Photon emission (phE) often accompanies fracture of ceramics. The author has studied the phE for engineering ceramics and glasses to clarify its emission mechanisms. This paper reviews the recent studies to describe several factors contributing to the phE and to discuss phE mechanisms. Recently, it has been found that the phE is affected by surrounding gas, bending strength and fracture mode. The phE intensity depends on both of kind and pressure of surrounding gas. The dependence demonstrates that discharge of the gas is one of the origins of the phE. The positive correlation between bending strength and the phE intensity is observed for glass and single crystal ceramics, showing that the phE is associated with released energy by fracture. In polycrystalline ceramics, the phE intensity does not depend clearly on bending strength but on the proportion of transgranular fracture. This indicates that grain boundary has a large effect on the phE.

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Preparation of a dense Sc₂O₃-doped ZrO₂ (ScSZ) thin film electrolyte on a microtubular cathode support was accomplished using wet coating process and subsequent co-sintering. The microtubular (La,Sr)MnO₃ (LSM) cathode support had a 1.6 mm diameter and approximately 30% open porosity. The cell, with 20 μm thick ScSZ electrolyte, was electrochemically evaluated in a humidified (3% H₂O) hydrogen atmosphere. The microtubular cells exhibited a stable open circuit voltage above 1.05 V in the temperature range from 550 to 750°C. Maximum power densities of 46.5, 163.2 and 452.8 mW/cm² were generated at 550, 650 and 750°C, respectively. The results indicate that this preparation of a thin film ScSZ electrolyte effectively realized a stable, high performance LSM-supported micro SOFC.

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Second harmonic generation (SHG) and propagation loss have been measured on nanocrystallized optical fibers of tellurite-based glass, 15K₂O·15Nb₂O₅·70TeO₂. The result of the angular dependence of the SHG intensity is discussed based on the difference in the transmission factor varying with the polarization direction. Propagation-loss measurements on the fiber samples by a cut-back method showed low loss compared with that of a typical LiNbO₃ waveguide.

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Novel zeolite/tobermorite composites were prepared by hydrothermal treatment of a powder-compact consisting of mordenite and slaked lime. Tobermorite formed after the hydrothermal process due to the reaction of mordenite and slaked lime. The bending strength after the hydrothermal process was more than 7 MPa. X-ray diffraction analysis results showed that mordenite remained after the hydrothermal treatment, resulting in the existence of inherent micropores of mordenite in the composites. The composites exhibited a broad mesopore size distribution of more than 6 nm. The improvement in strength, mesopore formation, and specific surface area of the composites depended on the amount and size of the tobermorite that was formed.

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Fibrous Al₂O₃-(monoclinic-ZrO₂)/HAp-(tetragonal-ZrO₂) composites were fabricated with a core/shell microstructure by the multi-pass extrusion process depending on the volume fraction of Al₂O₃-(m-ZrO₂) core and HAp-(t-ZrO₂) shell. In the sample sintered at 1200°C, the Al₂O₃-(m-ZrO₂) core was composed of porous, equiaxed grains, independent of core/shell volume fraction. However, after sintering at 1500°C, the core phase was changed with elongated grains of a reaction phase CaAl₁₂O₁₉. Formation of elongated grain increased as the core diameter decreased. A significantly improved value of fracture toughness (4.3 MPa·m^1/2) was obtained in the Al₂O₃-(m-ZrO₂)/HAp-(t-ZrO₂) composites with 50_core/50_shell composition sintered at 1500°C.

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Effect of zirconia particle size on the nitridation behavior of silicon powder was studied in order to assess the influence of the zirconia particle size on the nitridation of silicon powder. Thermo-gravimetric analysis revealed that for samples held at higher temperatures the addition of zirconia powder resulted in a reduction of the temperature for the onset of nitridation of the silicon powder, and the degree of silicon to silicon nitride conversion at a given temperature was higher for samples nitrided with finer particle size of zirconia. For lower temperature, the degree of nitridation was studied as a function of holding time and samples with finer additions showed a much higher initial nitridation rate than those with coarser additions.

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To demonstrate availability of gamma distribution as the initial distribution of flaw size, three kinds of initial flaw size data of alumina ceramics were employed. Compared with a power function, gamma distribution was better fit to the data in every case. For practical use, an approximate expression of the initial distribution of flaw size was proposed by taking out a major part of the gamma distribution relating to the shape parameter. Finally, a positive correlation between the average fracture strength of the alumina ceramics and the shape parameter of the gamma distribution was discussed.

