Key Engineering Materials Vol. 445

Abstract: Spherical La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM) precursor powders were synthesized by aerosol plasma pyrolysis using an aqueous solution of metal nitrate. As-prepared powders obtained by this method were found to have a spherical morphology with a bimodal size distribution of nanosized (primary) and submicron-sized (secondary) particles. The average size of the primary particles was less than 100 nm. X-ray diffraction (XRD) patterns showed that as-prepared powders crystallized to LSGM and other phases. XRD revealed that LSGM pellets were crystallized to a perovskite structure after sintering at 1300 °C for 10 h.

Abstract: La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM) precursor particles were successfully prepared by ultrasonic spray pyrolysis. LSGM thin films were prepared by the electrophoretic deposition (EPD) technique using ethanol containing iodine. The LSGM films were obtained by sintering at 1300 °C for 10 h. The X-ray diffraction patterns revealed that the diffraction peak of LSGM thin films was in agreement with the perovskite structure. The LSGM films attained a uniform thickness of 10 μm.

Abstract: Spherical LiAl0.05Mn1.95O4 precursor powders were successfully prepared by spray pyrolysis. LiAl0.05Mn1.95O4 precursor powders were calcined by 800°C for 10hrs. The particles size, morphology, microstructure, crystal phases of the calcined powders were characterized by X-ray diffraction (XRD) and a scanning electron microscope (SEM). The XRD patterns showed that the crystal phases of the calcined powders were the same as spinel phase (space group: Fd3m). The particles exhibited a spherical morphology with a porous microstructure. The particle size of the primary particles was approximately 200nm. LiAl0.05Mn1.95O4 cathodes exhibited higher rechargeable capacity and cycle stability at high rates. The particle microstructure of LiAl0.05Mn1.95O4 powders was effective for the rechargeable capacity at high rates.

Abstract: Spherical C/LiMn1-XMXPO4 (M=Mg, Zn) cathode materials were successfully prepared by spray pyrolysis. An olivine structure was obtained by heating at 973 K under argon/hydrogen (5%) atmosphere. Citric acid was used as the carbon source. Scanning electron microscopy (SEM) showed that the materials had spherical morphology. The electrochemical properties of the cathode were also estimated by the rechargeable capacity and cycle performance. The first discharge capacity of C/LiMn1-XZnXPO4 (X = 0.1) was approximately 60 mAh/g　at 0.1 C.

Abstract: Palladium (Pd) nanoparticles were prepared on photocatalytic TiO2-coated glass substrate by a photodeposition process and the optical hydrogen sensing properties were examined at room temperature. The TiO2 coatings were prepared on a non-alkaline glass substrate by a sol-gel process and hot water treatment. Pd nanoparticles were deposited on the TiO2 film by photodeposition using UV light. The obtained Pd/TiO2 thin film showed remarkable optical transmittance response to hydrogen gas at room temperature. The normalized transmittance of the Pd/TiO2 thin film at a wavelength of 640 nm decreased to 0.9 on exposing the film to hydrogen gas for only 5 s. This transmittance decrease is considered to be due to a gaschromic effect of the TiO2 photocatalytic coating.

Abstract: The lithium ion conducting properties of lithium- and MⅣ (M = Al, In, Y)-doped zirconium pyrophosphates synthesized via solid state reaction were investigated. The ionic conductivity of the compounds increased with increasing Li content. The activation energy of LixMxZr1-xP2O7 decreased as the lattice parameter increased owing to the enlargement of the size of bottleneck between the cavities. Li0.55(Li0.15Y0.1Zr0.75)P2O7 with a high Li content and a large lattice parameter exhibited a conductivity of 1.7×10-3 S cm-1 at 350 °C, which is sufficient for its application as a solid electrolyte for sensors.

Abstract: Previously, we reported the fabrication of Na0.44MnO2 and LiMn2O4 single crystalline nanowire structure. Moreover, these electrodes showed good high rate property as lithium ion battery, because the nanostructure electrode is suitable for high rate lithium ion battery. Especially, the fabrication of LiMn2O4 single crystalline nanowire was very interesting results because the synthesis of 1-dimesional single crystal structure of LiMn2O4 is very difficult based on cubic crystal structure without anisotropic structure. The LiMn2O4 single crystalline nanowire was obtained thorough the self template method using Na0.44MnO2 nanowire. In this paper, we report the fabrication of Na0.44MnO2 and LiMn2O4 single crystalline nanowire structure and the property of lithium ion battery as review paper.

Abstract: Cathode materials for a lithium-ion battery were prepared using an industrial microwave furnace. The prepared materials were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical properties. Single-phase LiMn2O4 powders could be prepared in a few minutes using an industrial microwave furnace. The obtained results showed that this microwave heating method is a promising industrial technique for efficient preparation of cathode materials.

Abstract: Dye-sensitized solar cells (DSSCs) are one of the promising photovoltaic devices because of their lower manufacturing cost and higher energy conversion efficiency. Wide-gap, porous semiconducting metal oxides are generally used as electrode materials of DSSCs. Previously we utilized ZnO as DSSC electrodes and achieved a high conversion efficiency of 6.58% by improving the structure of ZnO films. However, open-circuit voltage (VOC), one of the factors to determine the performance of DSSCs, was still at a lower level (≈ 0.60 V) than that of common TiO2-based cells. We believe that the lower VOC is due mainly to the occurrence of recombination. In this work, we tried to enhance VOC by controlling the heating process of electrodes and suppressing the recombination for further development of ZnO-based DSSCs. As a result, we have achieved a higher VOC of 0.725 V, confirming that the sintering behavior (grain growth and/or necking of grains) influenced largely the characteristics of DSSCs.

Abstract: Porous nano-scale ZnO particle film was rapidly synthesized from a mixing solution of zinc acetate dihydrate – acetone at about 90 °C. The crystal structure and morphology　were clarified by the X-ray diffraction and a field emission scanning electron microscope. The evaporation of higher vapor pressure acetone resulted in the hydrolysis of zinc salt in itself crystalline water. Three morphologies of ZnO (dispersed nanoparticles, dispersed bread chip-shaped particles and flower-like bread chip-shaped assemblies) were observed.