In this paper the multi-layer ceramic capacitors (MLCCs) materials research using first-principles calculations are explained. For example, doping with 3d transition metals, particularly Mn, is thought to play an important role in determining the reliability of dielectrics used in MLCCs. However, a detailed examination of the electronic structure, solution energies and compensation mechanisms of these systems is lacking. The quantitative analysis of the substitution of Mn in perovskite-type BaTiO₃ using first-principles calculations in combination with chemical thermodynamics is reported. The solution energies of dopants with vacancy and n-type and p-type charge compensations have been systematically calculated. Substitution onto the two crystallographically different cation sites in cubic BaTiO₃ under four different thermodynamic conditions with different chemical potentials is also examined. Mn is found to be stable on Ti sites under all conditions examined, although its charge state varies. In the oxidizing limit, Mn substitutes for Ti as a Mn⁴⁺ ion, but in the reducing limit, Mn substitutes for Ti as a Mn²⁺ ion compensated by the formation of an O vacancy. Depending on the Fermi level of the system, the valence state of Mn varies from Mn⁴⁺ under p-type conditions, to Mn²⁺ under n-type conditions. Mn³⁺ is not found to be stable. These results agree well with the experimentally determined site preferences and valence states of Mn and help to further elucidate the features of Mn-doped BaTiO₃ at the atomic level.

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Effects of defect structures on polarization hysteresis properties have been investigated for Mn-doped BaTiO₃ ceramics. The polarization hysteresis loops are found to strongly depend not only on the oxygen vacancy concentration ([V_O^••]) but also on the majority-acceptor (Mn³⁺) concentration. Density functional theory (DFT) calculations show that the association of V_O^•• with Mn³⁺ and the following alignment of the defect dipole (V_O^••–Mn³⁺) along P_s (spontaneous polarization) provide an energetically favorable defect structure due to the lowering in energy of the Mn-3d_z² electron. It is concluded that the double-hysteresis-like loop (P-E_double) observed with the high concentrations of V_O^•• and Mn³⁺ originates from the reversible switching of a 90° domain structure stabilized by the formation of the V_O^••–Mn³⁺ // P_s configuration.

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Much attention has been paid to grain boundaries (GBs) in ceramics owing to the impact on material properties. GB atomic scale investigations have so far mostly focused on the major structures. However, actual GB structure is more complex; there could be multiple types of atomistic structure and different morphology such as step and facet. As a case study to characterize these, we report extensive scanning transmission electron microscopy observations for a zinc oxide (ZnO) [0001] 27.8° (Σ13, in the framework of coincidence site lattice theory) tilt GB doped with praseodymium (Pr) in this paper. In addition to the major structure that covers most of the (2570) GB plane area [Sato et al., Phys. Rev. B, 87, 140101 (2013)], two types of metastable atomistic structure are found. One is the secondary structure for the (2570) GB plane area, which is mostly found near facets. The other is a different type of atomistic structure formed in facets. Pr concentration is lower in the secondary structure than in the major structure. It is thus demonstrated that there is a variety in the atomistic structure and chemical composition within a single GB.

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Pherical LiNi_1/3Co_1/3Mn_1/3O₂ particles were successfully synthesized by spray pyrolysis for use as cathode material. The effects of chemical composition on the powder characteristics and rechargeable properties of this material were investigated. Chemical and physical properties were characterized by X-ray diffraction (XRD) and inductively coupled plasma (ICP). XRD revealed that the crystalline phases of the layered structure were obtained upon calcination at 800°C. The chemical composition of the LiNi_1/3Co_1/3Mn_1/3O₂ cathode material was in good agreement with the molar ratios of the metal components in the starting solutions. The difference in chemical composition affected the rechargeable capacity and cycle stability. Li_1.2Ni_0.175Co_0.1Mn_0.525O₂ cathode material has, in comparison, high rechargeable capacity and cycle stability. The first rechargeable capacity of the Li_1.2Ni_0.175Co_0.1Mn_0.525O₂ cathode material is approximately 197 mAh/g at the rate of 1 C and its discharge capacity retention rate is 69% at the rate of 1 C after 30 cycles.

