In this review, following two topics are introduced: 1) experimental and theoretical electron energy loss (EEL) near edge structures (ELNES) and X-ray absorption near edge structures (XANES), and 2) atomic and electronic structure analysis of ceramic interface by combing spectroscopy, microscopy, and first principles calculation. In the ELNES/XANES calculation, it is concluded that inclusion of core-hole effect in the calculation is essential. By combining high energy resolution observation and theoretical calculation, detailed analysis of the electronic structure is achieved. In addition, overlap population (OP) diagram is used to interpret the spectrum. In the case of AlN, sharp and intense first peak of N-K edge is found to reflect narrow dispersion of the conduction band bottom. By applying ELNES and the OP diagram to Cu/Al₂O₃ heterointerface, it is revealed that intensity of prepeak in O-K edge is inverse proportional to interface strength. The relationships between atomic structure and defect energetics at SrTiO₃ grain boundary are also investigated, and reveal that the formation behavior of Ti vacancy is sensitive to the structural distortion. In addition, by using state-of-the-art spectroscopy, microscopy, and first principles calculations, atomic scale visualization of fluorine dopant in LaFeOAs and first principles calculation of HfO₂ phase transformation are demonstrated.

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Titania is a very important material for various applications and its properties are expected to be improved by controlling the crystallographic orientation. In this study, we demonstrated that the c-axes of both rutile and anatase were aligned parallel to a magnetic field and we investigated the effect of the orientation on the microstructure development and the effect of the transformation from anatase to rutile on the orientation during heating. When using rutile as the starting material, the c-axis was aligned and the elongated grains were aligned after sintering. When using anatase as the starting material, the c-axis of anatase was aligned parallel to the magnetic field. However, after transformation, the rutile had a tilt and the anisotropic grain growth was suppressed.

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We have investigated the influence of 38 kinds of metal ions on photochromism in BaMgSiO₄ (BMS). We have found that the doped Fe ions are the most effective to enhance the photochromism. The Fe-doped BMS shows great sensitivity to blue light (wavelength λ = 405 nm) and turns bright pink. The colored Fe-doped BMS is bleached by green light (λ = 532 nm) irradiation. The coloration-bleaching process is repeatable. The color density of the photochromism depends on the wavelength of irradiation lights. We think that the photochromism enhancement is due to the electron deeper traps formed by the doped Fe ions.

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The hybridization of polyaniline (PANI) and TiO₂ leads to unique materials, which exhibit the enhancement of photocatalytic properties. Further improvement requires high dispersion state of TiO₂ in the hybrid. In this study, highly dispersed PANI nanofiber/TiO₂ nanoparticles hybrids were obtained by modifying the surface charge of TiO₂ nanoparticles via layer by layer (LbL) technique. The structural studies of the hybrids confirmed the presence of PANI along with anatase TiO₂ nanoparticles. The degradation of methylene blue (MB) in an aqueous solution under visible light irradiation was carried out to study the photocatalytic activity of the hybrids. The hybridization of PANI nanofiber and TiO₂ nanoparticles resulted in an enhancement of photocatalytic activity for visible light.

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A sol of Mn²⁺-doped ZnS nanoparticles was prepared by heating a ZnS precipitate with Mn²⁺ ions in ethylene glycol at 348 K for 24 h. The precipitate was prepared by mixing the aqueous solution of Zn(NO₃)₂·6H₂O and Mn(NO₃)₂·6H₂O with an aqueous solution of Na₂S According to the UV–VIS absorption spectra, when the wavelength was more than 400 nm, the optical absorptions of the obtained sols with the molar fraction of Mn²⁺ ions in the solution (X_Solution: the molar fraction of Mn²⁺/(Mn²⁺ + Zn²⁺) in the aqueous solution) less than 0.02 were less than 0.12 and the obtained sols were clear and transparent for the visible light. The sol of Mn²⁺-doped ZnS nanoparticles showed PL characteristics when irradiated with an excitation light with a wavelength of 345 nm. Accordingly, a simple process to heat the mixture of the sulfide precipitate and ethylene glycol at 348 K enabled us to obtain a homogeneous transparent sol of Mn²⁺-doped ZnS nanoparticles with PL characteristics. According to the results of the chemical analysis of the molar fraction of Mn²⁺ in the obtained precipitate (X_Precipitate) and the nanoparticles in the sols (X_Nano), the X_Nano was less than that the X_Precipitate as compared with the same X_Solution. The Mn²⁺ ions in the nanoparticles were dissolved in the solvent during the heat treatment since the solubility product of MnS was much larger than that of ZnS. As such, the dissolution-precipitate process played an important role in the formation of the sol.

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Nanosized δ-alumina (δ-Al₂O₃) powders were calcined at various temperatures under a flow of ammonia (NH₃) passing over a carbon black-containing crucible. The nitridation process of δ-Al₂O₃ to aluminum nitride (AlN) was monitored by powder X-ray diffraction, infrared (IR) spectroscopy, and ²⁷Al magic-angle spinning nuclear magnetic resonance spectroscopy. δ-Al₂O₃ began to be converted to AlN at 1150°C without δ-α alumina transformation and the conversion was completed at 1300°C for 5 h. The IR spectra of the gases evolved during the nitridation revealed the inclusion of NH₃, CH₄, HCN, and CO gases. Results on the calcination of δ-Al₂O₃ under a flow of acetonitrile diluted in argon indicated that HCN is involved in the nitridation reaction of δ-Al₂O₃.

