In order to attain further performance improvements concerning UV-shielding, the synthesis parameters of plate-like lepidocrocite related potassium lithium titanate were optimized and calcia-doped ceria (Ce_0.8Ca_0.2O_1.8) nanoparticles were coated on plate-like potassium lithium titanate (K_0.8Li_0.27Ti_1.73O₄), 10-20 μm in diameter via solution processes, where the plate-like titanate was prepared by reacting K₂CO₃, Li₂CO₃ and TiO₂ using KCl flux at 950°C. After putting plate-like potassium lithium titanate particles in deionized water at 40°C, appropriate quantities of 3 M NaOH aqueous solution and 0.8 M CeCl₃-0.2 M CaCl₂ mixed aqueous solution were simultaneously dropped, where the solution was stirred and pH was kept at 12 throughout the reaction. Then, the desired amount of 2 M H₂O₂ solution was added and pH was also kept at 12. The slurry was filtrated and washed with water and methanol. The precipitate was fired at 700°C for 1 h to obtain plate-like K_0.8Li_0.27Ti_1.73O₄ coated with white Ce_0.8Ca_0.2O_1.8 nanoparticles. Such panoscopic assembling successfully improved the comfort of the product when wearing it on the skin without compromising the UV-shielding ability, meanwhile greatly reducing the oxidation catalytic activity.

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Ternary lanthanide iridium oxides Ln₃IrO₇ (Ln=Pr, Nd, Sm, and Eu) were prepared and their structures were determined by X-ray diffraction measurements. At room temperature, Pr₃IrO₇ crystallizes in an orthorhombic superstructure of cubic fluorite with the space group Cmcm. The results of the differential thermal analysis (DTA) and specific heat measurements show the existence of a phase transition for Ln₃IrO₇ (Ln=Pr, Nd, Sm, and Eu) at 262, 342, 420, and 485 K, respectively. At low temperatures, Ln₃IrO₇ crystallizes in a monoclinic structure with the space group P2₁/n. These results for Ln₃IrO₇ are compared with those for Ln₃MoO₇, Ln₃RuO₇, Ln₃ReO₇, and Ln₃OsO₇.

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Lines consisting of ferroelectric β′-Gd₂(MoO₄)₃ crystals are patterned on the surface of NiO (2 mol%)-doped 21.25Gd₂O₃·63.75MoO₃middot;15B₂O₃ glass by continuous wave (cw) Nd: YAG laser irradiations with a wavelength of λ=1064 nm, where laser energies absorbed by Ni²⁺ ions are converted to the local heating of surrounding Ni²⁺ ions. The surface morphology of crystals in the patterned lines is clarified from confocal scanning laser microscope observations. β′-Gd₂(MoO₄)₃ crystal lines patterned by laser irradiations with a power of 0.73 W and a scanning speed of 2.5 μm/s show a smooth surface with a bump (width: 9 μm, height: 3 μm), and it is suggested from polarized micro-Raman scattering spectra that β′-Gd₂(MoO₄)₃ crystals might orient along the laser scanning direction. The present study demonstrates that the transition metal atom heat processing, i.e., a combination of cw Nd:YAG laser and Ni²⁺ ions, is a novel technique for spatially selected crystallization in rare-earth containing glasses.

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Gel combustion synthesis was investigated on rare earth aluminates, especially gadolinium aluminate, by adjusting Gd/Al ratios in mixed nitrate aqueous solution and the kinds of fuel. Use of urea as the fuel was essential to obtain the crystallized oxides as the combustion products in any Gd/Al compositions although glycine fuel gave amorphous products in their aluminum-rich composition. FT-IR measurements showed that urea molecules coordinated to both aluminum and gadolinium ions, but that glycine molecules only to the latter to form their coordination polymer. The coordination polymer contributes not only to obtain homogeneously mixed gel in the starting material but also to the explosive combustion leading to high temperature reaction.