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ABSi₂O₇ is a new ferroelectric material group of which ferroelectricity has been discovered recently. In this study, we focused on potassium niobate silicate (KNbSi₂O₇), which comprises displacement-type ferroelectric substance KNbO₃ and high-covalence substance SiO₂ in the structure. KNbSi₂O₇ single crystals with a size of 10 × 10 × 1 mm³ were fabricated by the process of glass crystallization, re-melting, and slow-cooling. The polarization-electric field (P-E) curve of the KNbSi₂O₇ crystal was evaluated and KNbSi₂O₇ evidently showed ferroelectricity in the direction of c axis. The value of the spontaneous polarization was estimated to 0.11 µC/cm². The dielectric permittivity was approximately 15 for both a and c axes at 1 MHz, and this material was found to be a ferroelectric material with low dielectric permittivity.

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We studied photocatalytic activity of highly porous nanotubular TiO₂ films modified with nanoclusters of ubiquitous metal (Ti, Al, Zn, Sn, Cu, W) oxides prepared by chemical bath deposition and atomic layer deposition as well as nanoclusters of metal rich suboxides and mixed titania suboxides prepared by atomic layer deposition by following decomposition of methylene blue under simulated solar light. The mixed titania suboxide clusters constructed on the surface of TiO₂ nanotubes by atomic layer deposition demonstrated significantly enhanced photocatalytic activity in comparison to the naked TiO₂ nanotubes attributed to the better absorption of visible light due to the upward shift of the valence band near the TiO₂ surface induced by the suboxide clusters that feature low valence states and metal-metal bonds.

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The effects of Bi, Li and Ti substitutions for K, Na, Li, Nb and Sb on the piezoelectric properties of (1 – x)(K_0.474Na_0.474Li_0.052)(Nb_0.948Sb_0.052)O₃–xBi_0.5Li_0.5TiO₃ [(1 – x)KNLNS–xBLT] ceramics were investigated. X-ray powder diffraction profiles indicate the formation of a morphotropic phase boundary (MPB) between the orthorhombic and tetragonal phases in the (1 – x)KNLNS–xBLT ceramics. The ratio of tetragonal to orthorhombic phase increased with x, which suggests a decrease in the orthorhombic-tetragonal phase transition temperature (T_O–T). The dielectric constant at room temperature was increased by the substitution of Bi, Li and Ti for K, Na, Li, Nb and Sb. In addition, the temperature dependence of the dielectric constant indicated a T_O–T shift from approximately 90°C to room temperature, and resulted in a piezoelectric constant of 272 pC/N for the 0.98KNLNS-0.02BLT (x = 0.02) ceramic.

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Barium titanate based semiconducting ceramics were synthesized using Ca²⁺ and La³⁺ as dopants, TiO₂, SiO₂ and MnO as sintering aids, and various firing process. The Ca²⁺ contained ceramics without impurity phases, sintered in reducing atmosphere and subsequent annealing in air, showed both the PTCR (Positive Temperature Coefficient of Resistivity) behavior and low room temperature resistivity ρ_RT 2.2 Ω cm. Based on knowledge of ionization energy and bond disassociation energy, it was cleared that Ca substitution plays an important role in lowering the ρ_RT value in the ceramics.

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The high-power piezoelectric characteristics of (Bi_0.5Na_0.5)TiO₃ (BNT)-based solid solutions at a high temperature (~130°C) were studied, by comparing them with those of hard Pb(Zr,Ti)O₃ (PZT) ceramics. The vibration velocity v_0-p of the BNT-based ceramics was stable as the temperature increased to 130°C, whereas that of the PZT-based ceramics markedly decreased with increasing temperature. It is generally known that the stability of v_0-p under high-amplitude vibration is related to mechanical losses caused by domain wall motion. Therefore, the temperature dependence of the mechanical quality factor Q_m of these ceramics was measured by electric transient response measurement. The measured Q_m values of the BNT-based ceramics were nearly constant or slightly decreased with increasing temperature, whereas Q_m for the PZT ceramic markedly decreased with increasing temperature.

