Barium titanate (BaTiO₃) powder was synthesized using the emulsion combustion method (ECM) from a water-in-oil-type emulsion, in which a barium nitrate aqueous solution, a titania sol, kerosene and a surfactant were included, at a firing temperature of 850°C. Particle characteristics and sintering behavior of the synthesized particles were evaluated. The particles of the synthesized powder were nearly spherical in shape, 200-500nm in diameter and polycrystalline. The diameter of the particle was almost consistent with that calculated from the size of the aqueous microsphere in the emulsion, the concentration of metal ions and the density of BaTiO₃. The X-ray diffraction (XRD) pattern showed that the main product (over 95%) was BaTiO₃ and that a small amount of Ba₂TiO₄ was synthesized. The compact of the synthesized powder was densified up to 90% of the theoretical density at a sintering temperature of 1200°C, which was 100°C lower than that of the powder produced by the hydrothermal process. The fine polycrystalline structure of the ECM-made particles was considered to enhance the densification at a lower temperature. The sintered specimen showed a typical temperature dependence of dielectric constant in BaTiO₃, which included two peaks at 20 and 120°C, corresponding to orthorhombic-tetragonal and tetragonal-cubic phase transitions, respectively.

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Thermal analysis, phase and electrochemical properties of nano-LiMn₂O₄ powders synthesized at low temperature by citric acid gel process were investigated. The activation energy for LiMn₂O₄ formation was 130.8kJ/mol when lithium manganese citrate was used as a precursor. The lattice parameter and volume of LiMn₂O₄ powders increased with synthesis temperature increased, which resulted from the decreased average valence of manganese. As the temperature was above 700°C, LiMn₂O₄ underwent phase transition from a cubic to a tetragonal phase, which was attributed to oxygen removal in the lattice. In cyclic voltammogram (CV) analysis, the two pairs of oxidation and reduction CV curves indicated that, apparently, the insertion and extraction reactions of lithium ion occurred in two stages. The initial discharge capacity of LiMn₂O₄ powders increased with the increasing calcination temperature, but the powders calcined at lower temperatures exhibited a better cycling behavior than the ones calcined at higher temperatures. The capacity fading of the spinel LiMn₂O₄ was due to structural damages caused by the Jahn-Teller distortion.

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Preparation of porous microspheres in the SiO₂-ZrO₂-CaO-Na₂O system was investigated by heating a mixture of fine Na₂CO₃ powder and commercially available, microspherical silica gel impregnated with ZrOCl₂ and CaCl₂, and by subsequently washing the product with water. Porous microspheres, whose surface was composed of sponge-like skeletons were obtained; their pore volume was up to 0.59cm³·g^-1 and the mode pore radius was in the range between 23 and 38nm. The composition of the porous microspheres was SiO₂-ZrO₂-CaO-Na₂O, which contained ZrO₂ in the range between 11 and 17mass%. Almost all amounts of Ca and Zr added and a certain amount of Na remained in the porous microspheres. Addition of CaCl₂ resulted in a more homogeneous distribution of ZrO₂ and an increase in resistance to alkaline solution, compared to those of the microspheres prepared by the same procedure without CaCl₂ addition.

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Fine powders of In₂O₃ were obtained by thermal decomposition of the precipitates, which were prepared by an oxalate method in ethanol solution. The sinterability of the powders was improved considerably, compared with that of commercial powders. The maximum density reached 82% of the theoretical value by sintering at 1450°C. Furthermore, the relative density increased as high as 90.9% by a new two-step sintering process, which includes a presintering step at a relatively low temperature and a final sintering step at 1450°C under atmospheric condition. The electrical resistivity of sintered In₂O₃ was strongly dependent on the relative density and increased in proportion to the measurement temperature, showing metallic conduction behavior. The temperature coefficient (α) in the linear relationship was ascribed to an electron scattering effect due to porosities. The residual resistivity (ρ_r) of 0.0038Ω·cm, which was estimated by extrapolation to 0K, agreed with the value reported for the single crystal grown from vapor phase.

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Suspensions of Cu²⁺ adsorbed tetragonal ZrO₂ (3Y-TZ: 3mol%Y₂O₃-doped tetragonal zirconia) powder were prepared and their green bodies consolidated without powdering process by a pressure filtration method. Green bodies with a narrow pore size distribution were obtained after cold isostatic pressing of the pressure filtrated bodies. Small amounts of CuO addition resulted in lower densification temperature by the aid of a liquid phase. Bulk and grain-boundary conductivities were measured by a complex impedance method. Bulk conductivity was nearly independent of CuO addition but grain-boundary conductivity decreased with CuO addition.

