Electroceramics in Japan X

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Authors: Tomohiro Tabara, Naoki Wakiya, Takanori Kiguchi, M. Tanaka, Kazuo Shinozaki
Abstract: Thin films of HfO2 were fabricated on a p-Si(001) substrate using double pulse excitation (DPE) pulsed laser deposition (PLD) with KrF excimer and Nd:YAG lasers, and using conventional Nd:YAG laser PLD under two typical oxygen pressures (7.3 × 10-2 and 7.3 × 10-1 Pa). At 400°C or higher temperatures, the films are crystalline; at less than 400°C, they are amorphous. At higher oxygen pressures, DPE-PLD was effective against droplets. Then the surface morphology and electrical insulation properties of thin films were improved. At lower pressure, DPE-PLD was ineffective.
Authors: Kaori Nishizawa, Haruhiko Fukaya, Takeshi Miki, Kazuyuki Suzuki, Kazumi Kato
Abstract: A new photochromic ZrO2 precursor solution was prepared using zirconium tetra-n-butoxide, 4-(phenylazo)benzoic acid and ethyleneglycol monomethylether. The density functional theory (DFT) calculation has identified that the structure of the synthesized precursor molecule changed by UV irradiation. The two kinds of thin films were prepared using the photosensitive ZrO2 precursor solution without and with UV irradiation. The surface morphology of thin films changed by UV irradiation. It was found that the surface morphology of thin films is controlled by the difference of precursor structure introduced by UV irradiation.
Authors: Keigo Sato, Shinya Suzuki, Masaru Miyayama
Abstract: The electrochemical properties of titanate nanosheets and layer-structured lithium titanate obtained by restacking of titanate nanosheets were investigated in comparison with those of layer-structured lithium titanate obtained by ion-exchange. Restacked lithium titanate was synthesized by reassembling titanate nanosheets with LiOH aqueous solution. The nanosheets were 50-200 nm wide and 1.7 nm thick. The crystal structure inside the nanosheets was the same as that the of parent material. The oxidation current peaks observed in cyclic voltammograms of titanate nanosheets and restacked material were 1.6 V (Li/Li+), which was lower than that of ion-exchanged material by 0.3 V. The discharge capacity of restacked material was 96 mAh g-1, indicating that 32% of the titanium ions were reduced.
Authors: Hiroshi Marusawa, Yoshinori Saito
Abstract: Barium orthotitanate ceramics (Ba2TiO4) with ≧0.4wt% Nickel shows highly reproducible CO2 absorption - desorption when they are annealed under cyclic temperature conditions. Addition of Ni powder prohibited the grain growth of the Ba2TiO4 ceramic.
Authors: Masahiro Kajitani, Motohide Matsuda, Akinori Hoshikawa, Takashi Kamiyama, Fujio Izumi, Michihiro Miyake
Abstract: The crystal structure and oxide ion conduction properties of La0.9Sr0.1Ga0.9Mg0.1O2.9 were compared with those of LaGa0.8Mg0.2O2.9 with the same oxygen vacancy concentration. Although La0.9Sr0.1Ga0.9Mg0.1O2.9 had a smaller free space through which oxide ions pass compared to LaGa0.8Mg0.2O2.9, the activation energy of oxide ion conduction in the former was lower. This was attributed to the large displacement of La and Ga in La0.9Sr0.1Ga0.9Mg0.1O2.9. The GaO6 octahedral tilts in the LaGaO3 perovskite structure were reduced by double doping with Sr and Mg. Reduction of the GaO6 octahedral tilt proved effective for oxide ion conduction.
Authors: Kunio Yamamoto, Kenji Sakai, Shinzo Yoshikado
Abstract: The purpose of this study is to prepare high-quality TiO2 thin films for dye-sensitized solar cells using the electrophoresis method. A high-quality TiO2 thin film has a thickness of approximately 10 μm and no crack on the surface. In this study, TiO2 thin films were deposited by changing the configuration of electrophoresis electrodes. When electrodes were set parallel to horizontal and ITO glass substrate was set in the upper electrode, an excellent TiO2 thin film of approximately 10 μm thickness was obtained by depositing very thin TiO2 films as a buffer layer. The new film has the highest open-circuit voltage and short-circuit current density.
