Although sub-nano quantum dots (QDs) are now becoming the most fascinating materials in nanotechnology, the accurate syntheses of QDs are generally difficult. Facile templating methods utilizing porous materials have a limitation due to an existence of the uncontrollable pore diameter range between 0.7 and 1.1 nm. In this study, the missing link has been entirely bridged with successful production of supermicroporous silicas (SMPSs) by using a solvent-free method. The finely tuned sub-nano pores of SMPSs act as an excellent template for the preparation of sub-nano QDs of transition metal oxides.

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

In this study, several metal particles were synthesized, Ni, Ag, and so on. The obtained products were evaluated by various methods such as X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and N2-adsorption measurements. The influence of several condition, temperature, synthesis time and molar ration of HCOOH / M were investigated.

View full abstract

LC and LE processing for Cu nanoparticles were developed by novel microwave liquid-solid reaction. We used metal oxide as metallic source and alcohol as solvent in this system. This system can be synthesized Cu nanoparticle in high concentration, a short time and non-waste, so low-pricing of Cu nanoparticle is realizable. By using acetic acid as dispersant, it can obtain single dispersed Cu nanoparticles suitable for printed electronics. In this study, fabricated conditions were examined in detail, reaction mechanisms and morphology of products were investigated and characterized sintering properties.

View full abstract

Local environment of trace elements in β-tricalcium phosphate has been investigated by the X-ray absorption near-edge structure (XANES) analysis with the aid of the first-principles calculations. Present analysis has successfully determined the local environment of doped Na, Mg, Mn and Zn ions in β-TCP.

View full abstract

The new Strontium Boron Silicon Aluminum nitride Sr₂Si_2+3xAl_2-xN_8+xB_2-2x(x⋍0.05) was synthesized under 1 MPa nitrogen atmosphere at 1800 °C. The crystal structure was determined using single-crystal X-ray diffraction method and SEM-EDS analysis. The crystal structure is characterized by the framework that consists of BN3 triangles and (Si,Al)N4 tetrahedra, and the disordered substructures on its 6-fold rotary inversion axes.

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

The activity on the Mg-C reaction of amorphous carbon black particles, crashed single crystalline graphite and graphitized carbon black particles have been evaluated in a transmission electron microscope by means of in-situ high temperature heating experiments. Active Mg-C reaction on a MgO single crystal with amorphous carbon and crashed graphite has been observed at around 1500ºC. However, apparent reaction has not been observed with graphitized carbon black particles up to the temperature at which MgO shows sublimation. Low activity of graphite c-plane on MgO-C reaction has been suggested.

View full abstract

The ability to resolve spatially and identify chemically atoms in defects is particularly important in polycrystalline materials, in which the grain boundaries have profound implications for the properties and applications of the final material. However, such atomic resolution is still extremely difficult to achieve, partly because grain boundaries are effective sinks for atomic defects and impurities. Here we show that the combination of advanced electron microscopy, spectroscopy and first-principles calculations can provide three-dimensional images of complex, multicomponent grain boundaries with both atomic resolution and chemical sensitivity. These results offer insights into interactions between defects and grain boundaries in ceramics and demonstrate atomic-scale analysis of complex multicomponent structures.

View full abstract

We report direct observation of fluorine ion dopants in the recently discovered LaFeAsO1-xFx superconductor, where the doping is critical for the superconductivity. Employing spectroscopic imaging based on scanning transmission electron microscopy, the spatial distribution of the doped fluorine ions, which are invisible in Z-contrast imaging, is clearly visualized with atomic-scale resolution. The observation directly proves that fluorine substitutes into the oxygen site in the superconducting LaFeAsO1-xFx compound. Our results demonstrate the potential of the present method for revealing dopants undetectable by conventional microscopy imaging.

View full abstract

Atomic structure of the domain and the domain boundary in the polycrystalline electrolyte Li0.34La0.51TiO3 have been systematically studied via combined advanced scanning transmission electron microscopy methods. 90-degree-oriented and antiphase domain boundaries were both found in this Li-rich compound. Meanwhile, abundant La-vacancies were observed to be randomly created among the A-sites in the La-poor layer and were found to have resulted in the evident Ti-displacements towards the La-poor layer. Formation of such domain boundaries and the La-vacancy, associated with their microstructure features as well as their contributions to the material's ionic conductivity are discussed.

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

This paper reports on the synthesis of Nd³⁺ doped nanosheets by exfoliation of layered perovskites, KLa_1-xNd_xNb₂O₇, K₂La_2-xNd_xTi₃O₁₀ . These nanosheets are applicapable in advanced bio-imagining proves and bio-sensors, owing to the molecular-scale thickness and luminescence in the near infrared region by the 808nm excitation.

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

Phosphors of (Ba, Sr)₂SiO₄:Eu²⁺ (4%) with emission colors ranging from green to orange, which depends on Ba/Sr ratios, were synthesized by our originally developed gel-assisted freeze drying method using a unique water-soluble silicon (WSS) compound as a silicon source in combination with a flux treatment. All the samples with compositions of Ba₂SiO₄:Eu²⁺, Ba_0.6Sr_1.4SiO₄:Eu²⁺, Ba_0.4Sr_1.6SiO₄:Eu²⁺ and Sr₂SiO₄:Eu²⁺ were efficiently excited with a blue light (450 nm) with the corresponding emission maxima at 512, 550, 563, 581and 615nm, and their emission intensities were 2.4, 1.7, 1.7 and 1.1 times larger than that of one of the commercially available YAG:Ce³⁺phosphor, respectively.

