Fundamental studies of the formation of periodic structures in oxide glasses were reviewed. High spatial frequency gratings and two-dimensional sub-wavelength structures were fabricated using a combination of lithography and dry etching processes. An ultra-small demultiplexer was realized on a SiO₂ tip in which gratings, a pair of parabolic reflecting mirrors, and channel waveguides were integrated. Adopting a precisely regulated sub-wavelength structure achieved low reflectance of the SiO₂ surface. Ultraviolet laser induced structural change was useful for creating diffraction functionality. The formation of point defects with intense absorption was indispensable for inducing change of the positive refractive index of the glass. Thermally stabilized Bragg gratings and athermal waveguide filters were prepared using Ge-B-SiO₂ glass films that were irradiated with a KrF laser.

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Effective use of the interstices of inorganic host structures is the key to develop new functional materials. The interstices in layer structured crystals are most versatile; the reaction concerning the interlayer space is called intercalation. Some examples of new functional materials developed using interstices are briefly reviewed, such as clay-organic complexes, porous pillared materials, interlayer grafting, anion exchangeable compounds, and layer structured nitride superconductors. A new silicon clathrate superconductor with a Si-sp³ cage structure is also introduced.

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Reuse/recycling of silicate bonded silicon carbide plates materials after removal from ceramic industrial service was evaluated for ceramic and steel industry. Experimental batches from spent slabs with different contents of bauxite and silica fume were prepared and fired up to 1400°C. Their densification properties in terms of bulk density and apparent porosity were measured and correlated with objecting properties. Mineralogy and microstructure of the sintered batches were studied and correlated with the ratio of their cold crushing strengths after 30 subsequent thermal shock cycles and before subjecting the batches to the thermal shock. The formation of mullite, replacement of silicon carbide by mullite and formation of pseudo silicon carbide, tight structure and well distribution of silicon carbide were recorded. The ratio of strengths after and before shock enhanced with increasing mullite content up to about 40%. All batches gave a superior thermal shock resistance where no spalling was observed up to 30 cycles of heating up to 950°C and water quenching.

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Although a calcium hydroxide preparation is widely used in dental clinics as a base liner and a root canal filling material, its very high basicity causes necrosis of the dental pulp and it does not set. In this study, we evaluated the feasibility of developing a calcium hydroxide preparation that has a good setting ability and a moderate basicity. The calcium hydroxide preparation examined showed a good setting ability and formed an apatitic mineral upon setting when dicalcium phosphate anhydrous (DCPA) powder was added and mixed with sodium hydrogen phosphate aqueous solution. Setting mechanism had a close relationship with apatite formation. As a result of the addition of DCPA, that is, acidic calcium phosphate, the calcium hydroxide preparation showed a relatively mild basicity when compared with the DCPA-free calcium hydroxide preparation. An animal study demonstrated that a calcium hydroxide preparation containing DCPA causes less inflammatory response at the initial stage and elicits faster secondary dentin formation than DCPA-free calcium hydroxide preparation. We concluded therefore that a calcium hydroxide preparation containing DCPA is a promising alternative to the calcium hydroxide preparation currently used in dental clinics.

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The crystal structures of Ce₂Zr₂O₇ and β-Ce₂Zr₂O_7.5 were precisely determined by the Rietveld refinement of powder X-ray diffraction data. The present refinement revealed that the structure of β-Ce₂Zr₂O_7.5 was formed by filling a half of oxygen vacancies of Ce₂Zr₂O₇ in the specific ordered manner. The oxygen vacancy site is divided into two equivalent sites, one of which is completely occupied, when the composition becomes Ce₂Zr₂O_7.5. The formation of β-Ce₂Zr₂O_7.5 can be well explained on the basis of the argument that Zr⁴⁺ ions tend to be 7-fold coordination at low temperatures. The derived local atomic displacements associated with the oxygen absorption/release, particularly those of oxygen at the specific sites, could be a key issue to solve the reason why Ce₂Zr₂O_7+x exhibits the excellent property of oxygen release and absorption even at relatively lower temperatures.

