Miki Inada

Preparation of nanocrystalline ZnO/TiO2 film and its application to dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) were built by using ZnO/TiO2 films as electrodes consisting of ZnO nanorod arrays coated with TiO2 nanoparticles (NPs) in sol or slurry form prepared by sol–gel methods. The addition of TiO2 sol to ZnO arrays resulted in an improvement of cell performance, but the cell efficiency was not high. The cell efficiency was more improved by coating of ZnO arrays with TiO2 slurry. The tetraethylammonium hydroxide surfactant was effective to control TiO2 NPs suspension between sol and slurry. The penetration of TiO2 sol or slurry into ZnO array was important, especially in the long nanorod array. The cell performance of ZnO/TiO2 electrode increased more by TiO2 slurry than by TiO2 sol because TiO2 sol shrank more during calcination.

Fabrication of translucent silicon nitride ceramics with various sintering aids

Polycrystalline translucent Si3N4 sintered ceramics are receiving attention owing to their high mechanical strength and chemical stability. Regardless of a long history to sinter Si3N4, there have been few reports on the fabrication of translucent Si3N4 ceramics. In this study, the authors used three systems including AlN–MgO, AlN–Y2O3 and Al2O3–Y2O3 as sintering aids of Si3N4, and the phase composition and transmittance of sintered samples were compared. The translucent α–sialon formed at a large amount of sintering aids and the translucent β–Si3N4 formed at a small amount of sintering aids.

Dye sensitized solar cells based on ZnO nanorod/TiO2 nanoparticle composite films

ZnO nanorod/TiO2 nanoparticle composite films were prepared by a sol-gel method, in which the slurry of TiO2 nanoparticles (NPs) were penetrated into ZnO nanorod arrays. The agglomerate size of TiO2 NPs was controlled with tetraethylammonium hydroxide. Lowering ZnO nanorod array density was an effective way to fill TiO2 NPs in the space of ZnO nanorod array. The presence of ZnO and TiO2 was confirmed by scanning electron microscopy and X-ray diffraction. Triblock copolymer (P123) was added as a template agent to obtain high specific surface area, and the solar cell performance was improved. However, the viscosity of the TiO2 slurry was increased by addition of P123, and TiO2 content in the composite film was reduced. Low concentration TiO2 slurry was preferable to be penetrated into ZnO nanorod array and solar cell performance was further improved.

Effects of Sintering Conditions and Additives on Translucent Silicon Nitride Ceramics

Translucent β-Si3N4 sintered ceramics have been fabricated by using AlN-MgO sintering additives. In the present study, the authors employed AlN-MgO as a standard sintering aid, and investigated the effects of sintering conditions on the translucency of Si3N4. Furthermore, various oxides such as HfO2, Sm2O3, Y2O3, Sc2O3, La2O3, Nd2O3, CeO2, CaO, ZrO2 etc. were used as the sintering aids of Si3N4, and the sintered β-Si3N4 ceramics exhibited different transmittances in the visible region. It was found that the transmittance of sintered ceramics was mainly affected by the sintering additives.

Stabilization Mechanism of the Tetragonal Structure in a Hydrothermally Synthesized BaTiO3 Nanocrystal

Higher OH concentration is identified in tetragonal barium titanate (BaTiO3) nanorods synthesized by a hydrothermal method with a 10 vol % ethylene glycol solvent (Inada, M.; et al. Ceram. Int. 2015, 41, 5581-5587). This is apparently inconsistent with the known fact that higher OH concentration in the conventional hydrothermal synthesis makes pseudocubic BaTiO3 nanocrystals more stable than the tetragonal one. To understand where and how the introduced OH anions are located and behave in the nanocrystals, we applied ab initio analysis to several possible microscopic geometries of OH locations, confirming the relative stability of the tetragonal distortion over the pseudocubic one because of the preference of trans-type configurations of OH anions. We also performed Fourier transform infrared and X-ray diffraction analysis, all being consistent with the microscopic picture established by the ab initio geometrical optimizations.

Erratum:Synthesis of Magnetite Nanoparticles under Standing Ultrasonication

本誌第56巻第4号 p. 194に掲載の榎本尚也氏，山田浩介氏，党 鋒氏，稲田 幹氏，北條純一氏の研究論文，「マグネタイトナノ粒子の合成における定在波型音場効果」の受理日が誤っておりました．下記の通り訂正させていただきます．大変ご迷惑をお掛けしましたことをここにお詫び申し上げます．（誤）Received December 4, 2004 → （正）Received December 4, 2008