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CeO₂ colloidal particles with a mean crystallite size of 2 nm synthesized by a solvothermal reaction were coagulated with 1 mol/L solutions of various bases: NaOH, NH₄OH, Na₂CO₃, (NH₄)₂CO₃, NaHCO₃, and NH₄HCO₃. The CeO₂ powders obtained by calcination of the coagulated products at 300°C had almost the same crystallite sizes in a range of 4-5 nm, while their BET surface areas were considerably different. The CeO₂ powders coagulated with Na₂CO₃ and NH₄OH had large surface areas due to micropores, and the powders obtained using NaHCO₃ and (NH₄)₂CO₃ had large pore-volumes derived from macropores. A series of Ru/CeO₂ catalysts were prepared by a precipitation-deposition method, and characteristics of the Ru species supported on these CeO₂ powders having different pore structures were examined in the liquid phase oxidation of benzyl alcohol. The Ru species having well-crystallized RuO₂ bulk state showed only low activities. On the other hand, well dispersed Ru species exhibited high activities. The pore structure of CeO₂ affected the states of the Ru species loaded, and, consequently, affected their activities for the oxidation. Ruthenium species were not loaded on the surface inside the micropores by the preparation method adopted in this work. Accordingly, the Ru/CeO₂ catalysts with large surface areas derived from meso- and macro-pores had well-dispersed Ru species and showed high activities, which were much higher than that of the Ru/CeO₂ catalyst prepared by a conventional co-precipitation method.

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Porous praseodymium oxysulfate, Pr₂O₂SO₄, with a large oxygen storage capacity was prepared from precipitates, which were formed by adding (NH₄)₂SO₄ to a mixed aqueous solution of Pr(NO₃)₃ and cationic surfactant, CTA (cetyltrimethyl ammonium ion). Heating the precipitate, Pr-SO₄-CTA, yielded directly the single phase of Pr₂O₂SO₄ at a low temperature of 300°C, compared to ≥800°C required for the decomposition of Pr₂(SO₄)₃ (Pr-SO₄), and compared to ≥500°C required for the mesophase of Pr and dodecyl sulfate (Pr-DS) in our previous study.¹⁾ The effect of preparation route on microstructure and oxygen release/storage property of Pr₂O₂SO₄ was studied by using XRD, TG, SEM, N₂ adsorption and catalytic reaction. In contrast to the macropores (≥30 nm in size, 8 m²g^-1) of Pr-SO₄ and mesopores (≤10 nm, 28 m² g^-1) of Pr-DS, Pr-SO₄-CTA showed a wide pore size distribution in the range 2-40 nm and a larger surface area of 37 m² g^-1. The porous structure is very effective in increasing the rate of oxygen release as well as storage. The anaerobic CO oxidation of 1 mass% Pd-loaded Pr₂O₂SO₄ was evaluated in CO/O₂ cycled feed stream reactions. It was found that the catalyst prepared from Pr-SO₄-CTA achieved the highest catalytic activity due to the high porosity and specific surface area.

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Fabrication of EuO-Al₂O₃-B₂O₃-SiO₂ glasses with high-concentration of Eu²⁺ ions was attempted in N₂ gas with an IR-image furnace and rapid quenching in twin rollers. Their magnetic susceptibilities of these glasses obeyed the Curie-Weiss law with the negative Curie temperature at temperatures higher than 50 K, while Eu²⁺ ions coupling by a superexchange-type mechanism involving oxygen ions at temperatures lower than 50 K showed a ferromagnetism. From their magnetization data at lower temperatures, we estimated an amount of Eu²⁺ ions in the glasses, in whose fabrication process a part of Eu²⁺ ions were oxidized to Eu³⁺. We also measured FT-IR and Raman spectra and discussed the stable valence state of europium ions in the studied glass-matrixes.

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Transparent glass ceramics containing fluorite nano-crystals were developed from oxyfluoride glasses containing 32 mol% SrF₂ doped with Pr³⁺ and Yb³⁺ ions. Materials containing xSrF₂+(32-x)CaF₂ were also prepared and their fluorescence properties were investigated. Fluorite solid solution crystals containing lanthanide ions were precipitated as a single phase in all the glass ceramic compositions by heat-treatment at appropriate temperatures. The glass ceramics showed Pr³⁺: 1.3 μm emission, the intensity of which became stronger with increasing SrF₂ content and heat-treatment temperature, while only the 1 μm emission of Yb³⁺ was observed in all the as-made glasses. The lattice constant of fluorite crystals increased with increasing Sr content. Among all the samples, the glass ceramic sample with 32 mol% SrF₂ showed the strongest 1.3 μm emission.