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Glasses in the systems of Li₂O-SnO-B₂O₃ and Li₂O-SnO-BPO₄ were prepared by a melt quenching method and their thermal, viscous, and electrochemical properties were investigated. The SnO based glasses exhibited the relatively low glass transition temperatures (T_g) of ≈350°C and an excellent thermal stability against crystallization. The values of T_g and E_η/T_g, where E_ηis the activation energy for viscous flow at around T_g and E_η/T_g is the fragility parameter, were maximized at around a composition of 40mol% SnO in the SnO-B₂O₃ system. The electrochemical properties of those glasses were investigated by using a simple three-electrode cell with the glass as a working electrode, lithium sheets as both counter and reference electrodes, and 1M LiPF₆/EC+DEC as a liquid electrolyte. The SnO based glasses worked as anode materials with high discharge capacities over 650mAh·g^-1 at the first cycle and exhibited good cycling performance.

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Crystals of Sr₂(Si_1-xGe_x)O₄ with 0≤x≤1 were prepared and examined by powder XRD, optical microscopy, and AFM. The crystals with 0.3≤x≤0.6 were composed of both the α′ (orthorhombic)- and twinned β (monoclinic)-phases. On the basis of the lattice correspondence between the two phases and their cell parameters, the phenomenological crystallographic theory has been applied to determine the habit planes and shape deformations upon α′-to-β martensitic transformation. The habit planes, which define the coherent interphase boundaries between α′ and β, were nearly parallel to either (100) or (001). Because the transformation was accompanied by a small volumetric shrinkage of -0.3%, the parent α′-phase would elastically accommodate the strains upon the polysynthetic twin formation of the β-phase. At 293K, the crystals with x=0.6 were composed of -92.5mass%α′ and -7.5mass%β. During further cooling in liquid nitrogen, the α′-to-β transformation proceeded which increases the phase composition of β up to -56.3%. The transformation is accompanied by the formation of plate-like surface reliefs. The surface relief angles have been determined from both observations (7.4±0.2°) and calculations based on a phenomenological analysis (7.55°). The fair agreement of these values indicates that the transformation is martensitic and mainly governed by a shear mechanism. The shape memory effect has been demonstrated by the reproducibility of the surface reliefs. The coherency at the interface boundaries between the α′ and β-phases as well as the effective strain accommodation substantially account for the thermoelasticity of the solid solutions.

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The factors which influence the formation of layer structured A_nNb_n+3mO_3n+3m[(ANbO₃)_n(NbO)_3m](A=Ba, Sr), consisting of m-NbO blocks and n-ANbO₃ (perovskite type) blocks, were discussed. In the Ba_nNb_n+3mO_3n+3m system, compounds with a larger value of n/m ratio were synthesized at lower temperature than that with a smaller value of n/m ratio. Lattice constant of a-axis of these compounds decreased with increasing n/m ratio (Ba₂Nb₅O₉ (n/m=2/1) [a=0.4172nm], BaNb₄O₆ (n/m=1/1) [a=0.4182nm], BaNb₇O₉ (n/m=1/2) [a=0.4195nm]). This tendency was also the same for the Sr_nNb_n+3mO_3n+3m system (Sr₂Nb₅O₉ (n/m=2/1) [a=0.4141nm], Sr₂Nb₈O₁₂ (n/m=2/2) [a=0.4166nm]). On the other hand, when the amount of Ca substitution for Ba or Sr increased, (Ba, Ca)Nb₄O₆ (n/m=1/1) and (Sr, Ca)₂Nb₈O₁₂ (n/m=2/2) were formed instead of (A, Ca)₂Nb₅O₉ (n/m=2/1) at 1573 and 1673K, respectively. These different tendencies can be explained in terms of matching of NbO block and ANbO₃ block. Not only the difference of lattice sizes between NbO block and ANbO₃ block, but also the symmetric property in ANbO₃ block have large effects on the formation of A_nNb_n+3mO_3n+3m.

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The formation process of BaTiO₃ from powder compacts, equi-molar mixture of BaCO₃ and TiO₂, and an abnormal expansion during the formation process were investigated. Powder compacts were fired for 30min in air atmosphere at various temperatures, up to 1200°C. The formation process of BaTiO₃ is devided into three steps; firstly, BaTiO₃ is formed at the contact points between BaCO₃ and TiO₂ particles, secondly, Ba₂TiO₄ is formed by the reaction of the prior-formed BaTiO₃ with BaCO₃, finally, BaTiO₃ is formed by the reaction of residual TiO₂ and Ba₂TiO₄. In the macroscopic observation, it was confirmed that a powder compact of BaCO₃ on magnesia and rutile substrates begins to melt at 950°C. This liquid phase is thought to influence the formation reaction of BaTiO₃ greatly. It is well known that Ba component diffuses to TiO₂ one-sidedly in this reaction. As a result, the space where BaCO₃ occupied in a compact specimen remains as a pore after the termination of reactions. Then, an increase in the volume happens by TiO₂'s changing in BaTiO₃. These are considered to be the cause of an abnormal expansion caused by the reaction of BaCO₃ and TiO₂.

