Composites consisting of Ce-TZP matrix and in-situ grown particles of barium hexaaluminate (BaAl₁₂O₁₉) as the second phase were prepared. To lower the sintering temperature and improve the microstructure of the composites, starting materials of two types of the second phase were used: mixed powders of BaCO₃ and α-Al₂O₃, and amorphous precursor powder. When the composites were prepared using the mixed powder of BaCO₃ and larger α-Al₂O₃ (3.0 µm) particles, aggregations of in-situ formed BaAl₁₂O₁₉ particles were observed in the Ce-TZP matrix. Although the formation temperature of BaAl₁₂O₁₉ decreased with decreasing average size of α-Al₂O₃ particles, full dense composites were unobtainable, even at the sintering temperature of 1400°C. To lower the formation temperature of the second phase further, amorphous precursor powder of BaAl₁₂O₁₉ was prepared using coprecipitation method. The composite prepared using the amorphous precursor powder was sufficiently densified at 1400°C. The BaAl₁₂O₁₉ particles formed in the composite were finer than those prepared using the mixed powder of BaCO₃ and α-Al₂O₃.

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We investigated the Na⁺ environment in sodium silicate glasses and mixed alkali silicate glasses using ²³Na multiple-quantum magic-angle spinning (MQMAS) NMR spectroscopy, ab initio molecular orbital (MO) calculations, and Na⁺ elution analysis. The ²³Na MQMAS NMR spectra of Na₂O–xSiO₂ and (1 − y)Na₂O–yM₂O–2SiO₂ (M = Li, K) glasses showed an inhomogeneous distribution of local structures around Na⁺, even though spectral deconvolution was impossible. The quantum chemical calculations indicated that the alkali silicate glasses contained both aggregated and isolated Na⁺ sites. The elution behavior also supported the local structure distribution described above. These results indicated that a cation with a high cation field strength tends to aggregate in mixed silicate glasses.

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The corrosion resistance of alumina-magnesia castable to a basic slag was evaluated to find the highly-resistive castable composition for steel processing. Stable solid phases were CA6, alumina and spinel after firing of the castable of Al₂O₃–MgO–CaO–SiO₂ system. The slag corrosion was simulated thermodynamically for CA6, alumina, spinel and castables. The solubility of each oxide component is expected in the order of MgAl₂O₄ > CA6 > Al₂O₃ at 1600°C because of the formation of CA2 on CA6 and the formation of CA2 and CA6 on alumina, suggesting the protection of castable from slag. However, CA2 and CA6 disappear at 1800°C and the solubility changes in the order of CA6 > Al₂O₃ > MgAl₂O₄. Although the protection of castable by CA6 is also expected, the CA6 disappears at a large amount of slag and a high temperature. The solubility of castable decreases with increasing MgO/CaO ratio owing to spinel formation. The practical immersion test demonstrated the high corrosion resistance of high MgO/CaO castable against slag, exhibiting the importance of spinel formation.

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In the present study, the effects of reflector bias voltage on the physical and chemical properties of nanocrystalline silicon deposited by reactive particle beam assisted chemical vapor deposition were systematically studied using various reflector bias voltages. During deposition, the substrate temperature was kept at room temperature. Nanocrystalline Si embedded in an amorphous matrix structure was analyzed by X-ray diffraction and Raman spectroscopy. Films that were deposited under high reflector voltage formed large grains due to largely accumulated internal energy. Using X-ray photoelectron spectroscopy, the chemical state of nanocrystalline silicon was revealed to have only metallic Si bonds. Further, an increase in reflector voltage induced a roughened surface morphology, an increased dark conductivity, and a decreased optical band gap in Si films.

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The conductance changes of an SmFeO₃ based p-type gas sensor due to the contamination level of air with ozone were examined. The conductance was responsive to sub-ppm levels of ozone. The dynamic range of the sensor to distinguish the air quality due to ozone contamination covered four levels, i.e., very good, good, poor and very poor.

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The influence of La₂O₃ addition on the thermal diffusivity and thermal conductivity of ZrO₂ ceramics has been investigated. Porous and dense ZrO₂ ceramics were fabricated by spark plasma sintering at 1100 and 1500°C. The porosity of ZrO₂ ceramics sintered at 1100°C increased with increasing 0–5 mol % La₂O₃ addition. In contrast, ZrO₂ ceramics sintered at 1500°C showed full density regardless of the amount of La₂O₃ addition. The La₂Zr₂O₇ of crystalline pyrochlore phase was formed by reaction between La₂O₃ and ZrO₂. The XRD peak of the La₂Zr₂O₇ phase increased with increasing La₂O₃ addition. The thermal diffusivity and thermal conductivity of sintered ZrO₂ decreased with increasing La₂O₃ addition. In addition, the thermal conductivity of the present samples decreased remarkably with increasing the porosity.

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α-LiFeO₂ columnar particles were synthesized by heating a mixture of γ-Fe₂O₃ and LiNO₃ at 500°C in air. CeO₂ nanoparticles were prepared from Ce(OH)₃ obtained by a precipitation method. The α-LiFeO₂ columnar particles were mixed with the CeO₂ nanoparticles in an aqueous solution and then the mixture of α-LiFeO₂ and CeO₂ was heated at 300°C to prepare the α-LiFeO₂ coated with CeO₂ nanoparticles. Then the effect of CeO₂ coating on CO₂ absorption ability of α-LiFeO₂ was investigated. As a result, coating of CeO₂ on α-LiFeO₂ particles was found to suppress the structural phase transition of α-LiFeO₂ to β′-LiFeO₂, although the synthesized α-LiFeO₂ underwent a structural phase transition of α-LiFeO₂ to β′-LiFeO₂ accompanied by the reaction of α-LiFeO₂ with CO₂ in the temperature range of 350 to 425°C. The suppression of the structural phase transition resulted in an increase in CO₂ absorption rate of LiFeO₂ in the temperature range up to 425°C. Thermodynamic analysis revealed that the α-LiFeO₂ phase has a lower activation energy for CO₂ diffusion than the β′-LiFeO₂ phase, which results in the enhancement of the CO₂ absorption rate of LiFeO₂.