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CeO₂-ZrO₂-MO_1.5 (M=La, Nd) powders to be used as three way catalysts for automotive exhaust gases were prepared from nitrate solutions by co-precipitation method. As a catalyst exposed to high temperature gas, a high thermal stability is required to keep high surface area. High oxygen storage capacity is also required. In this study, their oxygen storage capacity (OSC), surface area (SA) and temperature programmed reduction behavior (TPR) of CeO₂-ZrO₂-MO_1.5 powders were measured. The substitution of ZrO₂ by MO_1.5 increased the OSC value at calcination temperature 1000°C. SA values decreased as the calcination temperature increased, and SA was suppressed by the addition of MO_1.5. In both cases, the effect of LaO_1.5 addition was higher than that of NdO_1.5.

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A new approach is presented to prepare a rutile layer on titanium substrates. According to this approach, pulverized glass, composed of 3CaO•4B₂O₃•3TiO₂, is first developed on the substrate, heated up to 700 to 850°C, and then removed by soaking in hot water. During the heating process, rutile grew at the glass coating-substrate interface to form nano-sized crystallites. The rutile layer induced apatite formation within 3 d when soaked in simulated body fluid of the Kokubo recipe. Such in vitro bioactivity was attributed to many Ti-OH groups on the crystallite surface derived from hydrolysis of bonds at the crystallite-flux (matrix) interface like (rutile)-Ti-O-B or Ti-O-Ca-(the borate matrix).

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In order to obtain thinner Ni electrode layers for MLCCs, BaTiO₃ organometal resinate was added into Ni paste, which consisted of 0.2 μm or 0.4 μm Ni powders. Ni electrode films were fabricated with the Ni paste added with BaTiO₃ organometal resinate, and sintering and electrical characteristics of the film were examined in the present study. The experimental results indicated that addition of BaTiO₃ organometal resinate as small as 1 mass% remarkably suppressed the sintering of the Ni electrode films, i.e., no abnormal grain growth was observed on Ni electrode films with BaTiO₃ organometal resinate. In addition, MLCCs with 10-stacked layers was experimentally fabricated. The results indicate that the continuity of electrodes characteristics of the MLCCs are not impaired regardless of the size of the Ni particles. An addition of BaTiO₃ organometal resinate was found to be extremely effective for obtaining thin electrode layers.

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β-tricalcium phosphate (Ca₃(PO₄)₂, β-TCP) is known to be biocompatible and osteoconductive. In the present study, β-TCP ceramics were prepared by the spark plasma sintering (SPS) technique at temperatures ranging from 800 to 1000°C at a pressure of 60 MPa for 10 min at a heating rate of 25°C/min. No phases other than β-TCP were detected in the samples sintered at 800, 900 and 1000°C by X-ray diffractometry. The relative densities of the β-TCP ceramics sintered at 800, 900 and 1000°C were 70, 95 and more than 99%, respectively. Transparent β-TCP ceramics were obtained at 1000°C for 10 min. From the results obtained by scanning probe microscopy, the ceramics prepared at 800 and 900 °C were found to have a few pores. The transparent ceramics had an average grain size of 1.5 μm and seemed to be pore-free.

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A Si_0.8Ge_0.2 multilayered thermoelectric element with ten pairs of p-n layers was fabricated by simultaneous sintering and joining of Si-Ge powders with a sandwiched alumina cloth. Every p-n joint of the element was firmly connected without any cracks and the alumina layer inserted here remained unchanged even after a pulse-current sintering process. The maximum output, P_max, of this element was determined in the temperature range of 473-1273 K, and then increased in proportion to the second order of the temperature difference between the hot and cold ends of the element. As a result, P_max was 120 mW when the temperature difference was 500 K.

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