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Terbium (III) ion-doped zirconia (ZrO₂:Tb³⁺) thin films have been directly prepared on soda-lime glass and Si wafer by the liquid phase deposition (LPD) method. The stabilization of Tb³⁺ ion in the LPD reaction solution, containing fluoride anions, was successfully achieved by using DTPA (diethylenetriaminepentaacetic acid) as a masking reagent. Preparation composition of ZrO₂:Tb³⁺ thin film was determined by inductively coupled plasma-atomic emission (ICP-AES) microscopy analysis. The structural and luminescence properties for the deposited films were analyzed. After annealed at 900°C, the deposited film shows characteristic strong emission assigned to ⁵D₄→⁷F₅ of Tb³⁺ under CT band excitation.

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The methodology of parallel synthesis based on the polymerizable complex method is described in this work. A model system such as A_xGa_yO_z (A=Mg, Ca, Sr, Ba) was used to test the proposed approach and to find potential hosts for Tm³⁺ activated blue light emission phosphor materials. It was found that Ca-containing compounds as hosts are superior to the other alkaline-earth containing materials in this system. The composition Ca₅Ga₆O₁₄:Tm³⁺ demonstrated excellent color purity with CIE coordinates x=0.16, y=0.12 and it had emission intensity corresponding to the 68% peak intensity of commercial BAM ((Ba, Eu)MgAl₁₀O₁₇)-one of the strongest blue emission phosphor.

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In this study we introduce a two-step strategy for the synthesis of BaAl₂S₄:Eu bulk samples. The first step involves synthesis of a BaS:Eu intermediate by a sol-gel/polymerizable complex method, which provides a highly homogenous distribution of Eu in the BaS. The second step involves solid-state reaction between the BaS:Eu intermediate with Al₂S₃ in an ampoule at high temperature. It was found that phase purity increases with increasing synthesis temperature and almost single-phase samples can be obtained at above 900°C. However, BaAl₂S₄:Eu samples synthesized at lower temperatures produced more intense emission. To the best of our knowledge, this is the first time a solution method has been used in the preparation of BaAl₂S₄:Eu.

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This work has investigated luminescence properties of SrSi₂O₂N₂: Eu²⁺ phosphors synthesized by a new method using Sr₂SiO₄: Eu²⁺ as a precursor. Compared with a conventional solid-state reaction method, this method provides increased crystallinity and luminescence efficiency. X-ray diffraction analysis has indicated that SrSi₂O₂N₂: Eu²⁺ formed as an almost single-phase, but chemical analysis has shown that obtained samples have an oxygen/nitrogen atomic ratio deviated from the stoichiometric composition. It can be expected that luminescence efficiency of this phosphor will be higher for the stoichiometric composition than for non-stoichiometric ones. Under 460 nm excitation, this phosphor shows an emission band peaked at 538-564 nm for varied Eu²⁺ concentration, and shows the maximum at 15 mol% with high integrated photoluminescence intensity, which is about 1.05 times as high as that of the commercial yellow phosphor, (Y,Gd)₃Al₅O₁₂: Ce³⁺ (P46-Y3).

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Divalent europium ion doped metal nitride phosphor, of Sr₂Si₅N₈:Eu²⁺, was synthesized by using Sr carboxylates as a reducing agent and the preparation conditions were optimized. The obtained samples derived from Sr acetate doped with 4 at% Eu²⁺ to Sr content showed a strong emission at about 630 nm under the excitation at 449 nm. The emission intensity was about 136% of that of a commercially available YAG:Ce³⁺ (P46-Y3) standard phosphor, and the residual oxygen and carbon contents were 0.88 and 0.04%, respectively. All these values were better than those for the same composition of Sr₂Si₅N₈:Eu²⁺ prepared by the conventional CRN method. The excellent quality and the suitable CIE chromaticity coordinates of (0.645, 0.355) suggest that this phosphor is one of possible candidates for the red color component of white LEDs.

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Iron element was extracted from the rare earth magnets (Nd-Fe-B and Sm-Fe-N type ones) scrap by the carbonylation reaction with a small amount of sulfur as a catalyst. Both scrap hardly reacted with carbon monoxide, and conversion to iron carbonyl complex was about 30-70% evaluated by energy dispersion X-ray analysis. After the disproportionation of their primary intermetallic phase by hydrogenation or thermal decomposition, the extraction rate for Fe element was significantly accelerated to produce Fe(CO)₅ with the higher yield (~92%) since the high reactive Fe particles against carbonylation was precipitated as the iron-based nanocomposites by the above treatments. Additionally, the simultaneous extraction of Fe(CO)₅ and decomposition of it with naphthalene in the autoclave vessel was carried out, resulting in the formation of Fe₃C/carbon nanowire composites. The resin compact including the resultant Fe₃C/carbon nanowire composites showed the good electromagnetic wave absorption ability in a GHz range.