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The oxygen diffusivity in BaTiO₃ thin films heteroepitaxially grown on SrTiO₃ substrates was investigated using a gas/solid exchange technique with ¹⁸O-isotope-enriched gas. Deformation of the BaTiO₃ lattice and inhibition of the oxygen diffusivity occurred simultaneously when the YSZ layer, which is assumed to be catalytic for the ¹⁸O/¹⁶O exchange reaction, was deposited on BaTiO₃. The mechanism for the reduction in oxygen diffusivity due to the YSZ cover layer is discussed in terms of residual stress in the strained BaTiO₃ layer.

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Epitaxial thin films of heavily doped perovskite manganite (La_1−xSr_xMnO₃ or LSMO with x ≥ 0.5) were successfully fabricated onto SrTiO₃(001) single crystal substrates by chemical solution deposition. The electrical resistivity and the Hall coefficient were measured from 200 to 673 K. The temperature coefficient of resistance reached a minimum at 0.6 ≤ x ≤ 0.7. A high-temperature stability test showed that the LSMO thin films could be used up to 673 K. This study has shown that LSMO thin films are good candidates as high-temperature resistive materials that can be used in SiC power electronics.

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This paper reports study of zinc (Zn)-antimony (Sb) interactions as well as oxygen defect chemistry in dense SnO₂ ceramics using secondary ion mass spectrometry (SIMS). Dense SnO₂ ceramics with ZnO and Sb₂O₅ additives with different concentration were synthesized by conventional techniques. Characterization using SIMS revealed the morphology of the SnO₂ ceramics, the concentration of Zn and Sb in SnO₂ grains, as well as segregation and secondary phase formation. The distributions of Zn and Sb were dependent on their concentrations. Oxygen diffusivity significantly decreased by the incorporation of Sb, whereas the diffusivity slightly increased with increasing Zn concentration in the SnO₂ grain. Our results show interaction of Zn, Sb, and oxygen vacancies, suggesting that incorporation of Zn into SnO₂ grains promotes Sb incorporation into the grains.

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Electrochemical properties of layer-structured H₂W₂O₇ for electrochemical capacitors were investigated in an aqueous electrolyte for the first time. H₂W₂O₇ was synthesized from Bi₂W₂O₉ by proton-exchanges with acid treatment. H₂W₂O₇ exhibited a low redox potential of about −0.3 V in a H₂SO₄ electrolyte solution. The H₂W₂O₇ electrode showed an oxidation capacity of 56 mAh g⁻¹ at a current density of 300 mA g⁻¹, which is equal to the theoretical capacity assuming that 0.5 electrons react with one tungsten ion. H₂W₂O₇ also retained 88% oxidation capacity at a high current density of 2 A g⁻¹ against that at a low current density of 300 mA g⁻¹. It is assumed that redox reaction rate mainly depends on proton diffusion in H₂W₂O₇. Moreover, this material showed excellent cycle stability over 1000 cycles without capacity loss. It is clarified that a H₂W₂O₇ electrode is a promising electrode for electrochemical capacitors featuring a high rate capability and good cycle life.

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This study elucidated the effects of coherence and chemical composition on ionic conductivity at columnar grain boundaries of 6 mol % Y₂O₃ doped ZrO₂ (YSZ) thin films. The YSZ thin films were deposited with several orientation textures on MgO (100), Al₂O₃ (102), and SiO₂-glass substrates using metal–organic chemical vapor deposition (MOCVD). Impedance measurements revealed the total ionic conductivity of the thin films. The activation energy of the ionic conduction of YSZ thin films on MgO or Al₂O₃ substrates was 90–120 kJ/mol. These films showed similar dependence that simply increased along with decreasing coherency at the columnar grain boundaries. However, that of YSZ thin films on SiO₂ glass substrate showed dependence of the coherency at the columnar grain boundaries, but the value is higher than those of the films on MgO or Al₂O₃ substrates by more than 20 kJ/mol. Structural and compositional analyses clarified that the second phase of SiO₂ is segregated at mid-gaps between columnar grain boundaries in YSZ thin films on a SiO₂ glass substrate. Results show that two factors affect ionic conductivity at the columnar grain boundaries in YSZ thin films: structural coherency and the second phase of ionic insulator.