Authors: Masato Sakata, Teiichi Kimura, Takashi Goto
Abstract: C-Ru-RuO2 nano-composite films were prepared by plasma-enhanced chemical vapor deposition and their microstructure and electrode properties were investigated. Ru-C nano-composite films consisted of Ru nano-particles of 3 nm in diameter and an amorphous C matrix. With increasing oxygen gas flow rate (FRO2), the volume fraction of C decreased from 0.91 to 0 and Ru nano-particle size increased from 2.5 to 4.5 nm. At high FRO2, the film consisted on the fibrous RuO2 and Ru-C nano-composite layer. Ru-C nano-composite containing 91 vol% C showed the highest interfacial electrical conductivity below 673 K, and Ru-C/RuO2 composite containing 0 – 5 vol% C showed the highest interfacial electrical conductivity at 873 K. Electro-motive-force (EMF) values of an oxygen concentration cell constructed from a YSZ electrolyte and Ru-C or Ru-C/RuO2 composite electrodes responded to the change of oxygen gas partial pressure at more than 473 K. The response time of the concentration cell with Ru-C nano-composite electrodes at 573 K was less than 10 s, and that with Ru-C/RuO2 composite electrodes was about 300 s.
Authors: Manickam Minakshi, Pritam Singh, Melody Carter
Abstract: The redox behavior and surface characterization of manganese dioxide (MnO2) containing titanium boride (TiB2) as a cathode and Zn as an anode have been investigated in aqueous saturated lithium hydroxide (LiOH) electrolyte battery. The electrode reaction of MnO2 with TiB2 in this aqueous electrolyte is shown to be lithium insertion rather than the usual protonation. The influence of TiB2 additive (1, 3 and 5 wt. %) on the performance of MnO2 as a cathode and its cycling ability have been determined.
Authors: Takashi Teranishi, Sachi Takezawa, Kenji Toda, Hironori Ishikawa, Kenji Sato, Kazuyoshi Uematsu, Mineo Sato
Abstract: Reduced niobates, MLixCa2Nb3O10 (M = Rb, K and Na) and KNaxCa2Nb3O10 were synthesized by intercalation reaction with n-butyllithium or sodium azide. Ruddlesden-Popper type structure of sodium intercalation compound, KNaCa2Nb3O10, differ from that of the parent compound and lithium intercalation compound, KLiCa2Nb3O10. The magnetic susceptibility measurements showed that the sodium intercalation compound became superconductor with transition temperatures below 3.5 K. New lithium intercalation compound Na0.1Li0.8Ca2.45Nb3O10, for an ion exchange compound, Na0.1Ca2.45Nb3O10, with KCa2Nb3O10 type structure show the diamagnetic signals below 5 K.
Authors: Yoshinobu Saito, Kenji Yokota, Kenji Yoshihara, Morihiro Saito, Jun Kuwano, Hidenobu Shiroishi
Abstract: The activity of electrochemical oxygen reduction (EOR) for the pyrochlores Ln2Ru2-XO7-δ (Ln=Pr,Nd,Sm) [LnR] were examined in 0.1 M KOH aqueous solution at 70oC. The onset voltage (Vo) of the oxygen reduction current and the efficiency (E4) of 4-electron reduction of oxygen were evaluated by semi-steady state voltammetry with rotating ring-disk electrodes. PrR with the highest EOR activity showed Vo = ~ 0.85 V vs. reversible hydrogen electrode and E4 values above 80 %. Their Vo and E4 values show that LnR containing Ln with a smaller atomic number has a higher EOR activity, i.e. the order of the activity is PrR > NdR > SmR. This was in good agreement with that of the lattice parameters of LnR. These results indicate that the EOR activity of LnR depends on the kind and/or the size of the lanthanide metal ion on the A-site. PrR and NdR exhibited higher E4 values than known excellent Pb2Ru2O7-δ electrocatalyst containing toxic Pb.

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