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Potassium sodium niobate (KNN) is a well known piezoelectric material and a developing candidate for replacing lead based high performance piezoceramics due to limitations of hazardous materials in electronic devices. Lithium substitution in KNN structure leads a crystal transition from orthorhombic to tetragonal symmetry at room temperature and enhances ferroelectric properties. In this study, lithium substituted KNN piezoceramics with high relative densities were prepared by spark plasma sintering (SPS). Densification, crystal structure, microstructure and ferroelectric behavior of the samples were investigated. It was observed that lithium niobate based secondary phases exist in sintered KNN ceramics. These secondary phases showed significant effects on ferroelectric properties. Maximum (P_m) and remnant (P_r) polarizations were determined as 27 and 20 µC/cm², respectively for pure KNN at the electric field of 20 kV/cm. When the electric field was increased to 30 kV/cm, P_m did not change significantly, but remained below P_r. For Li substituted samples, P_r decreased with increasing Li content.

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Fine-structured β-SiC ceramic patterns were successfully fabricated from a facile replication route using Si mold as the master structure, PVA as the binding agent and nanosized β-SiC powder as the raw material. After slurry deposition and drying, the patterns were integrally transferred from the Si mold to the coating samples. The intact micropatterns were maintained up to 1500°C without obvious shrinkage. The samples exhibit nearly net-sized feature of 1.7 µm after drying and sintering. This net-sized structure is a great advantage of β-SiC patterns over the counterparts of oxide ceramic materials. All samples are in nanosized porous structure with narrowly distributed pore sizes.

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Porous mullite-bonded silicon carbide (SiC) ceramics were prepared from SiC and aluminum hydroxide [Al(OH)₃] powders. The Al(OH)₃ content was varied from 14.5 to 47.3 wt %, and porous SiC ceramics were fabricated via reaction sintering at 1450–1550°C for 2 h. The microstructure showed large SiC grains embedded in a matrix of small and loosely packed mullite/alumina particles. It was demonstrated that the porosity decreased and flexural strength increased with increase in Al(OH)₃ content. The porosity varied from 46 to 54%, and flexural strength varied from 3 to 14 MPa with the variation in Al(OH)₃ content and sintering temperature. Typically, porous mullite-bonded SiC ceramics of 14 MPa strength and 47% porosity were obtained when SiC and 47.3 wt % Al(OH)₃ powders were sintered at 1500°C.

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Local structural disorder of perovskite oxynitrides BaTaO₂N and BaNbO₂N is investigated by constant-wavelength neutron powder diffraction measurements at 300 and 6 K. Temperature-dependent diffraction line-broadening analyses together with the Rietveld refinements confirm that both perovskites retain average structures of simple cubic symmetry down to 6 K. While the Ta and Nb atoms in the above oxynitrides have remarkably large displacement parameters, indicative of pronounced octahedral distortions, the rigidity of Ba sublattice seems to suppress the cooperative propagation of long-range octahedral tilting.

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Slurries of quartz and slaked lime containing various crystal phases of alumina were hydrothermally reacted to synthesize aluminum-substituted tobermorite. X-ray diffraction results confirmed the formation of aluminum-substituted tobermorite during the reaction. The aluminum species were substituted at the Q² or Q³ sites in tobermorite. The amount of aluminum substituted in the tobermorite depended on the reactivity of alumina. The tobermorite formed showed fiber- and plate-like morphologies. The reactivity of the alumina used as an additive influenced the substitution site and the amount of aluminum substituted into the tobermorite structure, resulting in controlling its morphology.

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This paper describes a novel experiment on surface modification for alumina plates. Polycarbosilane (PCS), an organosilicon polymer, was used in this experiment as a precursor. Tiny cracks on an alumina surface caused by grain boundaries and introduced by rough grinding were filled by PCS, and PCS was transformed into silicon oxycarbide (SiCO, silicon carbide including several mass percents of oxygen) by thermal oxidation curing at 453 K and pyrolysis at 1273 K. Moreover, Al₆Si₂O₁₃ (mullite) layer was made from alumina and SiCO and prevented exfoliation of the alumina and SiCO during pyrolysis. In addition, the wettability between samples and molten aluminum was investigated in order to make sure the effect of surface modification. This experiment confirms that surface modification of alumina with a SiCO membrane can be successfully.

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We have developed a centrifugal heating apparatus to fabricate layered TiS₂-based thermoelectric elements, and evaluated their thermoelectric properties. We found that layered (SnS)_1.2(TiS₂)₂ bulk elements with preferred crystallographic orientation can be produced within a quartz tube under a centrifugal acceleration of 1,000 g or higher and at a maximum temperature of 1,073 K or higher. With the increasing centrifugal acceleration from 1,000 to 8,000 g, the electrical conductivity of the produced specimen was almost doubled possibly because of the increased degree of crystal-axis orientation. For the specimens produced at 8,000 g, we estimated a maximum thermoelectric figure of merit, ZT, of approximately 0.2 (673 K). We have thus demonstrated that it is possible to use the centrifugal heating technique to fabricate layered TiS₂-based thermoelectric elements directly from the powdered raw materials.

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