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(Mg,Ni)O solid solutions were synthesized by calcination of MgO and NiO mixtures (MgO:NiO = 65:35 in mol) at 1500°C for 2 h in air. When the samples were firstly reduced at 1000°C in a gas mixture of 4 vol% hydrogen and nitrogen, a volume expansion was observed. The results of powder X-ray diffraction (XRD) and scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDX) analyses suggested that the expansion after reduction was possibly caused by the creation of space between (Mg,Ni)O grains by segregation of nickel particles on (Mg,Ni)O grains. When the reduced samples were re-oxidized at 1000°C in air and then reduced again at 1000°C in a gas mixture of 4 vol% hydrogen and nitrogen, the samples revealed an accelerated expansion, which was much larger than that of the samples reduced once. The morphological characteristics of (Mg,Ni)O grains and segregated nickel particles of the samples those were reduced twice differed to those of the samples reduced once: however, the phases of the all samples were similar, as verified by XRD and SEM analyses. The accelerated expansion after re-oxidation and reduction might be related to changes in the microstructure of the (Mg,Ni)O grains with the nickel particles segregated.

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Novel dense and porous SiC-Si₃N₄/AlN composites were fabricated using a multi-pass extrusion process. In the 2nd and 3rd pass dense composites, the diameter of AlN fibers in the SiC-Si₃N₄ matrix was about 170 μm and 30 μm, respectively. The AlN fibers were refined in the SiC-Si₃N₄ composites with the increase of extrusion pass number. However, in the porous SiC-Si₃N₄/AlN composites, the thin layer of AlN was well coated on the continuous pore surface of the porous SiC-Si₃N₄ matrix. The thickness of the AlN layers in the porous composite was about 40 μm. The detailed microstructures and material properties of the dense and porous SiC-Si₃N₄/AlN composites were investigated using OM, SEM, XRD, TEM and HRTEM techniques.

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The reactivity of a newly developed oxygen ionic conductor, Nd_9.83(SiO₄)_4.5(AlO₄)_1.5O₂, with alkali carbonates was examined in air and CO₂. The reactivity of the developed ionic conductor was substantially lower than that of ZrO₂, 3YSZ and 8YSZ in air and also in CO₂. It is concluded that this newly developed oxide is more tolerant to the alkali contamination and is applicable as a potentiometric oxygen concentration gas sensor.

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Zn-Al layered double hydroxide containing benzenesulfonate was successfully synthesized by the hydrothermal reactions of aqueous suspension of zinc oxide and aluminum hydroxide in the presence of benzene sulfonic acid. The products were characterized by the sharp X-ray diffraction profile and platy particle morphology. The present very simple (hydrothermal reaction of the aqueous mixture) synthesis is applicable to a series of layered double hydroxides with different compositions and structures.

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Silver ions were incorporated into a soda-lime silicate glass substrate by applying 3 M AgNO₃-0.1 M polyethylene glycol (PEG) mixed aqueous solution on the glass and heating it at 300°C for 12 h. The glass substrate was colorless after the heat-treatment although the refractive index at the glass surface increased by 0.04. The glass was colored red-brown by the further heat-treatment at 550°C. The energy dispersive X-ray microanalyzer revealed that the silver migrated to around 20 μm in depth. These facts indicate that the AgNO₃ solution works as a "stain". Since the viscosity of the AgNO₃-PEG solution was less than 2 mPa·s, it could be deposited on a glass substrate by the inkjet technique. Dot arrays were formed on the glass substrate by the inkjet deposition. The dots had around 100 μm-diameter kept clear circles and aligned with a hundreds-micrometer frequency. The silver ions were incorporated into the dot areas of the glass surface by the heat-treatment. Then, we demonstrated that a micro-ordered periodical modification in the glass composition was easily formed by the staining using the AgNO₃ aqueous solution combined with the inkjet technique.

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Turbostratic boron nitride (t-BN) powder prepared by mechanical grinding of hexagonal boron nitride (h-BN) under the nitrogen atmosphere with the oxygen concentration less than 1 ppm was consolidated by spark plasma sintering (SPS). The turbostratic structure was maintained after the consolidation, which was characterized by XRD, Raman and IR spectra. The t-BN consolidated without any additives at 1900°C for 10 min under applied pressure of 100 MPa showed a bulk density of 95%. The bending strength, Young's modulus and Shore hardness of the consolidated t-BN were 72 MPa, 259 GPa and 117 Hs, respectively. They were much higher than those of conventionally consolidated h-BN. On the other hand, the thermal conductivity was 3 W/mK and much lower than the compact of h-BN.

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Beta-SiC/SiO₂ core-shell nanowires were obtained in a mullite boat after the reaction between silicon nanopowder and CH₄ gas at 1623 K (1350°C), without adding metal catalysts from outside. The as-grown nanowires were characterized by X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, scanning TEM, and infrared-ray spectroscopy. The results showed that the typical nanowires consisted of single crystalline β-phase SiC core of 50-70 nm in diameter and a uniform wrapping layer of low crystallinity SiO₂ of ∼15 nm in thickness, and their lengths were up to several tens of micrometers. The nanowires axes lay along the [111] direction of β-SiC. Oxygen from the experimental setup or the raw powder should be a key factor to synthesize the core/shell nanowires.