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We investigated the thermal stability and microstructural changes of lanthanum modified γ-alumina prepared by impregnation process, using aqueous lanthanum (III) nitrate. 0.1-10 mol% La added aluminas were heated in the temperature range of 600-1400°C and characterized by surface area measurement, X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), differential thermal analysis (DTA), scanning electron microscope (SEM), and transmission electron microscope (TEM). At 1200°C, the surface area of 0.3 and 1.5 mol% La modified aluminas were 82 m² g^-1, while that of pure alumina was 45 m² g^-1. Even at 1300°C, the surface area of 5 mol% La modified alumina maintained 24 m²/g. The solid state reaction of lanthanum oxide with alumina formed LaAlO₃ nanoparticles in the secondary particles of alumina. At 1300°C, LaAl₁₁O₁₈ was formed by the reaction of LaAlO₃ with Al₂O₃.

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A series of perovskite-type LaTiO₂N materials with compositions a slightly deviated from the stoichiometric metal composition was prepared. The cation nonstoichiometry in the oxynitrides affected not on the bandgap but on the reflectivity. It seemed that the more ratio of titanium to lanthanum resulted in lower reflectivity.

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Surface morphology of perovskite-type oxide, LaFeO₃, prepared by thermal decomposition of Fe(III)La(III) heteronuclear coordination polymer, La[Fe(CN)₆]·nH₂O, was compared with those of LaFeO₃ obtained by two conventional preparation methods, solid-state reaction of Fe₂O₃ and La₂O₃ and pyrolysis of a co-precipitated {Fe(OH)₃+La(OH)₃} precursor. At 1273 K, the first method gave LaFeO₃ with submicrometer-sized pores being highly ordered. At the same temperature, the LaFeO₃ particles with various sizes from nano-to micrometer in diameter and the highly sintered LaFeO₃ were obtained by solid state reaction and co-precipitation method, respectively.

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Electrical conductivity of a series of Ln_9.33+x/3Si_6-xM_xO₂₆ (Ln=La, Nd and Sm, M=Al and Ga) sinters was examined. The pre-exponential factor and activation energy of the ionic conduction were well related by Meyer-Neldel rule, i.e., G=G₀₀ exp (ΔE/kT₀) exp (-ΔE/kT). Most of the sinters were composed with an apatite-like phase in major and sub-products such as LnSiO₅ and Ln₂O₃ in minor proportions. The single phases with apatite-like structure were obtained for the composition of x=1.5. At this composition, the activation energy increased with a decrease in the ionic radius of Ln. The lowest activation energy and highest pre-exponential factor were observed for the combination of Ln=La and M=Al. This result was interpreted by considering the formation of the 4e sites for oxygen with under occupancy and oxygen ion interstitials surrounded with six 6h(La) sites.

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Dielectric properties of SrO substituted BaTi₂O₅, Ba_1-xSr_xTi₂O₅ prepared by arc melting were investigated. Due to the thermal instability of BaTi₂O₅ at high temperatures, the decomposition of BaTi₂O₅ was accompanied with solid solution of SrO in BaTi₂O₅. Lattice parameters of Ba_1-xSr_xTi₂O₅ decreased with increasing SrO, and the solubility limit of SrO in Ba_1-xSr_xTi₂O₅ was about x=0.12. A small amount of second phases of BaTiO₃ and Ba₆Ti₁₇O₄₀ were identified at x<0.12 by scanning electron microscopy. Ba_1-xSr_xTi₂O₅ showed a strong b-axis orientation. The Curie temperature (T_c) of Ba_1-xSr_xTi₂O₅ changed in the range between 703 and 750 K depending on SrO content. The dielectric permittivity of Ba_1-xSr_xTi₂O₅ at the T_c was attained to 2700 by substituting SrO of x=0.03. The electrical conductivities of Ba_1-xSr_xTi₂O₅ were lower than that of non-substituted BaTi₂O₅. Ba_1-xSr_xTi₂O₅ containing the second phases showed distorted Cole-Cole semicircles which were deconvoluted into two semicircles based on a Maxwell-Wagner model corresponding to a ferroelectric bulk matrix and paraelectric second phases.

