Materials Science Forum Vols. 663-665

Abstract: With the help of impedance spectroscopy, the complex impedances of three kinds of ultrafine LaF3 polycrystalline powders (industrial grade LaF3 polycrystalline powder, ultrafine LaF3 polycrystalline powder prepared with sol-gel technique, and ultrafine LaF3 polycrystalline powder prepared with microwave method) were measured, and their ionic conductivities were derived. It is found that the ionic conductivities of the industrial grade LaF3 polycrystalline powder and the ultrafine LaF3 polycrystalline powder prepared with microwave method are higher than that of the ultrafine LaF3 polycrystalline powder prepared with sol-gel technique.

Abstract: The effects of dopant 5-sulfosalicylic acid on the conductivity of polypyrrole were investigated. Under the condition of fixed molar ratio of oxidant-to-monomer (0.75: 1.00), a dozen of polypyrrole samples were made from chemical polymerizing the monomer pyrrole in aqueous medium by varying the dopant-to-monomer molar ratio. It was found that the dopant affected the conductivity and particle size of the synthesized polypyrrole. A maximum value for electrical conductivity of 5575 S/m was achieved when the molar ratio of dopant: oxidant: monomer is 2.25:0.75:1.00.

Abstract: Conductive polyaniline/cerium dioxide (PANI/CeO2) composites have been synthesized by in-situ polymerization of aniline in the presence of CeO2 nanoparticles. The structure and thermal stability of obtained composites were characterized by Fourier-transform infrared spectra (FTIR), Fourier-transform Raman spectra (FT-Raman), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The results showed that PANI and CeO2 nanoparticles were not simply blended, and a strong interaction existed at the interface of CeO2 and PANI. In the PANI/CeO2 composite, the degree crystallinity of PANI increased and diffraction pattern of CeO2 was amorphous. And that the composites were more thermally stable than that of the pure PANI. Electrical conductivity measurements indicated that the conductivity of PANI/CeO2 composites was much higher than that of the pure PANI and the maximum conductivity obtained was 11.68 S/cm at 17.5 wt% of CeO2.

Abstract: CdS, a bright yellow precipitate is well known for its optical, electrical, electro-optical and photochemical properties. CdS has also been prepared in the interlayer spaces of layered materials such as laponite and montmorillonite (bentonite). Several properties of intercalated CdS have been studied, but for the best of our knowledge there is no reports on its use. In this work, we applied CdS-intercalated bentonite / carbon composite as an electrode for determination of S2- ion in aqueous solution. CdS- intercalated bentonite was prepared by the in situ solid-solid reaction between Cd(II)-bentonite and Na2S. To construct a potentiometric electrode, CdS-intercalated bentonite was mixed with artificial graphite, polytetrafluoroethylene (PTFE) and carboxymethylcellulose (CMC) in an appropriate ratio. The electrode was used to determine S2- in aqueous solution, graphs of log [S2-] vs measured voltage (mv) gave linear relation up to 3 orders of ion concentrations. Apart from the reproducibility and good precision, the electrode is good for its selectivity, durability and low cost.

Abstract: Fluorine doped tin oxide (FTO) thin films have been developed as alternatives to ITO for thin film transparent electrode applications. In this works, the FTO thin films were deposited using inkjet printing technique since the technique is a promising deposition method to fabricate low-cost devices. The FTO precursor was prepared by reacting SnCl4•5H2O and NH4F at 60oC in a sealed container. The thin films were deposited on glass substrates at 40oC with variations of printing layers. The optical and electrical properties of the films were affected by the number of printed layers. It was observed the four layers film has the optimum optical transmittance and sheet resistance which were 96 %T and 16.4 Ω/□ respectively.

Abstract: Crystal structure and microwave dielectric properties of (Ca1-xSmx) [(Li1/3Nb2/3)0.95Zr0.15]3+δ(0.0≤x≤0.2,CSLNZ) ceramics were investigated. A single phase with orthorhombic perovskite structure was obtained at x=0.0~0.08. With an increase of Sm3+ content, the quality factor value firstly increased, and then began to decrease at x=0.03 due to a decrease of the degree of B-site 1:2 ordering. The variation of τf with tolerance factor was discussed. When x=0.05, the optimum microwave dielectric properties: the permittivity is 32.4，the quality factor is 16560GHz，and the temperature coefficient of resonator frequency is −6.3×10−6/°C。

Abstract: By doping three complex dopants in different molar ratio, a series of polypyrroles doped with 9, 10-anthraquinone-2-sulfonic acid sodium, 5-sulfosalicylic acid and toluene-4-sulfonic acid were synthesized by polymerizing the monomer pyrrole in aqueous solution of ferric chloride. The resulting polypyrroles were characterized with the four-probe and laser light scattering, respectively. Our results indicate that optimized value of conductivity reached to 6683 S/m when the molar ratio of anthraquinone-2-sulfonic acid sodium to 5-sulfosalicylic acid to toluene-4-sulfonic acid was 2:1:3. For applications of polymer in optoelectronics, in lithium-ion battery and in electromagnetic shielding, to obtain optimized value of conductivity has great significance for us.

Abstract: The time-harmonic electromagnetic wave through the one-dimensional photonic crystals (1-D PCs) perpendicularly has been considered. By theoretical calculation with characteristic matrix method, the dispersion curves and the transmittance spectra were calculated. From the dispersion curves, it shown that the lowest band gap is at frequencies between 0.23~0.32, i.e. it is around 0.27. In addition, according to the transmittance spectra, it shown that the transmittance declined from 40.6% to 0 dramatically along with the periodicity N of the periodically stratified medium increased from 2 to 1024, it also exhibited that when the periodicity N was upped to 8, it could form 1-D PCs.

Abstract: Photonic crystal fiber (PCFs) offer new possibilities of realizing highly birefringence fibers due to a higher intrinsic index contrast compared to conventional fibers. Here, based on general section structure of PCFs, we take some mend in the core configuration, and achieve highly birefringence effect. A elliptic air hole and its inscribed circular high refractive material form the core of PCFs together. Especially to mention, they are being tangent at two points. By optimally selecting parameters, the effective refractive index difference between two orthogonal directions neff can reach the magnitude of 10-2. After numerical calculation, we find that increase the size of circular solid core, or long axe size of elliptic air hole, birefringence parameter of modal field can become more highly. Moreover, by matching structure parameters appropriately, the modal field diameters can be equivalent in the two orthogonal directions. A Gaussian modal field with highly birefringence character can be acquired.

Abstract: The transmittance spectra of one-dimensional photonic crystals (1-D PCs) with single defect in different location have been calculated. Defined the parameter N as the number of the layers located to the left of the single defect, set 13 as the number of the total layers of the 1-D PCs included the defect, during the course of the number of N increased from 0 to 12, as it upped to 3, there occurred defect band gap in the stop band gap, and when N upped to 12, the defect band gap disappeared; besides, the defect band gap is at frequencies between 0.3000~0.3090, most of them are at the frequencies around 0.3020. In addition, the transmittance has a turning point at the parameter N=7, that is to say, there has an approximate symmetry in transmittance when the parameter N increased from 3 to 11.