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A spray-drying process was applied to the mass-production of mesoporous silica particles. The applied nozzle pressure and amount of solvent in the precursor solution were varied to control the average particle size. The particle-size distribution showed a bell curve with a normal distribution. As the nozzle pressure was increased from 0.05 to 0.20 MPa, the average particle size was decreased proportionally. In addition, as the surfactant concentrations in the precursor solutions were decreased, the average particle size was decreased. Based on the results of low-angle X-ray diffraction measurements, N₂ adsorption measurements, and TEM observations, it was proven that well-ordered mesoporous structures were formed inside the particles. It is proved that the spray-drying conditions do not affect the mesoporous structures but do affect the average particle size.

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In a spray pyrolysis deposition (SPD) technique, deposition of film material and formation of surface structure are simultaneously occur, therefore, it is suitable for the preparation of microstructure-controlled thin films. We have modified the SPD technique to obtain a TiO₂ porous film and the films obtained were evaluated as a photocatalyst. The modified SPD technique consists of consecutive three steps to form nano-porous film. Initially, a mixture of colloidal TiO₂ of 40 nm in particle size and Ti-alkoxide dispersed and dissolved, respectively, in propanol was sprayed intermittently onto the heated glass substrate over 70 °C, 10 times. Secondly, the same colloidal TiO₂ dispersed into water was sprayed similarly onto the above film over 150°C. Finally, this two-times coated TiO₂ film was annealed at 500°C for 1 h. Five repetitions of this process gave the porous film with a thickness of 2.5 μm, led to the formation of neck at every contact-point between TiO₂ particles. The effective surface area of the film as a catalyst was 8 times larger than that of the non-porous TiO₂ film. Photocatalytic property of the film was evaluated by the decomposition of both aqueous coloring matter and gaseous odorant components under UV irradiation. For example, the reaction coefficients were enhanced from 0.02 min^-1 of the non-porous film up to 0.05 min^-1 for methylene blue and from 0.05 min^-1 up to 0.14 min^-1 for dimethyl sulfide. Consequently, the TiO₂ porous films prepared by the modified SPD technique have great potential as a useful photocatalyst.

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Morphotropic phase boundary in (1-x)Bi(Sc_0.5In_0.5)O₃-xPbTiO₃ (x = 0.45-0.50) piezoelectric ceramics was investigated in this study. The X-ray diffraction (XRD) analysis showed that a morphotropic phase boundary (MPB) with the coexistence of the rhombohedral tetragonal was in the vicinity of x = 0.47. In addition, the ferro-piezoelectric properties of this system were also investigated. Through electrical measurement, the composition at x = 0.47 close to MPB exhibited excellent piezoelectric properties with T_c = 394°C, d₃₃ = 324 pC/N, K_p = 0.51, and P_r = 23.6 μC/cm² and E_c = 2.08 kV/mm, indicative of a future device application.

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The hydroxyl-concentration distributions near the binding interface formed by heating contacted flat surfaces of various kinds of silica glasses at 1150°C were measured. The hydroxyl contents near the binding interface formed by the silica glass plates containing 1150 wt. ppm OH decreased, while those of the OH-free silica increased. As for a silica glass with ≈ 200 wt. ppm OH, the change in the hydroxyl content near the binding interface was within the variation of the hydroxyl content, ±≈ 20 wt. ppm.

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A new perovskite-type oxide, Ba_0.96Bi_0.86O_2.59(OH)_0.41 was prepared by low temperature hydrothermal reaction using NaBiO₃·nH₂O and Ba(OH)₂·8H₂O as starting materials. The crystal structure of this compound was refined by single crystal X-ray diffraction data, and the structure refinement with the space group Pm3m (#221) led to R_w = 0.035 and R = 0.054 for all reflections. This compound had the perovskite-type structure with the cubic cell of a = 4.2995(5) Å. The magnetic susceptibility of this compound exhibited no superconductive behavior down to 4 K.

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Bismuth layer structured ferroelectric ceramics, Sr_0.3Ba_0.7Bi_3.7La_0.3Ti₄O₁₅ (abbreviated as SBBLT), were fabricated by conventional and two-step sintering techniques. The effects of sintering processes on microstructure and dielectric properties of Sr_0.3Ba_0.7Bi_3.7La_0.3Ti₄O₁₅ ceramics were investigated. Dense and homogeneous ceramic materials with grain size of 1-3 μm were obtained. The decrease of oxygen vacancies in the two-step sintered ceramics decreases the conductivity, and also dielectric constant and dielectric loss at high temperature. The Curie temperature is shifted from 408°C of conventionally sintered ceramics to 345°C of two-step sintered ceramics at a soaking time of 15 h, which might attributed to smaller "rattling space" resulting from the decrease of unit-cell volume. The conductivity at high temperature decreases with increasing soaking time. The decrease in the conductivity is about one order of magnitude in two-step sintered samples.

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