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Anatase titanium dioxide (TiO₂) films have attracted interest as a cathode material for dye-sensitized solar cells (DSSCs). In order to improve the power conversion efficiency (PCE) of DSSCs, it is necessary to create long electron conduction paths in the film and increase both the specific surface area and light harvesting efficiency (LHE) for incident light. To achieve these, the deposition of TiO₂ composite thin films by constant current electrophoresis was attempted using colloid mixtures of two types of TiO₂ nanoparticles with different sizes and surface properties: ca. 5 nm TiO₂ nanoparticles synthesized in this study (TNPs) and commercial TiO₂ nanoparticles of ca. 20 nm (P25) size. The size of TNPs is too small for visible light wavelengths and it is difficult to deposit thick films with TNPs, so the LHE of these films is low. Various TNP:P25 ratios were investigated to enhance the LHE and PCE for DSSCs. The P25 particles form a matrix structure in the thin film, and the TNPs are incorporated into this structure and fill the spaces between adjacent P25 nanoparticles. The upper limit of film thickness achieved without the film separating from the substrate increased with the mass content of P25. The LHE of the TiO₂ composite thin films was improved and could easily be controlled by adjusting the mass ratio of TNP:P25. The optimal PCE for DSSCs was obtained using TiO₂ composite thin films deposited using a TiO₂ colloid mixture with a TNP:P25 mass ratio of 2:7.

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(K_0.5(1+x)Bi_0.5)Bi₄Ti₄O₁₅ [KBT-10000x, 10000x = (−200)–7] were prepared by the conventional ceramic fabrication process using the KHCO₃ powder as the starting material. KBT-0 ceramic indicated high density ratio of higher than 95% and high resistivity of approximately 10¹² Ω·cm. A remanent polarization P_r, and coercive field E_c, are 10.4 µC/cm² and 70.8 kV/cm, respectively. Additionally, a high relative density ratio and resistivity exceeding 97% and approximately 10¹⁴ Ω·cm were obtained in K-poor KBT-(−100) ceramics derived from KHCO₃. This ceramic also indicated good ferroelectric and piezoelectric properties such as P_r of 12.6 µC/cm², piezoelectric constant d₃₃ of 16.0 pC/N and the mechanical quality factor Q_m of 2366, respectively.

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We attempted to fabricate metal/dielectrics composite capacitors exhibiting high effective dielectric constant by a low-temperature wet chemical approach. The green compacts consisting of Ti metal particles, BaTiO₃ fillers, and TiO₂ precursor nanoparticles were successfully converted into Ti/BaTiO₃ composite compacts by the hydrothermal method at 160°C. The effective dielectric constant of these composites tends to increase with the Ti metal content and jumped up to over 10³ near the percolation threshold. When we used the Ti(core)–BaTiO₃(shell) particles as the metal component, the thin BaTiO₃ shell layers covering on the Ti particles prevented the direct contact among metal particles and increases the percolation threshold. Since the effective dielectric constant of these composites depends largely on the dielectric properties of the BaTiO₃ layers, it is important to control the microstructure of these composites to improve the dielectric properties of such composites.

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Eu²⁺-activated Rb–Ba–Sc–Si–O glass phosphor was synthesized by a melt synthesis technique using arc-imaging furnace and their photoluminescence properties were characterized. In addition, the obtained glass phosphors annealed in a flow of 5%H₂–95%Ar gas to enhance the luminescent efficiency. The emission spectra of the Eu²⁺-activated glass phosphors presents yellow emission band centered at 537 nm due to the 4f⁶5d¹ → 4f⁷ transition of Eu²⁺, and the emission intensity was effectively enhanced by the annealing treatment.