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High-surface-area alumina with aligned macro- and microscopic pores was synthesized by a single-step processing using freeze-drying. A water-based slurry of Al₂O₃ and Al(OH)₃ mixture was frozen while controlling the freezing direction. The frozen slurry was dried under reduced pressure and columnar pores were generated after sublimation of ice in the green body. By sintering this green body, we obtained porous alumina with a complex pore structure, where aligned macroscopic open pores contained 10nm sized pores on their internal walls. These minute pores were formed during thermal decomposition of Al(OH)₃, which consequently resulted in a high surface area.

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It is well known that cementitious materials are deteriorated by sulfate attack. Submerging tests of hardened cement paste and mortars were employed with sodium sulfate solution. The samples were prepared from ordinary portland cement and blast furnace slag cement. The test results showed that the sulfateion migration was not governed by Fick's law. In the region of sulfate ion migrated, ettringite precipitated as a secondary product and the volume of capillary pores, in diameter of 18.3-212.5nm, decreased. It was also observed that pores in diameter of 18.3-212.5nm developed at areas where sulfate ion did not migrate. This should be considered as an important feature. In addition, secondary formation of gypsum was identified in the case of blast furnace slag cement. Compressive strength test and 3-point bending test were carried out to diagnose the mechanical performance against the sulfate ion ingress. Two types of alteration model were considered to evaluate the alteration depth and degree. Each model is working for the compressive test and the bending test, individually. We have proposed new indexes with these models. These indexes describe the alteration depth and degree, and closely relate to other indexes, such as sulfate ion migration depth and so on. According to these indexes, it seems that sulfate ion migration might cause filling of pore and generating of micro defect, alternatively, and progress the deterioration. This mechanism showed good agreement with apparent phenomena such as changes in profiles of sulfate ion and in strength.

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Silicon nitride powders with concurrent addition of Yb₂O₃ and MgO were sintered at 1900°C for 2-48 h under 0.9 MPa nitrogen pressure. Microstructure, lattice oxygen content and thermal conductivity of the sintered specimens were evaluated. All specimens had a duplex microstructure composed of small matrix grains and elongated grains. Thermal conductivities of sintered bodies were remarkably increased with sintering time and reached a maximum value of about 120W·m^-1·K^-1. The lattice oxygen content of dense silicon nitride sintered body decreased with sintering time. The thermal conductivity increased with decreasing the lattice oxygen content. So far, it was reported that the thermal conductivity of Si₃N₄ was affected by grain size and morphology, composition and thickness of grain boundary layer. It was revealed that thermal conductivity of sintered specimen was closely related to the oxygen content present in the silicon nitride lattice.

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The effect of addition of binary system CaO-Y₂O₃ on the synthesis of AlN powder by carbothermal reductionnitridation of Al₂O₃ was investigated. The nitridation was conducted at 1450°C in N₂ gas flow. The morphology of synthesized powders was different from the original Al₂O₃ powder. The XRD analysis showed that the reaction progressed through formation of several aluminates during nitridation. These aluminates were confirmed to promote the nitridation and vary the morphology of raw Al₂O₃. The amount of additives remained in final product is smaller than that of starting powder. This synthesized powder is considered to be advantageous to the densification because remaining compounds can act as a sintering aid.

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A confocal scanning laser microscope (CSLM) was applied to identify the location of fracture origin in alumina ceramics. Alumina-referceram was ground to obtain JIS R-1601 specimens using a grinding machine. They were fractured in four point bending to measure strength. CSLM and scanning electron microscope (SEM) micrographs of fracture surface were compared. With a CSLM, the location of fracture origin could be easily determined, while it was very difficult with a SEM. Fracture toughness K_IC=2.3MPa·m^1/2 calculated from the measured size of fracture origin and the flexural strength.

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Strength properties of monolithic ceramics have been studied from the viewpoints of fundamental strength and practical application through the interdisciplinary research and development of ceramic applied equipment such as a gas turbine, an automobile engine and so on by researchers, engineers and material researchers. However for the design, manufacture and reliability estimation for various commercial equipment using ceramics, the ceramics based on a fundamental strength evaluation does not necessarily result in sufficient safety and reliability of actual ceramic components, because of foreign object damage (FOD), Hertz crack generation and chipping failure due to ceramic brittleness. Therefore, by extracting the basic concept and data of ceramic strength for functional and structural design from research for practical applications as well as interdisciplinary research, the author would like to emphasize in this paper significant points concerning the ceramic strength estimation method useful for the application of practical engineering international standard.

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