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We report using high repetition rate near-infrared femtoseond laser to reduce Eu³⁺ into Eu²⁺ inside oxyfluoride glass. SrF₂ crystal was space-selectively precipitated with the irradiation of femtosecond laser and we successfully realized the reduction of Eu ions, confirmed with the observation of blue emission of Eu²⁺ at laser irradiated spots. The mechanism of the reduction is different from those in previous work which is based on the active electron and holes created by the infrared laser pulse. This work could extend selection of host composition of Eu-doped glass for 3D optical information storage.

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The microstructure and conditions for the formation of the reddish color referred to as hi-iro on Japanese ceramics were investigated through model experiments. The hi-iro marking was found to be formed by the reaction between clay and alkali ions supplied from the glaze. When a mixture of porcelain clay and 20 wt % KCl was heated in air at 1250°C and then cooled slowly to 800°C, hi-iro clearly appeared on the sample surface. In hi-iro, corundum [α-(Al,Fe)₂O₃], hematite (α-Fe₂O₃) and a liquid phase are formed. Upon heating until 1250°C, corundum is firstly precipitated as hexagonal plate-like crystals. During the cooling process, hematite precipitates on the edges of the corundum crystals to form specific composite particles. When rapidly cooled from 1250°C to room temperature, a brownish red color appeared on the sample surface, which was found to be caused by the formation of approximately 50 µm Al-substituted hematite (Fe_1.9Al_0.1O₃) particles. The relationship between the microstructure of the phases formed and the color is discussed.

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Coexistence of carbonate ions in aqueous solution often leads to difficulty in the preparation of stoichiometric hydroxyapatite (HAp), owing to formation of carbonate-containing HAp with low crystallinity. This study is focused on examining appropriate conditions to prepare HAp with reduced incorporation of carbonate through a wet processing in aqueous solution, starting from calcium chloride (CaCl₂) and trisodium phosphate (Na₃PO₄). Titration of Na₃PO₄ solution to CaCl₂ solution resulted in formation of crystalline HAp with low contents of carbonate, whereas titration of CaCl₂ solution to Na₃PO₄ solution resulted in formation of amorphous calcium phosphate that contains approximately 3 mass % of carbonate. The HAp particles prepared in a condition under coexistence of trehalose were finer and well-dispersed than those prepared in a solution free from trehalose. The addition of the Na₃PO₄ solution to the CaCl₂ solution contributes to nucleation of HAp with minimal carbonate incorporation.

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Size-controlled Pb-based glass frits ranged from 0.48 to 1 µm prepared by spray pyrolysis are used as an inorganic binder for Al electrodes. The Al electrodes formed from the pastes with the glass frits above 0.76 µm have uniform distribution of glass material inside and on the surface of the electrodes. Pb-based glass frits improve the formation of Al–Si alloys by liquid phase sintering. The Al electrodes have well developed back-surface field layers and low specific resistances irrespective of the mean sizes of the glass frits. The specific resistances of the electrodes change from 28.4 to 38.6 µΩ·cm according to the mean sizes of the glass frits at a heat-up rate of 800°C. The specific resistances of the electrodes are slightly affected by the heat-up rates.

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Effect of rare earths (RE) in the rare earth copper oxides, RE₂CuO₄ (RE = La, Pr, Nd, Sm, Gd) and RE₂Cu₂O₅ (RE = Dy, Ho, Er, Yb, Y), on the carbon oxidation was investigated by the DSC (differential scanning calorimetry) measurement. Orthorhombic La₂CuO₄ and tetragonal RE₂CuO₄ (RE = Pr–Sm) prepared at 800°C showed higher carbon oxidation activity compared with CuO processed at the same temperature, whereas activity of the orthorhombic RE₂Cu₂O₅ (RE = Dy–Yb, Y) prepared at 1000°C was lower than that of CuO processed at the same temperature.

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Submicron-size SiC ceramics were sintered to densities >97% of the theoretical density by adding 5 wt % in situ-synthesized nano-size SiC and 2 wt % AlN–RE₂O₃ (RE = Y, Er). The SiC ceramics showed very low electrical resistivity in an order of 10⁻⁴ Ω·m. This low electrical resistivity was attributed to the smaller amount (2 wt %) of sintering additives addition and their microstructural characteristics, i.e., growth of nitrogn-doped SiC grains and the confinment of non-conducting Y- and Er-containing phases in the junction areas.

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By using melamine as a nitridizing reagent, aluminum nitride (AlN) powders were prepared from δ- and α-alumina (Al₂O₃) powders which had not been mixed with carbon. The hydrogen cyanide (HCN) formed by thermal decomposition of melamine was involved in the nitridation of Al₂O₃ to AlN. The nitridation process of alumina to AlN was monitored by powder X-ray diffraction patterns and ²⁷Al magic-angle spinning nuclear magnetic resonance spectroscopy. δ-Al₂O₃ began to be converted to AlN at 1050°C without δ-α alumina transformation. The nitridation rate of δ-Al₂O₃ was much higher than that of α-Al₂O₃.

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