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We have developed a low-temperature, high-magnetic-field scanning tunneling microscope combined with pulsed laser deposition. This system enables us to study atomic-scale growth of oxide thin films. In this paper, we investigated growth-mode-controlled epitaxial SrTiO₃ (STO) and LaAlO₃ films on STO(001) single-crystal substrates. A (√13×√13)-R33.7° STO(001) substrate, prepared in oxygen atmosphere, is atomically resolved and plays a crucial role in elucidating the initial growth process. Atomic-scale microscopic approach performed in this study opens up a way to novel functionalities in oxide thin films and heterostructures.

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Two-step sintering method has been applied to (Li_0.06Na_0.47K_0.47)NbO₃ (LNKN) ceramics in order to obtain a homogenous microstructure and high density (96.1% TD). The effects of the sintering temperature on the microstructure and electrical properties of LNKN ceramics were investigated. The two-step sintering has provided better densification at relatively lower temperature (≦950°C) than that of one-step sintering (1082°C), which suppresses the abnormal grain growth. In addition, the more homogeneous microstructure has been obtained by two-step sintering. The measured dielectric constant, dielectric loss and Curie temperature of the sample for two-step sintering were 666, 2.0% and 454°C, respectively, similar to the values obtained with one-step sintering. Nevertheless, LNKN ceramics prepared by two-step sintering showed higher coercive electric field (=18.8 kV/cm) than that revealed by one-step sintering (=13.0 kV/cm).

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Perovskite single-phase ceramics of Mn-doped (1 − x)BiFeO₃–xBaTiO₃ with a wide range of composition (x = 0–1.0) were prepared using the solid-state reaction. Remanent polarization P_r, was observed for (1 − x)BiFeO₃–xBaTiO₃ (x = 0.15–1.0) and remanent magnetization M_r, was observed for (1 − x)BiFeO₃–xBaTiO₃ (x = 0.15–0.8). The maximum value of P_r = 39 µC/cm² was obtained at x = 0.33 with a high Curie temperature T_C, of 420°C. The maximum value of M_r = 0.18 emu/g was obtained at x = 0.33 with a high magnetic Curie temperature T_CM, of 360°C. A multiferroic phase diagram is constructed from the T_C and T_CM observed for the samples. A multiferroic state is maintained to a high temperature up to 250°C in the wide range of x = 0.15–0.55.

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We investigated defect formation energetics at the grain boundary (GB) in CuInSe₂ (CIS) using first-principles calculations. We focused on the (112)[110] ∑3 twin GB in CIS because this GB is known to be easily formed in CIS. Formation energies and accompanied atomic relaxation of neutral Cu, In, and Se vacancies (V_Cu⁰, V_In⁰, and V_Se⁰), the In antisite defect (In_Cu⁰), and the Schottky defect (In_Cu²⁺ + 2V_Cu⁻) were investigated in the bulk and GB. We found that CIS shows characteristic atomic relaxation after vacancy formation, and V_Cu⁰ is the most energetically favorable defect in both the bulk and the GB. Furthermore, we found that (112)[110] ∑3 twin GB does not promote the formation of the Cu vacancy under all conditions, whereas it relatively promotes the formation of the Se vacancy under metal-rich conditions.

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A fluoride electrode material for lithium-ion batteries, FeF₃, was synthesized by a novel solid-state reaction method using polytetrafluoroethylene (PTFE) as a fluoride source instead of HF. FeF₃ was obtained as the main phase according to the XRD patterns of the samples prepared in the present study. Furthermore, the synthesized FeF₃ particles were nanosize. The initial discharge and charge capacities of the FeF₃ sample were 387 and 293 mAh/g, respectively, in the 4.5–1.0 V region.