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Several factors, influencing synthesis of Al₄O₄C in carbothermal reduction process from Al₂O₃ and C starting raw materials in argon atmosphere, and oxidation characteristics of Al₄O₄C were investigated. The formed Al₄O₄C in heated specimens was increased and Al₂O₃ and C were decreased with increase of heating temperature and extension of keeping time. Grain size of Al₂O₃ had obvious influence on synthesis of Al₄O₄C and fine Al₂O₃ was more advantageous. The activation energy of the reduction reaction from Al₂O₃ and graphite to form Al₄O₄C was calculated as 358.0 kJ/mol basing on experimental data. Al₄O₄C was observed to be oxidized from about 820°C in air. Al₄O₄C, buried in graphite powder and heated in air, was converted into Al₂O₃ and C.

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Barium titanate nanoparticles were synthesized in water/alcohol solutions by the hydrolysis of complex alkoxide precursor that was prepared by reflux of metallic barium and tetraethylorthotitanate in the alcohol. The alcohols employed were ethanol, 1-butanol and 1-octanol, which have different chain lengths. High hydrolysis reaction temperature produced small particles with small crystallite sizes. Particle and crystallite sizes were also dependent on alcohol species. For ethanol, crystallite size increased from 10.3 to 21.0 nm with an increase in water concentration. The crystallite size also increased from 13.0 to 42.9 nm for 1-butanol and from 26.6 to 52.9 nm for 1-octanol, respectively, with an increase in water concentration. Amorphous or low crystallinity products were formed for the 1-butanol and the 1-octanol at high water concentrations.

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To evaluate the redox nature of magnesium vanadates during the oxidative dehydrogenation of propane, magnesium pyro- and othro-vanadates (Mg₂V₂O₇ and Mg₃V₂O₈, respectively) used for the conversion of propane with and without gaseous oxygen were analyzed by XRD, solid state ⁵¹V MAS NMR and XAFS. After the propane conversion without oxygen, complete conversion of those magnesium vanadates to the corresponding vanadate containing V⁴⁺ or V³⁺ species together with MgO was observed by XRD, while the reduction of V⁵⁺ was detected by ⁵¹V MAS NMR and V K-edge XAFS from those catalysts. However XRD and ⁵¹V MAS NMR revealed that re-oxidation of the reduced Mg₃V₂O₈ resulted in the regeneration of the original phase together with that of a V⁵⁺ species, while the re-oxidation of the reduced Mg₂V₂O₇ afforded a phase (triclinic system) different from the original one (monoclinic system), but, in which the V⁵⁺ species was regenerated from the reduced vanadium.

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Electrochemical micromachining of a metal plate was performed using a solid polymer electrolyte. The fundamental electrolysis system was composed of a metal plate (anode)|polymer electrolyte|tungsten needle (cathode), where the contact diameter of the metal|polymer interface was extremely small (a few μm). The metal substrate was electrochemically oxidized and then Mⁿ⁺ ions migrated to the polymer electrolyte. As a result of the continuous application of a dc voltage to the cell, finer-resolution micromachining (~10 μm) was achieved under room-temperature operation as compared with our previous results obtained using a Na-β"-Al₂O₃ solid electrolyte. Furthermore, the present technique was applicable to many different kinds of metal substrates.

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Thermal processing of powder-derived Ta₂O₅-based ceramics reveals that rapid grain growth associated with a high temperature phase transformation hinders densification, necessitating the development of a reduced-temperature processing methodology. Data are reported for the densification behavior with emphasis on microstructural changes associated with the phase transformation between a stable low-temperature phase (L-Ta₂O₅) and a phase which is stable at high temperatures (H-Ta₂O₅). The H-Ta₂O₅ phase is metastable at room temperature and reverts back to the L-Ta₂O₅ phase with thermal or mechanical treatment. TiO₂ additions stabilize the H-Ta₂O₅ phase and result in enhanced dielectric properties. Because TiO₂ additions decrease the temperature of the densification-hindering phase transformation, an alternate reduced-temperature processing route is necessary. A simple solution-coated powder method was used to produce the first-ever dense and chemically homogeneous TiO₂-modified Ta₂O₅ ceramics in both the L- and H-Ta₂O₅ forms. Thus, this work represents the first comprehensive study of the effects of composition and the L⇒H-Ta₂O₅ phase transformation on microstructural development. The results indicate that the effect of TiO₂ additions on the sintering behavior of Ta₂O₅ ceramics was largely limited to a reduction in the temperature for the densification-hindering phase transformation.

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