Understanding the reaction processes that can affect crystal structure and thermodynamics is important to improve the characteristics of highly functional oxides. During the charge–discharge processes of lithium-ion battery cathode materials, structural changes that accompany lithium intercalation and deintercalation are important factors that govern the characteristics. An original thermodynamic analysis of these processes was adopted and structural analysis using neutron diffraction during the charge–discharge process was successfully conducted for the first time to identify the structural changes in a coin cell-sized cathode. Structural analysis also employed quantum beams (neutron, synchrotron radiation), and the bonding characteristics were investigated with the maximum entropy method (MEM) by determination of the electron density distribution. Moreover, a pioneering application of the crystal pair distribution function (PDF) analysis for the bulk material together with X-ray absorption fine structure (XAFS) analysis enabled examination of the local structural changes that average structural analyses could not reveal. The diversified approach of this research involved a combination of these methods. Consequently, the structural and thermodynamic stability were determined to be important for improvement of the characteristics of highly functional oxides.

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Recent investigations on the quadruple perovskite series, ACu₃Fe₄O₁₂ (A = divalent alkaline-earth metal or trivalent rare-earth metal ion), have demonstrated anomalous electronic phase transformations such as charge disproportionation and charge transfer. These behaviors originate from the unusual high valence Fe⁴⁺ (or Fe^3.75+) ions that are dominated by ligand holes. In this review, various structural transformations and electronic properties in ACu₃Fe₄O₁₂ perovskites are shown. Furthermore, intriguing structure–property relationships of the A³⁺Cu₃Fe₄O₁₂ perovskites are presented. The local structural distortions on metal-oxygen bonds, which are represented as bond discrepancies and global instability indices, are closely related to the electronic phase transformations at low temperature generating a wide range of remarkable phenomena such as negative thermal expansion, ferromagnetism, and metal–nonmetal transitions.

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In this review, we have presented several techniques to tune the luminescence both spectrally and spatially by coupling the emission centers to metallic nanostructures, with an emphasis on our works. Metallic nanostructures include single, couples of, and arrays of nanoparticles. Especially the periodic array of the nanoparticles not only can modify the emission spectra, but also select the emission directionality out of the structure. These techniques may find application in the fields of illumination and sensing.

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Novel potentials of calcium silicate ceramics for environment-friendly material applications are briefly described based on experimental and computational simulation methods. Calcium phosphate clusters were successfully incorporated into the structure of tobermorite under hydrothermal reaction conditions. The incorporation of the cluster resulted in changes in the crystal structure and density of states of tobermorite, thereby improving the biocompatibility of the resulting material. The chemical composition of the hydrogarnet could be controlled using a potassium solution during hydrothermal reaction in a CaO–SiO₂–Al₂O₃–H₂O system. This afforded tailoring of the content of the surface hydroxyl groups. Consequently, this led to enhanced adsorption abilities towards organic compounds in solution.

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In order to improve the matrix microstructure of SiC-fiber-reinforced SiC matrix (SiC/SiC) composite, the authors examined a combination process involving the polymer impregnation and pyrolysis (PIP) process and a pore-producing treatment that incorporates a pore-forming agent into the matrix precursor. Unidirectional SiC/SiC composites were fabricated under such conditions of selected slurry preparation that a good porous monolith could be obtained. A porous matrix base was formed relatively uniformly in both the intra- and the inter-bundle region in the first PIP processing, and subsequently densified efficiently by repetitive process cycles of PIP. By comparing the resulting composites with those fabricated via the conventional PIP process, it was verified that this newly attempted fabrication process is advantageous in lowering the porosity, particularly by reducing the size of the intra-bundle pores, and leads to an improvement in some representative mechanical properties.

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The effects of aluminum compound additive on the thermoelectric properties of α-SiC ceramics were studied. Porous SiC ceramics with 50–60% relative density were fabricated by sintering the pressed α-SiC powder compacts with AlN and/or Al₄C₃ at 2150°C for 3 h in Ar atmosphere. The sintered bodies were analyzed by means of XRD, SEM, and TEM. The lattice parameter measurements revealed incorporation of a certain amount of added Al and/or N into the SiC lattice. 6H to 4H reverse phase transformation occurred during sintering. The Seebeck coefficient, electrical conductivity and thermal conductivity were measured at 550–950°C in Ar and/or vacuum atmosphere. The kind of additives and the amount of addition had significant effects on the thermoelectric properties. The thermoelectric figure of merit of aluminum compound-doped SiC increased with increasing temperature and was lower than that of n-type SiC. On the whole, AlN-doped SiC had higher figure of merit than Al₄C₃-doped SiC.