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We proposed a thin-film capacitor with a stable temperature coefficient of capacitance (TCC) based on bismuth layer-structured dielectrics, CaBi₄Ti₄O₁₅. Two types of doping were conducted to lower the dielectric loss in a higher temperature range above 300°C, i.e., Mn ion to compensate for lattice defects in crystalline grains and Bi₁₂SiO₂₀ to form a grain boundary phase were attempted in order to improve the insulating property of the oriented CaBi₄Ti₄O₁₅ films. (00l) one-axis oriented Mn-doped or Bi₁₂SiO₂₀-doped CaBi₄Ti₄O₁₅ films (with Mn or Bi₁₂SiO₂₀ content up to 3.0 or 1.75%) were fabricated successfully on (111)Pt/TiO₂/(100)Si substrates buffered by (001)Ca₂Nb₃O₁₀ nanosheets. These films exhibited a relatively lower loss factor in the temperature range from R.T. up to 400°C. In particular, the behavior of TCC on the Bi₁₂SiO₂₀-doped CaBi₄Ti₄O₁₅ film was significantly stable, with a change in capacitance, ΔC/C_R.T., within ±10% even at 400°C.

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Na_2/3Fe_1/3Mn_2/3O₂ precursor powders were successfully prepared by spray pyrolysis process. Na_2/3Fe_1/3Mn_2/3O₂ precursor powders were calcined from 700 to 1100°C. The chemical and physical properties of Na_2/3Fe_1/3Mn_2/3O₂ precursor powders and the calcined powders were characterized by powder X-ray diffraction (XRD) and a scanning electron microscope (SEM). XRD revealed that the diffraction patterns of the calcined powders were in agreement with the layered structure. The crystal phases of the calcined powders obtained from 800 to 1100°C were the phase of P2 structure (space group: P6₃/mmc). Na_2/3Fe_1/3Mn_2/3O₂ precursor powders exhibited spherical morphology with 1 µm and were nonaggregated. The morphology of Na_2/3Fe_1/3Mn_2/3O₂ precursor powders changed to irregularly morphology with 1.5 µm by calcining at 900°C. P2-Na_2/3Fe_1/3Mn_2/3O₂ cathode materials calcined at 900°C exhibited high rechargeable capacity and cycle stability. The first discharge capacity of P2-Na_2/3Fe_1/3Mn_2/3O₂ cathode materials was approximately 150 mAh g⁻¹ at a rate of 0.1 C. 93% of the initial discharge capacity was maintained after 20 cycles.

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We synthesized micrometer-sized ZnO spherical particles solvothermally from the solutions of zinc acetate anhydride, hexamethylenetetramine (HMT), ethylene glycol (EG) and water, and examined the gas sensing properties. The spherical powders were composed of nano particles, which were radially aligned along the c-axis. We obtained particles with smaller crystallites under conditions of higher EG concentrations and shorter reaction period. Spherical powder made of crystallites of 3–5 nm was precipitated in the 95 vol %-EG solvent by heating at 120°C for 4 h. The ZnO powder annealed at 450°C worked as a gas sensor device for volatile organic compounds (VOC) gases. The sensitivity was the best in the case of ethanol gas at 350°C.

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We have developed an LTCC (Low Temperature Co-fired Ceramics) material, which consists of Mg₂SiO₄, SrTiO₃ and highly crystallized Li–Mg–Zn–B–Si–O glass. The material was able to be co-fired with inner cupper electrodes that have high electric conductivity. The dielectric constant is 8.8 and its Q value is 1620 at 25 GHz. Moreover, its temperature coefficient of dielectric constant τ_ε is +16 ppm/°C, which is much smaller than that of the LTCC material reported previously. Using the new LTCC material, band-pass filter (BPF) was successfully fabricated. The BPF had no defects such as delamination or cracks, and its filter properties were confirmed.

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This study is the experiments on the synthesis of Tungsten intermetallic compound (WSi₂, W₂B) by self propagating high-temperature synthesis (SHS) from two aluminothermic reactant mixture systems of WO₃–Si–Al and WO₃–B₂O₃–Al. The reactions were carried out in a SHS reactor under static argon gas at the pressure of 0.5 MPa. The standard Gibbs energy minimization method was used to calculate the equilibrium composition of the reacting species. The as-SHS products were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM) with energy dispersive X-ray (EDX) technique.