View full abstract

The authors have demonstrated the light emission of rare earth (RE)-free oxide glass containing Sn2+ emission center. The RE-free glass shows the light emission with a high value of quantum efficiency (QE) comparable to conventional crystalline phosphor. It is notable that the high QE value is attained for RE-free transparent glass and the broad emission can be continuously tuned by both the amount of activator and the composition of the glass. Since this glass possesses low-melting property, we emphasize that the glass phosphor will lead to the development of a novel inorganic white-light-emitting device in combination with a solid state UV light-emitting source.

View full abstract

[in Japanese]

View full abstract

Silicone resin micro particles in an averaged diameter of 2 micrometer were decarbonized in a controlled atmosphere in a temperature range of 650 - 900 C. Ceramization process in this temperature range was investigated in terms of mass loss, specific surface area and IR spectroscopy. PL spectra was observed by He-Cd laser excitation. Fomration of a PL center with a peak at 410 nm with unsymmetrical spectrum feature at the early stage of the decarbonization is indicated.

View full abstract

In this study, LiAlO2 doped ZnO particles were prepared using a solution technique. When adding to the solution of LiAlO2, the XRD pattern of the synthesized particles corresponded to ZnO after drying and heating at 1173 K. Since the diffraction peaks of LiAlO2 were not detected in the obtained ZnO particles, above 10 mass % of LiAlO2 seemed to be perfectly solved in ZnO. Farther, then the synthesized ZnO particles showed 1-3 micron in size.

View full abstract

[in Japanese]

View full abstract

--

View full abstract

Ethyl-modified polysilsesquioxane (PSQ) liquid has been synthesized by a cosolvent-free liquid-phase hydrolysis and polycondensation of ethyltrimethoxysilane-water binary system. Thermal curing of the PSQ liquid yields a monolithic ultraviolet (UV)-transparent PSQ glass. This organic-inorganic hybrid glass would be a new silica-based UV transparent material derived at relatively low temperature.

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

The formation of titania nanocrystalline coatings at low temperatures via sol-gel process with hot-water-treatment is reviewed. The effects of external fields on the formation of titanaia nanocrystals from the films are discussed. Promising characteristics of the resultant titania nanocrystals-dispersed coatings with unique are described.

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

We demonstrated the high aspect ratio microfabrication process of (001)TiO2 for photoniccrystal structure by SF6-RIE technique. Cr micro patterns as an etching mask material were prepared on a TiO2 single crystal (rutile) by photolithography and radio frequency (RF) sputtering. The TiO2 was anisotropically etched along [001] by optimizing the etching conditions. The higher selectivity etching rate ratio of TiO2/Cr was obtained by lower RF power and higher flow rate of SF6. In addition, higher anisotropic etching with a higher aspect ratio was achieved by higher RF power and high flow rate of SF6.

View full abstract

[in Japanese]

View full abstract

Li2Ge4O9 is known to be a ferroelectric phase with Curie temperature at Tc=-83 (degree)C. In this study, we found both low-frequency phonon and heat-capacity anomalies around 100(degree)C in the Li2Ge4O9 phase, demonstrating presence in a structural phase-transition. The phase transition is probably triggered by regularization of distorted GeO6 octahedra in the paraelectric phase, resulting a new phase consisting of the regular octahedral GeO6 unit, which was supported by in situ emission measurement in the Mn4+-doped phase. It is deduced that the phase transition is more dynamic than ferroelectric phase-transition originating in ordering of the Li ions.

View full abstract

Currently the types of garnet transparent ceramics have been under intense investigation for X-ray and gamma-ray detection. They were produced by the technique of sintering monocrystalline grains into a large inorganic ceramic. Transparent ceramics of Ce3+-doped Y3Al5O12 (YAG) and (Gd, Y)3Al5O12 (GdYAG) especially demonstrated the ability of highly light yield and fast response when exposed to ionizing radiation. In this study, we discussed Yb3+-doped YAG transparent ceramics with different concentration as a scintillation material. Charge transfer luminescence of the Yb3+ ion is attractive due to its ultrafast decay time of few to tens nanoseconds, depending on the host lattice and temperature. After checking optical transparency and absorption coefficient, we evaluated alpha-ray excited radioluminescence spectra, and determined the decay time using the streak camera system equipped with pulsed X-ray source. The relative light yield was measured by 241Am alpha-ray exposed pulse height spectra.

View full abstract

We discovered Yb3+ doped RE2O3 (RE:Rare earth) exhibits sub-ns ultra fast scintillation response based on the charge transfer transition of Yb3+. This is the first time that the charge transfer related scintillation is detected in room temperature. In the presentation, basic optiacal properties (transmittance and radio luminescence) and scintillation responses (light yield and scintillation decay time) will be presented.

View full abstract

Sintered pellets of 3 mol% yttria-stabilized zirconia (YSZ) were electrically polarized by applying dc voltages. The stored charges in the polarized pellets were confirmed using thermally stimulated depolarization current (TSDC) measurements. Each of the TSDC spectra has two peaks, located at lower and higher temperature. The lower and higher peaks are attributed to dipole polarization and space charge polarization, respectively.

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract