Lithium niobate(LiNbO₃) and potassium lithium niobate(K₃Li₂Nb₅O₁₅) films can be prepared using environmentally-friendly aqueous precursor solutions. The process is reviewed by focusing on chemical properties and structure of a water soluble Li-Nb precursor molecule. The Li-Nb precursor molecule appears to be an oligomer having -O-Nb-O-Li-O- bonds with [NbO₃(OH)₃]^4- octahedral structure. The water solubility of the oligomer molecule may be due to the hydroxy groups surrounding the molecule, which makes the solution alkaline. This alkaline solution can be neutralized by acetic acid. High quality LiNbO₃ and K₃Li₂Nb₅O₁₅ films crystallize by heat-treatment at low temperatures. The low crystallization temperature of the LiNbO₃ film can be achieved because the precursor film contains no carbon residues, and the precursor molecule is designed to have the skeletal structure in the LiNbO₃ crystal. Micro-patterning of LiNbO₃ films are conducted by means of a coating process using neutralized aqueous precursor solution in the photolithographic technique. Aqueous precursor solutions with controlled composition can lead to the development of the processing of high quality powders and films in lead-free piezoelectric (K, Na, Li)NbO₃ ceramics and LiNbO₃ waveguides.

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A water-soluble tetraperoxo niobate [Nb(O₂)₄]^3- was prepared by reaction of niobic acid with H₂O₂ at pH=11 in aqueous ammonia solution. The corresponding ammonium salt, (NH₄)₃[Nb(O₂)₄], was grown as a single crystal, and its crystal structure was solved. A white precipitate has been obtained from the solution containing (NH₄)₃[Nb(O₂)₄] and Na₂CO₃. Based on the elemental, TG, redox titration and Raman spectroscopic analyses, we have concluded that the obtained compound was Na[Nb(O₂)₃]•2H₂O. This compound has been demonstrated to be a convenient precursor for synthesis of NaNbO₃ by simple calcinations in air at the reduced temperature of 400-500°C.

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We produced a nano TiO₂ coating on SnO₂: F (FTO) electrodes in an aqueous solution. Anatase TiO₂ crystallized in the transparent solution at 50°C for 10 min. The FTO electrodes with markedly uneven surface were successfully covered by nano TiO₂ without annealing. The TiO₂ was deposited on the electrodes with no clearance, thus attaining high adhesion strength. The coating showed high transparency, over 75%, in visible-light regions of 400 to 800 nm, which is similar to bare FTO electrodes. The electrodes had a unique surface structure resulting from the combination of uneven FTO surface and microasperity due to the nano TiO₂ coating.

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The cathodic electrodeposition of titania thin films from solutions containing a titanium salt was studied. Titanium tetrachloride was dissolved in an ethanol-water solution with hydrogen peroxide to prepare titanium peroxocomplex solutions. The deposition of the titania precursor on platinum-coated silicon wafer substrates was carried out by electrolysis of the solutions under constant current conditions. The deposits were thermally treated at fixed temperatures in air and then characterized by X-ray diffraction and scanning electron microscopy.

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Nanoscale particles of rutile- and anatase-type titanium dioxides were selectively grown in acidic solutions of titanyl sulfate. The variation of photocatalytic activity as a function of UV light intensity was investigated using rutile and anatase powders having almost the same size (20-30 nm) and shape for a clear comparison of the performance depending on the crystal structure. Whereas the performance of anatase evaluated with the decomposition of methylene blue and the reduction of Cr(VI) under UV light was proportional to the square root of the UV light intensity, rutile showed a saturation of the activity in the high-intensity region regardless of the light sources and photochemical reactions. The saturating tendency of rutile weakened with an electron-withdrawing reaction or a decrease in the grain size. Then, the performance of rutile could be superior to that of anatase under illumination at a low-light-intensity. The difference in the photocatalytic performance between rutile and anatase is tentatively ascribed to a high recombination rate of generated electrons and holes associated with a low mobility of carriers in rutile.

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Nanoparticles of brookite titanium oxide were prepared by microwave-assisted hydrothermal (MH) method at 200°C (heating time 5 min) for 0-60 minutes starting from the titanium peroxo glycolate complex in basic solution. The effect of microwave heating on the morphology of the brookite particles was examined. The samples were characterized by X-ray diffraction (XRD), Raman spectroscopy and transmission electron microscopy (TEM). It was found that all powders were composed of single phase brookite and contained two different types of particles. The activity in photodecomposition of oxalic acid by the samples prepared using MH method was higher than activities of brookite nanoparticles synthesized by the conventional hydrothermal method.

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TiO₂ particles were obtained from aqueous solutions by the liquid phase deposition (LPD) method. The crystalline anatase TiO₂ particles could be prepared below 100°C directly from aqueous solutions. The growth behavior of TiO₂ particles via the LPD process was investigated by dynamic light scattering (DLS) measurement and transmission electron microscopy (TEM). From DLS measurement, the particle growth process shows a sigmoidal curve and can be divided into three stages, i.e., the initial stage, the acceleration stage, and the completion stage. TEM measurements revealed that the primary particles with a diameter of ca. 50 nm were deposited at the initial stage. At the acceleration stage, these primary particles were assembled to form raspberry-like particles with a diameter of ca. 300 nm. Finally, the particles were precipitated by further aggregation with the micro-meter size at the completion stage.

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Single phase rutile was synthesized by a simple hydrothermal treatment of an aqueous titanium glycolate complex solution at 200°C for 24 h. The obtained sample was composed of 50×150 nm rod-like nanoparticles. The aspect ratio of the prepared particles could be controlled by adding glycolic acid or lactic acid to reaction solution. Up to 30×2000 nm whisker-like particles could be obtained. The hydroxycarboxylic acids favor development of specific crystal facets and allow to control the aspect ratio of the rutile nanoparticles. We also proposed a model, which explains formation of anatase and rutile, and disappearance of anatase particles during rutile crystals development.

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The titania particles were prepared by aging the mixture of titanium isopropoxide (TIP) and H₂O at 318 K. The anatase titania particles were obtained by the aging procedure at 318 K for more than 16 h. The aging temperature was quite low to obtain anatase-type titania particles. According to the DTA measurement, the amount of amorphous phase included in the titania particles decreased with increases in the aging time. Furthermore, the titania particles obtained by aging the mixture of TIP and H₂O at 318 K for 24 h contained no amorphous phase. The obtained titania particles had a high BET specific surface area of more than 250 m²/g. To characterize the titania surface, the adsorption isotherms of the organic dye molecules in an aqueous solution were measured. The negatively charged Evans blue molecules strongly adsorbed on the titania surface obtained by the low-temperature hydrolysis reaction as compared with the results of the methylene blue molecules. Furthermore, the decomposition kinetics of the dye molecules by the photocatalytic activity also deepened with the charge of the dye molecules. The relation between the UV irradiation time and the molar ratio of the decomposed dye molecules followed the Avrami equation. According to the results of the analysis using the Avrami equation, the Evans blue molecules were decomposed on the titania particle surface. In contrast, the methylene blue molecules were decomposed in the aqueous solution. The difference in kinetics was related to the interaction of the dye molecules and the titania surface. The high surface area of the titania particles obtained the low-temperature hydrolysis reaction of titanium alkoxides enhanced the effect of the surface interaction on kinetics of the photocatalytic activity.

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Titanate aqueous solution (TIP-Lac) prepared by direct reaction of titanium tetraisopropoxide (TIP) with lactic acid (Lac) in water shows characteristics of a polyanion and acts as a dispersant for preparing aluminum oxide suspension. When small amounts of TIP-Lac were added to aqueous dispersions of alumina, which had a positive surface charge at pH 4, agglomeration of alumina occurred, and alumina was redispersed by further addition of TIP-Lac. The fluidity and dispersion of alumina were studied from the zeta potential, sedimentation velocity, and rheological measurements.

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ZnO films were electrolessly deposited in the aqueous solution of zinc nitrate and dimethylamine-borane (DMAB). ZnO was deposited on the Pd catalyst layer grown by sputtering on the quartz substrate. The influences of the growth conditions to the morphology of the ZnO films have been examined. Amorphous gel-like deposits were observed at 30°C. Both amorphous gel and ZnO crystals were deposited at 40°C. Above 55°C, ZnO mono-particulate films with few particles being observed on them were obtained. The morphology of the ZnO depended on the concentration of Zn (0.01-0.5 mol•dm^-3). In a low Zn concentration, spindle-shaped particles composed of fibers were deposited. In a high Zn concentration, platelet deposits of a few micrometers were observed. For deposition of hexagonal shape ZnO, the Zn concentration of 0.05 mol•dm^-3 was suited. The concentrations of DMAB (0.001-0.05 mol•dm^-3) did not influence the morphology of the deposits. At 55°C, the deposition began just after soaking in the solution. Initially, the agglomerated particles of about 200 nm composed of small particles (10-30 nm) were deposited. According to the particle growth, the particles became hexagonal in shape. The hexagonal ZnO particles grew to micron sizes by the reaction for 4 h. At high reaction temperatures, the initial nucleation density was higher, and ZnO films of finer particles were obtained in a short period. After the catalyst layer was covered by ZnO, the growth rate became slow, but the growth continued due to the thermal decomposition of DMAB.

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SnO₂ thin film was prepared from a SnF₂-HF aqueous solution with the addition of H₃BO₃ aqueous solution by the Liquid Phase Deposition (LPD) method. We focused on the construction of the continuous deposition system and the control of the deposition rate. Parent solution containing SnF₂-HF was intermittently added to the treatment solution, which consists of the excess amount of H₃BO₃. As a result, the deposition rate can be maintained almost constant, at least for 24 h, and uniform SnO₂ film with the thickness of more than 600 nm was obtained.

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Mixing states for aqueous solutions of water-miscible organic solvents, acetonitrile and 1,4-dioxane, have been investigated at the molecular level by means of small-angle neutron scattering (SANS) and NMR relaxation. It has been shown that the organic solvent and water molecules are inhomogeneously mixed each other at the molecular level, although their mixtures are homogeneous at the macroscopic scale. Thus, both organic solvent clusters and water clusters coexist in the mixtures. The present investigation has also revealed that the microinhomogeneity of acetonitrile-water and 1,4-dioxane-water mixtures is gradually enhanced by cooling or adding salts toward phase separation. Based on the results, the effect of microinhomogeneity for solvent mixtures on chemical reactions was considered.

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The magnetite nanoparticles were synthesized through a process including dissolution of Fe(OH)₂ and precipitation of an oxidized phase under ultrasonic irradiation in an aqueous solution. It was found that the ultrasonic irradiation accelerated the formation of magnetite. The crystallinity and magnetic properties of the magnetite particles synthesized under ultrasonic irradiation were better than those synthesized under mechanical stirring. The effects of dissolved gas and pH value were also studied. The dissolved gas was important to the effect of ultrasound on the formation of magnetite and the properties of particles were different when different gases were used as dissolved gas in the sonochemical synthesis of magnetite. The magnetite particles were successfully synthesized even at a neutral solution under ultrasonic irradiation. The low pH value delayed the formation of magnetite and affected the morphology of magnetite particles.

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A continuous series of solid solutions in the system of strontium and lead hydroxyapatite, Pb_xSr_1-xHAP (x=0-1), was successfully synthesized by low-temperature mixing method (LTMM) at 160°C for 12 h under hydrothermal conditions. The samples were characterized by chemical analysis, electron microscopic observation and X-ray powder-pattern fitting. The site of the metal ions in the solid solutions was analyzed by the Rietveld method. The lattice constants of the prepared solid solutions varied linearly with Pb contents. It was found that Pb²⁺ ions in the solid solutions preferentially occupied the M(2) site in the apatite structure.

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Silica-coated magnetite nanoparticles were synthesized via sol-gel process, which comprises the hydrolysis and condensation of TEOS in ethanol/water solution with NH₃ aq. as catalyst. Transmission electron microscope and vibrating sample magnetometer was applied to characterize the nanocomposite particles. Results reveal that the reaction parameters including volume ratio of alcohol/water, the concentrations of NH₃ aq and TEOS play important roles of the formation of silica shell. The thickness of silica shell increased with TEOS concentration. The nanocomposite particles remained favorable superparamagnetism. The formation of silica shell mainly came from the aggregative growth of silica primary particles on the surface of magnetite nanoparticles.

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Bimodal porous silica gel with both macropores and mesopores was prepared from water glass (WG) in the presence of low-molecular-weight surfactant, sodium dodecyl sulfate (SDS), by inducing phase separation during sol-gel reaction. The macroporous morphology was controlled by changing starting composition and gelation temperature: the change in the concentration of SDS was effective to control connectivity of macropores and silica gel skeleton in micrometer size, and the gelation temperature significantly affected macropore size. From the change in morphology with the concentration of SDS, it is considered that a homogeneous reacting solution separated into a phase of SDS and that of polymerized silica in contrast to other silica-surfactant systems, where phase separation proceeds between solvent and surfactant associated with silica gel surface. It is also suggested that SDS forms associated complex or micelle in aqueous acidic solution, and the formation of such structure plays an important role in the phase stability. We also controlled mesopore structures in the macroporous silica gel by aging as-geled samples under basic conditions.

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Interfacial reaction in a multiple emulsion, was carried out with the aim of preparing hollow hydroxyapatite (HAp) microspheres. The multiple emulsion was a W/O/W emulsion, made of dipotassium hydrogen phosphate solution as an inner aqueous phase, cyclohexane as an oil phase, and calcium nitrate solution as an outer aqueous phase. The phase diagrams of Ca(NO₃)₂-K₂HPO₄-H₂O system were drawn by thermodynamic computations and used to simulate the chemical process in a multiple emulsion for determining the experimental conditions. Single phase HAp was synthesized at an initial pH of 12.0. HAp with a Ca/P ratio was measured by inductively coupled plasma spectroscopy to correspond to 1.49. The product was composed of microspheres of 0.5 to 2 μm in diameter. Each microsphere was composed of acicular particles with an aspect ratio of 2.5-10 with a short axis length of about 20 nm.

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Large plate crystals of boehmite up to 4 μm were prepared from Al(NO₃)₃ solutions with the addition of NaOH under hydrothermal conditions at 250°C for 6 h. The conditions to obtain monodispersed boehmite large plate crystals were determined to be in the range of OH/Al molar ratio from 3.5 to 3.8 and Al concentration from 1.3 to 2.0 mol/kg. Bayerite formed by mixing the starting materials changed to gibbsite at 200°C, and at the same time boehmite started to crystallize from gibbsite. Even after complete phase change from gibbsite, small boehmite crystals grew larger by dissolution and precipitation mechanism. The key to obtain boemite large plate crystals is the preparation of homogenous fine boehmite crystals by quickly heating fine gibbsite crystals to the boehmite stable region, as well as the selection of OH/Al molar ratio and Al concentration.

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The layered structure of H₄Nb₆O₁₇ prepared by the proton exchange of K₄Nb₆O₁₇ was modified by using various n-alkylamines as swelling agents to enlarge the interlayer space. The incorporation of TiO₂ into the interlayer space was also attempted. XRD, EDX, and TG-DTA measurements were employed to characterize the products. The photocatalytic activities were evaluated by NO_x destruction under photo-irradiation with different light wavelengths. The results showed that the photocatalytic activity of a layered compound could be significantly promoted just by enlarging the interlayer space of it. And the incorporation of TiO₂ could further enhance the activity.

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Layered double hydroxide (LDH) has positive charge between the layers and is known as anion exchangeable clay being able to intercalate various organic and inorganica nions. In this study, organic-inorganic layered nanohybrids were prepared by intercalation of organic carboxylate anions into Zn/Al LDH in an aqueous solution. Four intercalation compounds were prepared by the reactions of succinate, terephthalate, 4-pyridinecarboxylate, and p-hydroxybenzoate anions with Zn/Al LDH in aqueous solution. Interlayer spacing of these four intercalation compounds decreased by the thermal treatment at 363 K, and recovered by the treatment in water, reversibly.

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Alumina with nanoholes was prepared by anodic oxidation of aluminium and subsequently the synthesis of Fe nanofibers was attempted using nanoholes in alumina as a template. Various Fe nanofibers were synthesized by electroplating into alumina templates and subsequent chemical treatments in mixed-acid solutions to remove the templates. Obtained Fe nanofibers had the dimension with 20 nm-30 nm in diameters and typically 500 nm-2 μm in length. Effect of anodic oxidation treatments for a template on the microstructure of Fe nanofibers was examined. The length of Fe nanofibers could be changed by modifying the synthetic conditions, such as anodic oxidation times and electroplating times.

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The growth of inorganic particles with chemical zoning is studied with the reaction-diffusion in gel. The two kinds of cations Ca²⁺ and Mg²⁺ diffuse into a gel, and a reactive anion CO₃ ^2- diffuses from the opposite side. The distinct chemical zoning was generated in the particles formed in the agar and in the restricted concentration range of the electrolytes in the reservoir. No chemical zoning is observed in gelatin. The particle structure is significantly affected by the gel type especially in the early stage of the growth. These characteristics can be understood taking into account the difference in the diffusion rates of the two kinds of cations. When several kinds of cation pairs are used, there is a pair that forms a novel stripe pattern of the precipitates. The pattern is also controlled by the difference in the diffusion rates of two kinds of cations.

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Fluorite-type CeO₂ nanorods were synthesized from aqueous CeCl₃ solutions containing polyethylene glycol, NaOH, and NaCl. The solutions were hydrothermally treated at 140°C, resulting in the formation of nanorod-like precipitates. Further annealing of the precipitates led to the growth into well-defined nanorods 5-10 nm in diameter and 50-200 nm in length. It was found that the addition of NaCl to the solution could enhance the one-dimensional growth of CeO₂ and reduce the degree of aggregation. A high-resolution transmission electron microscopic observation revealed that the nanorod was single-crystalline and its growth direction was along the [110] axis of the cubic CeO₂ structure. Our results then demonstrated that the unusually [110]-oriented CeO₂ nanorods could be grown by a facile synthesis method.

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In this work we applied a “micro-gel spray freeze-drying method” for synthesis of YVO₄:Eu³⁺ phosphor materials. The proposed approach combined usual freeze-drying technique with water soluble polymers: agarose, gelatin and PVA to reinforce the frozen particles due to gel formation. The nature and concentration of these water soluble compounds determine the structure of the gels, and thus it allows controlling microstructure of the ice particles. It was found that a polymer and its concentration affects the morphology of the primary particles and prevents aggregation of secondary particles during freeze-drying as well as during thermal treatment of the precursors in synthesis of YVO₄:Eu³⁺ phosphor.

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Yttrium aluminum garnet, Y₃Al₅O₁₂, (YAG) monoliths with well-defined macropores have been prepared from ionic precursors using the sol-gel method accompanied by phase separation. The addition of propylene oxide to the starting solution controls the gelation, while the addition of poly(ethylene oxide) induces the phase separation. Polymerization-induced phase separation and gelation concur by an appropriate selection of the starting composition, which allows the production of bicontinuous macroporous nanocomposite gels in large dimensions (~10×10×10 mm³). During heat treatment at 800°C, the monolithic nanocomposite gels crystallize into YAG without the formation of any intermediate phases or the precipitation of impurity phases, indicating higher homogeneity of cation distribution in the dried gels. The macroporous YAG network was maintained even after heat treatment at 1000°C for 10 h.

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Iron group metal sulfides were synthesized from the elements under hydrothermal condition. For nickel sulfides, two kinds of nickel metal powder, coarse powder passed through 63 μm mesh and fine powder passed through 3 μm mesh, were used as the starting materials. The reaction with the coarse Ni powder gave NiS with appreciable amount of Ni, Ni₃S₂, and Ni₉S₈. Pure NiS was obtained by the reaction with the fine Ni powder at 240°C for 10 h. The lowest nickel sulfide Ni₃S₂ was obtained as a single phase product of the reaction if the coarse Ni powder was used. From these results, the fine and coarse powders were found to be suitable for the syntheses of NiS and Ni₃S₂, respectively. The lowest cobalt sulfide Co₉S₈ was obtained almost as a single phase though the XRD pattern of the product showed some unidentified peaks. Pure Co₉S₈ was obtained by washing the reaction product with HNO₃. In the Fe-S system, FeS was obtained with a small amount of Fe₃O₄.

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We synthesized needle-shaped Ag₂CO₃ and triangular plates of Ag by applying ultrasonic irradiation to the solid-liquid system, Ag₂O/H₂O. The samples obtained were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and inductively coupled plasma emission spectrometry (ICPES). The ICPES data confirmed that ultrasonic irradiation increased the solubility of Ag₂O in distilled water. Applying low-frequency ultrasonic irradiation accelerated the dissolution of Ag₂O and enabled needle-shaped Ag₂CO₃ and the triangular plate of Ag to be obtained by freeze-drying, while applying high-frequency ultrasonic irradiation almost reduced Ag₂O to Ag. A variety of silver related materials could be synthesized using this water-based ultrasonic process that was environmentally friendly without adding a surfactant.

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Highly transparent ZnO thin films were prepared by calcining ZnO₂ precursor films deposited from aqueous solutions. The transparency of the resultant ZnO thin films, which was directly associated with that of the precursor films, depended on the kind of zinc source, the composition of the starting solution, and the deposition temperature of the ZnO₂ precursor. The most highly transparent ZnO thin film was obtained by calcining a ZnO₂ precursor film which was deposited from a solution containing 0.01 mol/dm³ of ZnSO₄, 1.8 mol/dm³ of H₂O₂, and 2.1 mol/dm³ of NH₃ at 303 K. Doping of a ZnO thin film with indium was attempted by an immersion of the thin film in an In(NO₃)₃ solution and a subsequent heat-treatment at 773 K in a N₂ atmosphere, which resulted in an electrical conductivity of 535 S/m.

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Nanometer-sized M^IIIM^VO₄ (M^III:La, Y; M^V:V, P) particles doped with Ce³⁺ ions were prepared from alkaline alcohol-water mixture with M^III (NO₃)₃, CeCl₃ and H₃PO₄ (or NH₄VO₄) under reflux (355 K). The maximum peak position of photoluminescent emissions for M^IIIM^VO₄:Ce particles centered around 350-450 nm were strongly affected by host anions (PO₄ ^3-, VO₄ ^3-) in contrast to host cations (La³⁺, Y³⁺). The maximum external quantum efficiency in this work was 18.3% for LaPO₄ nanocrystals doped with 0.5 mol% of Ce³⁺ ions, whereas those of M^IIIVO₄:Ce were extremely low since most of Ce³⁺ ions added in the ethanol-water mixture were oxidized to Ce⁴⁺ ions under reflux.

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Triangle and hexagonal microsized gold plates with nanometer thickness were synthesized through a simple solution route: mixing an ethanol solution of 3-mercaptopropyltrimethoxysilane (MPTMS) and an aqueous solution of hydrogen tetrachloroaurate (HAuCl₄•4H₂O). The prepared gold plates were single crystal, and the size of gold plates was changed from submicrometers to several tens of micrometers depending on the conditions after mixing. We also examined the products obtained when 1-hexadecanethiol (1-HT) or 2-mercaptoethanol (2-ME) were used instead of MPTMS. It was found that in both the cases gold plate is just a minor product. It is deduced that the methoxy groups as well as thiol group of MPTMS play important roles in formation of gold plates.

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This review describes recent progress in the development of hydrogen-permselective ceramic membranes derived from organometallic precursors. Microstructure and gas transport property of microporous amorphous silica-based membranes are briefly described. Then, high-temperature hydrogen permselectivity, hydrothermal stability as well as hydrogen/steam selectivity of the amorphous silica-based membranes are discussed from a viewpoint of application to membrane reactors for conversion enhancement in the methane steam reforming reaction, which leading to development of a novel highly efficient hydrogen production system. Novel nickel (Ni)-nanoparticles dispersed amorphous silica-based membranes with a unique hydrogen permselectivity, and polymer-derived amorphous Si-(B)-C-N membranes having enhanced thermal and chemical stability are also discussed to develop novel ceramic membranes for high-temperature separation of hydrogen.

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Blue-emitting strontium magnesium halophosphate phosphor particles were prepared by spray pyrolysis from the spray solutions with ammonium chloride. The ammonium chloride was used as the source of chlorine and the flux material. The prepared (Sr, Mg)₅(PO₄)₃Cl : Eu²⁺ phosphor particles had regular morphologies and fine sizes. The mean sizes of the (Sr, Mg)₅(PO₄)₃Cl : Eu²⁺ phosphor particles were each 1.2 and 1.9 μm when the ratios of strontium to chlorine components were 1 : 0.5 and 1 : 1. The ratios of strontium to chlorine components in the as-prepared and post-treated particles were each 1 : 0.26 and 1 : 0.21. The (Sr, Mg)₅(PO₄)₃Cl : Eu²⁺ phosphor particles that were prepared from the spray solution with the ratio of strontium to chlorine components of 1 : 1.5 had the maximum photoluminescence intensity, which was 176% of that of the commercial BaMgAl₁₀O₁₇ : Eu²⁺ phosphor particles under excitation wavelength of 400 nm.

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The samples corresponding to the partial replacement of Sr by Ce in SrBi₂Ta₂O₉, Sr_1-xCe_xBi₂Ta₂O₉ (x=0.1, 0.2, 0.3) and Bi₄Si₃O₁₂, Bi₂SiO₅ added Sr_1-xCe_xBi₂Ta₂O₉ were obtained by the solid-state reaction, and we investigated the relationship between the ferroelectric properties and crystal structure of these materials. From the P-E hysteriesis measurement, Sr_0.8Ce_0.2Bi₂Ta₂O₉ has a higher Pr and lower Ec. Pr increased and Ec decreased by adding Bi₄Si₃O₁₂ or Bi₂SiO₅ to Sr_0.8Ce_0.2Bi₂Ta₂O₉. We examined the effects of the Ce substitution and adding Bi₄Si₃O₁₂ or Bi₂SiO₅ to Sr_1-xCe_xBi₂Ta₂O₉ on the tilting of the TaO₆ octahedron. Sr_1-xCe_xBi₂Ta₂O₉ and that added with Bi₄Si₃O₁₂ or Bi₂SiO₅ had a higher spontaneous polarization, and a smaller tilting angle (α_a) of the TaO₆ octahedron when compared to those of SrBi₂Ta₂O₉.

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Structural ceramics are brittle and sensitive to flaws. As a result, the structural integrity of a ceramic component may be seriously affected by inherent flaws. Self-crack-healing is an excellent answer to this problem. At the moment, however, there is no technique to heal embedded flaws. Therefore, a technique to guarantee the reliability of ceramics components is demanded, and thus a technique using crack-healing followed by proof test was developed by K. Ando et al to accomplish this. With this technique, testing on the mechanical behavior of the crack-healed zone is very important for ensuring the structural integrity of ceramic component. In this study, firstly Al₂O₃/SiC composite with excellent crack-healing ability was sintered. Secondly, a semicircular groove was hardly machined using a diamond ball-drill. Third, a proof test was carried out on the crack-healed sample. Last, using the crack-healed and proof-tested sample, a fracture test was carried out at 1373 K. The measured local fracture stress (σ_LF) was compared with the theoretical minimum fracture stress guaranteed (σ_G ^T) at 1373 K. As the results, σ_G ^T showed good agreement with the σ_LF at 1373 K. Thus, the crack-healing followed by proof test was an excellent technique to guarantee the reliability of machined Al₂O₃/SiC composite.

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Mass loss and mechanical properties including density and morphology of Si₃N₄ ceramics sintered in air and in N₂ atmospheres were comparatively studied. The trends of mass loss with increasing temperature of the Si₃N₄ sintered in air and in N₂ atmospheres were significantly different. The densities of the specimens sintered at the same temperature both in air and in N₂ atmospheres were similar. However, the mechanical properties of the materials sintered in air were lower than those sintered in N₂ atmosphere. Vickers hardness (H_V), fracture toughness (K_IC) and biaxial flexure strength of the specimens sintered in air and in N₂ atmospheres were 12.7 GPa, 5.5 MPa•m^1/2 and 263 MPa, and 13.3-13.5 GPa, 6.0-6.8 MPa•m^1/2 and 340-406 MPa, respectively.

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Ba-deficient non-stoichiometric compositions of Ba_5-xNb₄O_15-x (x=0 to 0.5) have been investigated for the purpose of improving microwave dielectric properties. While there was no significant variation in dielectric constant, variations in Q×f and TCF (temperature coefficient of frequency) values with the degree of Ba deficiency were prominent. Near zero TCF value was obtained for the composition of Ba_4.77Nb₄O_14.77. The apparent formation of a second BaNb₂O₆ phase for the Ba-deficient compositions was believed as responsible for the improved TCF. It was interesting to note that the second phase was present more preferably inside of the sample.

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Silicon carbide powder, polycarbosilane (PCS) and xylene mixed slurries were prepared for viscosity measurement and microstructure observation. Absolute slurry viscosity and shear rate dependence of viscosity were investigated at various SiC concentrations and particle sizes. Temperature dependence of viscosity was also investigated. As the primary particle size in powders decreases, viscosity increases relatively at a low SiC concentration. Microstructure observation on diluted slurries revealed the existence of secondary particles composed with primary nanoparticles and network formation by physically or chemically contacted secondary particles. Some of the microstructure changes with shearing was consistent with a strong shear thinning phenomenon of slurry viscosity.

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Exergy is a measure which can commonly deal with the quantification of the variety of resources, products and energy coming in and going out the systems in manufacturing process. In this study, exergy consumption analysis was performed on ceramic parts. The exergy of the intrinsic to the materials and energy were calculated and then the degree of process efficiency (defined as the ratio of fixed energy to input in this report) was evaluated. Results revealed that the process efficiency was 5.5% in total, suggesting that the most part of input exergy was lost as a thermal enthalpy and wastes. Particularly, a lot of exergy was consumed and the process efficiency was low in granulation and sintering steps, then, the approaches to improve the efficiency were discussed.

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Carbon film was coated on the surface of ZnO chip by pyrolysis of poly(vinyl alcohol) with different polymerization degrees, and then longevity of a cut flower, such as carnation, was studied by adding carbon-coated ZnO chip in the vase filled with distilled water. In the results of optimum condition for coating ZnO with carbon, it was clarified that poly(vinyl alcohol) with polymerization degree of 2000 was suitable for forming homogeneously carbon at every portion in ZnO chip. From observation of carnation, it was found that the formation of carbon on ZnO chip was effective for longevity of a cut flower.

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