10960GHz and τf = − 7.5×10−6/°C were obtained at the sintering temperature of 1050°C.

Abstract: High-quality 5% W- and Gd-doped La2Mo2O9 nanocrystalline films were successfully synthesized on poly-alumina substrates via a PVP-assisted sol-gel method with inorganic salts as precursors, combined with the rapid thermal annealing and novel three stages annealing procedures. Dense and uniform La2Mo2O9-based films with 90 nm in grain size and 1 μm in thickness were obtained by only twice spin coatings and sintering at 600 oC. The electrical conductivity of the films at 600 oC reaches 0.028 and 0.025 S/cm for W- and Gd-doped samples, respectively.