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Electrophoretic deposition (EPD) has attracted attention as a coating technology for ceramic particles. Ethyl perfluorobutyl ether (EFE), a hydrofluoroether, can be used as a solvent for preparing silica particle suspensions for EPD. EFE is polar, nonflammable, and has a high density. In addition, the electrical insulation of EFE allows significant power savings over conventional EPD. In this study, the power consumption of EPD with EFE was compared with that of EPD with various common solvents. The silica particle suspension showed a high zeta potential in EFE. Power consumption per unit deposition amount in EFE at 10 V was 6.4 × 10⁻⁵% of that of water at 100 V. Similarly, it was 2.6 × 10⁻³% of that of acetone, 7.8 × 10⁻⁵% of that of ethanol, and 7.5 × 10⁻⁵% of that of ethanol at 100 V. Compared with the solvents used previously in EPD, EFE offers significant energy savings to the EPD process.

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Ni-Carbon nanotube (CNT)-Ni_0.5Zn_0.5Fe₂O₄ multiphase composites were successfully prepared using microwave sintering (MWS) and spark plasma sintering (SPS) techniques. The obtained samples were characterized by scanning electron microscopy, electrical conductivity, and physical properties measurement system with vibrating sample magnetometer. The SPS prepared composites exhibited higher density, fine grain size, and to maintain favorable three-dimensional conductive network of CNTs compared with the microwave sintered (MWS) ones. Whether use MWS or SPS, both the density and the grain size are increasing with the CNT content increment. The increasing of density and grain size is the main contribution of the saturation magnetization increasing. In the composites of high content of CNTs (such as 5 wt %), the spinel structure of ferrite was totally destroyed, as indicated by a considerable decrease in the saturation magnetization. Interestingly, it is found that the Curie temperature increases with the increment of CNT content while the high saturation magnetization was maintained, which has implication that the multiphase ferrite composites will find application in a broad temperature range.

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The benefits of branched TiO₂ nanotubes in comparison their non-branched counterparts with respect to dye sensitized solar cells (DSSC) were studied. The branched nanotubes were produced by ramping the applied voltage during anodization by a factor 1/√2. DSSC performance, dye loading, and the impedance of the oxides were investigated. It was found that dye absorption of the branched nanotubes is lower than non-branched ones; however, in contrast, improvements in DSSC performance were obtained. The resistance of the branched nanotubes showed a significant decrease, considered to be caused by the branched nanotubes providing a greater amount of pathways for electrons to be transport along. This decrease could be considered to be a factor the improved DSSC performance.

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The reaction behavior of chemically vapor-deposited BN ceramics in wet air was investigated. The results showed that the oxidation reaction occurred simultaneously with the volatile reaction. The long-term degradation rate of BN was determined by the volatilization reaction of B₂O₃ with H₂O. The reaction kinetics was discussed using different kinetic models, i.e. the paralinear kinetic model and RPP model. Although both models could be adopted to fit the experimental data, RPP model was preferred because the model not only gave an explicit expression of the reaction fraction as the function of all parameters that would be convenient for theoretical discussion, but also it would perform a simple calculation.

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The luminescence properties related to the thermal polymer/ceramic conversion behavior of silicon dicarbodiimide {SDC, [Si(N=C=N)₂]_n} have been investigated. SDC was synthesized by the non-oxidic sol–gel condensation reaction of silicon tetrachloride with bis(trimethylsilyl)carbodiimide. As-synthesized SDC showed no luminescence under UV light, while heat-treated SDC showed an appreciable photoluminescence (PL) and the maximum visible PL emission intensity was achieved by heat treatment at 400°C. Even after the heat treatment up to 970°C, the SDC preserved most of the N=C=N groups to keep whitish gray color without distinct free carbon formation, and emitted visible blue luminescence. The 400°C-heat treated SDC exhibited the intense luminescence excited at 281 and 379 nm wavelengths, while there was no PL emission excited by the N=C=N group-derived host absorption at 214 nm. The PL properties of the heat-treated SDCs could be correlated with their preservation of the local structure including N=C=N groups and defects formation during the heat treatment. Moreover, Eu³⁺-modified SDC was prepared by the same sol–gel method using Eu(III) chloride as the Eu³⁺-source. The results of FT-IR and ²⁹Si NMR spectroscopic analyses revealed a complex formation between the Eu(III) chloride and bis(trimethylsilyl)carbodiimide. As a result, the Eu³⁺-modified SDC exhibited a characteristic PL red emission at around 600 nm attributed to the f-f-transition of Eu³⁺.

