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The relationship between the chemical bonding of cation-oxygen bonds and microwave dielectric properties of Mg₄Nb₂O₉ compound and solid solutions was investigated in this study by using Rietveld analysis and molecular orbital calculation method. The results of molecular orbital calculation revealed that the covalency of cation-oxygen bond in NbO₈ octahedron increased by the Mn, Co, Ni and Zn substitutions for Mg, while that of cation-oxygen bond increased when Nb was substituted by Ta and Sb; the variations in the dielectric constant showed a similar tendency to those of covalency of cation-oxygen bonds in the MgO₈ and NbO₈ octahedra

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High quality of crystalline quartz as material of the dielectric-filled waveguide at millimeter-wave band is discussed. Then the dielectric waveguide resonator with quality factor exceeding 1,000 is achieved and applied to the filter at 60-GHz band by using crystalline quartz. The filter exhibits very low insertion loss of 1.5dB and below in the pass band of 1GHz. Moreover, a new antenna using the dielectric-filled waveguide is also developed.

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Currently, miniaturization and high frequency application are required to the electronic devices. At high frequency application, it is necessary to decrease equivalent series resistance (ESR) of multilayer ceramic capacitors (MLCs). It is efficient in decreasing ESR to using low dielectric constant material to make the number of lamination larger. We developed Mg₂SiO₄-SrTiO₃ ceramics, of which the dielectric constant is 9, and the temperature coefficient of capacitance (TCC) is NP0. Using this material for MLCs, dispersion of SrTiO₃ in Mg₂SiO₄ has great influence on insulation resistance. In this paper, we report the relation between dielectric properties and microstructure of Mg₂SiO₄-SrTiO₃ ceramics.

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BMT were prepared at some different sintering conditions and their dielectric properties were evaluated by microwave method. Also far infrared reflectivity of the BMT were measured and their lattice vibration frequencies and damping constants were calculated.

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A ferroelectric capacitor composed of Pb(Zr,Ti)O3 film is the main ferroelectric material used in FeRAM by many companies. FeRAM has many advantages over other non-volatile memories but basic understanding linking material properties in the capacitor and electrical properties has not been clarified. Controlling the film composition is key for preparing devices with high reliability. In this presentation results on sputtering of PZT films from ceramic targets containing excess Pb will be presented in order to clarify the sputtering mechanism and film composition impact on ferrelectric properties.

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RMnO₃ (R is rare earth) crystallizes in a hexagonal structure when the ionic radius of R is small (R=Ho-Lu, Y, Yb, Tm and Sc). In this hexagonal structure, each Mn3+ ion with S=2 is surrounded by three in-plane and two apical oxygen ions, and thus is subject to a trigonal crystal field. These MnO5 blocks are two-dimensionally connected with each other on their corners, and the triangular lattice of the Mn3+ ions is formed. Based on such a triangular lattice, these compounds experience several characteristic distortions. One is Mn trimers, which are characterized by the shift of three Mn3+ ions surrounding one oxygen ion toward the oxygen. Another one is the displacement of ions along the c axis (perpendicular to the triangular-lattice plane) causing a ferroelectric polarization. Since the ferroelectric transition temperature of these compounds is fairly high (>900 K), they have potential use for application, for example, ferroelectric gate FETs. Here, we show the dielectric anomalies at around Néel point of YMnO₃ epitaxial films deposited by pulsed laser deposition method. The relationship between the magnetic structure and the dielectric properties are discussed in terms of the temperature dependences of magnetization and dielectric permittivity. Eventually, the control of ferroelectric domain switching by applying external magnetic field is presented.

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Stable discharging of pure nitrogen can be maintained even at atmospheric pressure when alternative pulsed voltage is applied between two parallel plate electrodes. From optical emission spectroscopy, emissions from the N₂ 2nd positive and Herman's infrared systems were observed. Using this atmospheric pressure plasma, 1.8 nm-thick silicon nitride film was obtained at a temperature as low as 25ºC, and the thickness was regardless of the temperature. The thickness change against the pressure well corresponds to the change in emissions from the N₂ 2nd positive system. We conclude that excited species generated through N₂ 2nd positive system contribute to silicon nitridation and that it has extremely high reactivity. Furthermore, the leakage current density of the films was lower by one order of magnitude than those of previously reported silicon nitride films.