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Reaction sintered Si/SiC composite was fabricated to apply to a solar absorber and the fabricated material was evaluated on its basic properties and performance. SiC and carbon black were mixed to shape a honeycomb with a multi-channel via vacuum extrusion process. The Si/SiC honeycomb material was also fabricated with less than 5% of pores by molten silicon infiltration in vacuum. The sintered density and porosity of the fabricated material, and the 3-point bending strength at room temperature and high temperature (1100–1300°C) were measured and the thermal conductivity at room temperature and 1100°C were also analyzed. In addition, the fabricated honeycomb material was modulized and installed to a solar absorber system to measure the outlet air temperature and thermal efficiency and evaluate the performance of honeycomb material as a solar absorber material.

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Two new pentavalent bismuthates, CaBi₂O_6−x·1.1H₂O and PbBi₂O_6−x·H₂O were prepared from NaBiO₃·nH₂O. Broadened X-ray powder diffraction patterns for both bismuthates were indexed to the hexagonal cell observed for PbSb₂O₆-type SrBi₂O₆. The lattice parameters were a = 0.555(1) and c = 0.530(1) nm for CaBi₂O_6−x·1.1H₂O and a = 0.5544(4) and c = 0.531(1) nm for PbBi₂O_6−x·H₂O. At elevated temperatures, the Ca derivative decomposed to Ca₃Bi₈O₁₅ and an unknown phase via the fluorite-type structure, whereas the Pb derivative changed to Pb_1/3Bi_2/3O_4/3 via the fluorite-type (Pb_1/3Bi_2/3)O_1.4. Both Ca and Pb derivatives exhibited photocatalytic activity for the decomposition of phenol under visible light irradiation, although the adsorption of phenol was observed under dark conditions. The fluorite-type phases evolved from the Ca and Pb derivatives did not adsorb phenol under dark conditions, and their photocatalytic activities toward phenol decomposition under visible light were inferior to those of the parent compounds.

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We investigated the self-cleaning efficiencies of titanium dioxide (TiO₂) surface under ultraviolet (UV) irradiation in combination with a water flow (UV/water) condition using oleic acid as the model surface contaminant. UV light intensities were varied from a typical indoor intensity level to a representative outdoor intensity level in Japan. The combined UV/water treatment exhibited a much higher self-cleaning efficiency than either condition alone. This suggests that the self-cleaning effect occurred at nanometer-sized photo-induced superhydrophilic domains of the TiO₂ film surface located at the interface of the TiO₂ surface, oleic acid, and air.

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ZrB₂–SiC and ZrC–SiC composites were fabricated by spark plasma sintering at 1800°C for 5 min under a pressure of 40 MPa with ZrB₂ powder, ZrC powder and SiC powder as the starting materials, respectively. The phase compositions, microstructures, and mechanical properties were investigated. The results show ZrB₂–SiC composite is denser than ZrC–SiC composite. The relative density, an apparent porosity, and the bending strength of ZrB₂–SiC composite are 97.9%, 1.08%, and 310 MPa, respectively, whereas those of ZrC–SiC composite are 89.7%, 1.20%, and 257 MPa.

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The effect of firing atmosphere on the oxidation states of Fe in Arita celadon glaze and the glaze color was examined by using Mössbauer spectroscopy. The celadon glaze was prepared from feldspar, BaCO₃, kaolin, α-quartz, and Fe₂O₃ powders and fired on the white porcelain biscuit plate at 1300°C for 0.5 h under several reduction atmospheres. The content of Fe₂O₃ in the glaze was 2 mass %. In oxygen atmosphere, the color of celadon glaze was gray-yellow due to Fe³⁺. The color of the celadon glaze changed from gray-yellow to blue-green with increase of CO concentration in the atmosphere. With the increase CO concentration, Fe²⁺ increased and the concentrations of Fe²⁺ were 85.9% at 0.5%CO and 95.6% at 1%CO, respectively. At 4% CO, iron state was only Fe²⁺.

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