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The cation-ordered α-PbO₂-related Sn^IV_0.82(Ta_0.94Sn^IV_0.06)O_4.11 phase, which is a triclinic or monoclinic system with lattice parameters of a = 0.769 nm, b = 0.947 nm, c = 0.769 nm, α = 90°, β = 96.34° and γ = 90°, was synthesized by annealing of the cation-ordered fluorite-related Sn^IV_0.82(Ta_0.94Sn^IV_0.06)O_4.11 phase at 973 ≤ T ≤ 1073 K in O₂; the cation-ordered fluorite-related phase was prepared by the oxidation of the Sn^II_1.64(Ta_1.88Sn^IV_0.12)O_6.58 pyrochlore. The Sn^IV and [0.94Ta + 0.06Sn^IV] were respectively ordered similar to that of Sn^II and [0.94Ta + 0.06Sn^IV] as observed in the precursor pyrochlore phase. The superlattice diffraction due to the cation-ordering did not appear in its XRD because of the high density of the anti-phase domain boundaries parallel to {101} direction. The transformation temperature from the fluorite-related form to the α-PbO₂-related form for the Sn^IV_0.82(Ta_0.94Sn^IV_0.06)O_4.11 was approximately 250 K higher than that observed for the previous Sn^IV_0.81(Nb_0.93Sn^IV_0.07)O_4.085. The difference in the transformation behavior starting from the precursor pyrochlore phase between the present Sn–Ta–O and the previous Sn–Nb–O systems was discussed on the basis of the characteristics of the Ta- and Nb-ions.

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W_xZn_1−xO films with various doping concentration were prepared using pulsed laser deposition (PLD) on the (1120) face of sapphire. The c-axis-oriented W_xZn_1−xO films were grown without in-plane rotation domains when the W content in the films was below 3.6 at.%. The films exhibit a high transmittance of approximately 80% in the visible-near infrared region regardless of the W content, and no shift of the absorption edge was observed. From the results of Hall measurements, it was revealed that the doping efficiency of W in the films was <0.15 electrons/W. The electron mobility of the W_xZn_1−xO films was 14–35 cm² V⁻¹ s⁻¹, which is relatively low compared with that of the undoped ZnO film grown using PLD. The low doping efficiency and electron mobility are considered to be attributed to the formation of defects resulting from the W-doping.

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Silicon nitride ceramics were fabricated via 2.45 GHz microwave sintering at different systems which included Si₃N₄–Y₂O₃–Al₂O₃ system, Si₃N₄–Y₂O₃–Al₂O₃–ZrO₂ system and Si₃N₄–Y₂O₃–Al₂O₃–ZrO₂–Li₂CO₃ system. The system of Si₃N₄–Y₂O₃–Al₂O₃–ZrO₂–Li₂CO₃ exhibited preferable properties which had completely phase transformation, Vickers hardness of 12 GPa and the flexure strength of 400 MPa at a lower temperature of 1550°C. The results also showed that ZrO₂ had good ability in absorbing microwave and Li₂CO₃ could promote the densification. Scanning microscopy micrographs revealed the phenomenon of crack deflection, debonding and pull-out of β-Si₃N₄ grains.

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Formation of bismuth nano-particles by polyol process have been studied in terms of the effect of additives on its size and shape. Bismuth trichloride solved in ethylene glycol was reduced at high temperature with the existence of poly(vinylpyrrolidone) (PVP) and ferric chloride. Spherical particles were mostly formed with the solitary addition of PVP. Sphere size was decreased from 400 to 200 nm with increasing amount of the PVP. Addition of larger weight-average molecular weight (M_w) of the PVP decreased the sphere size slightly. On the other hand, hexagonal or rectangular plate-like particles were obtained at a high number ratio over 70% by the co-addition of ferric chloride with the PVP. Plate size and the fraction of plate-like particles tended to increase slightly with the increase of amount of the PVP. The plate size also increased with increase of molecular weight of the PVP and square plate-like particles larger than 1 micrometer were obtained with the addition of the large molecular size of PVP (M_w ~1,300,000). Adequate amount and size of PVP tended to decrease totally the growth speed of particles and to suppress coalescence with each other, and ferric ions suppressed the growth speed toward the c-axis by alternative re-oxidization of bismuth metal.

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