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The development of fine fluorescent materials with high and stable luminescence efficiency is demanded in order to achieve much higher brightness and finer resolution in innovation of a display. Phase separation glasses and glass-ceramics are candidates of new materials with high luminous efficiency because of the effects of a multiple light scattering due to phase separation texture and fine crystallization at the boundary of the two phases in the materials. In this study, Eu-doped phase separated glasses and glass-ceramics in CaO-Al2O3-SiO2 system were prepared. The effects of the composition, the heat-treatment condition for crystallization and the crystalline phases on the fluorescent characteristic were examined

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ZnO has a wide band gap of 3.37eV at room temperature and has attracted some interest because it is considered a promising green light-emitting phosphor for low-voltage luminescence in flat panel displays such as vacuum fluorescent tube (VFDs) and field emission displays (FEDs). It has been increasingly requested to develop blue cathode phosphors with high-efficiency and low-cost. The blue emission luminescence can be expected in Mg-doped ZnO because the band gap increases under partial substitution of MgO for ZnO. In the present work, the fabrication for (Zn,Mg) O solid solution and the effect of Mg-doping on the photoluminescence were investigated.

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The electronic structures of S-doped TiO2 with an optimized anatase structure were calculated within the framework of the density functional theory (DFT). Two type super-cells, type-A containing 12 atoms and type-B containing 48 atoms, were built for S-doped anatase by substituting an S atom for a Ti atom. The lattice constants obtained for the structure-optimized supercells were well agreement with a few percent of difference, compared with those of the structure-optimized anatase. The top of the valence band of anatase was approximately located near the X-point and the bottom of the conduction band at the -point. This means that TiO2 with anatase structure is an indirect-gap material. Although it is expected for the type-A that S-related energy states lying from -1.6 to 0 eV play an important role in the photocatalytic performance in the visible-light region, the stoichiometry is Ti1-xSxO2 with x = 0.25, not comparable to that estimated in the experiment (ca. 1.6 %). Therefore, a large super-cell named type-B was prepared by expanding anatase structure each 2 times in the direction of a- and b-axes. For the type-B, atomic-like S-related DOS occupied by electrons appeared in the band gap of anatase. The separation width between the S-related states and the valence band of anatase was estimated to be about 0.8 to 0.9 eV, which almost agrees with the amount of the absorption edge shift given in the literature.

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Glass beads incorporating semiconductor nanoparticles have attracted much attention due to their excellent long-term stability and potential applicability to many areas ranging from optoelectronics to biological labeling. Here we report the fabrication of a new-type highly photoluminescent glass beads dispersing CdTe nanoparticles by inverse micelle method. The nanoparticles (CdTe) prepared in aqueous solution were first mixed with tetraethyl orthosilicate (TEOS), then mixed with an organic solution containing a non-ionic surfactant that formed inverse micelle, and finally mixed with additional TEOS. The red-emitting glass beads thus prepared showed an emission efficiency of 65%.

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A novel and facile preparation method for layer-by-layer (LbL) self-assembled films incorporating nanocrystals (CdTe and ZnSe) is presented. Silane couple agents have been used as a linkage between nanocrystals layers. Dipping into a solution of surfactant (thioglycolic acid) enables to prepare transparent films. The multilayer glass film shows the same emission spectrum as in the solution with an efficiency more than 40% after refractive index correction. Since the concentration of the nanocrystals is very high (0.01 M), the glass can be used for various applications.

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Alkaline or alkaline earth metal borate glasses containing Eu or Sm cations were prepared and characterized their luminescence properties before and after crystallization by conventional thermal heating or laser irradiation. The crystallized glasses provided the unique luminescence properties derived from the reduced Eu or Sm ions (divalent ions). Also, the crystal dotts or lines were formed on the glassed containing Sm3+ ions.

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Spherical artificial graphite powders, so-called as mesocarbon microbead powders, were treated in Ar-H2-SF6 radio-frequency inductively coupled thermal plasma. Sulfur and fluorine incorporated into particles. An anode of lithium-ion rechargeable battery made from plasma-treated powder had a discharge capacity as much as 13% greater than that made from untreated powder, while its irreversible capacity loss (ICL) was as much as 9% less. More interestingly, the specific ICL calculated by dividing the ICL by surface area decreased as the surface area increased.

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