This paper reviews several recent improvements in new transmission electron microscopy (TEM) to characterize microstructures in advanced ceramics. Ultra high resolution electron microscopy (UHREM) is a powerful technique to discriminate the species of atoms which are located closer within 0.1 nm, and therefore light elements such as nitrogen and oxygen can be directly observed in the structure image. Low electron dose HREM can be applied to characterize soft ceramics such as zeolite and biomaterials by using slow-scan CCD camera system. High spatial resolution analytical transmission electron microscopy (AEM) can be materialized by designing the pole-piece with small gap and large solid angle for X-ray detector. The chemical composition and chemical bonding state in the very narrow region less than 1 nm can be analyzed by using the present pole-piece with energy dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS) in a field-emission TEM (FE-TEM). Ultra high temperature in-situ observation is performed using special laser heating holder. Sintering behavior of zirconia ultra fine particles, and chemical reaction of zirconia and silica are directly observed by TEM in-situ heating experiment. In addition, in-situ straining observation is possible to observe crack propagation in alumina ceramics by using the crack induced tension (CIT) method which is driven by piezo actuator or micro-step motor. On the basis of the newly developed TEM methods demonstrated here, an concept of “Active-Nano Characterization and Technology” were proposed.

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Alumina microspheres have been prepared by spray pyrolysis of Al(NO₃)₃ aqueous solutions by adjusting the flow rate of air as a carrier gas and the concentration of Al(NO₃)₃. A mixture of hollow α-Al₂O₃ microspheres in the range of 200-700 nm in diameter and solid microparticles of smaller size were prepared by pyrolysis of 0.5mol·dm^-3 Al(NO₃)₃ at 1300°C and subsequent calcination at 1300°C for 1h in air. The use of Al(NO₃)₃ aqueous solutions at concentrations higher than 0.5 mol·dm^-3 resulted in the formation of sponge-like α-Al₂O₃ microspheres containing many closed pores.

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The effect of LiF addition on the sintering of β-spodumene (Li₂O⋅Al₂O₃⋅4SiO₂, LAS) powders prepared by a sol-gel process was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Upon sintering LAS precusor powders pellet samples without LiF addition, obtained the crystalline phase was merely β-spodumene. The intensity of the (102), (211), (222) and (303) refections of the β-spodumene phase decreases with increasing LiF additive content up to 4.0 mass% and some β-spodumene converts to β-eucryplite. The activation energies for grain growth were 26.0 and 23.0 kcal/mol for the calcined LAS precursor powders with 1.0 and 3.0 mass% LiF (sintered at various temperatures for 10 h), respectively. The slopes of the linear dependence of the grain size on the cubic root of time are 0.35 and 0.37 for the LAS precursor powders with 3.0 mass% LiF sintered at 1250 and 1350°C, respectively, showing a diffusion controlled growth.

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Mechanical properties of spray-dried granules have been characterized in compression by repeatedly applying and stopping stress, In order to shorten the experimental time and obtain optimal conditions for reliably evaluating the relaxation behavior, we discussed the influence of compression rate, compression number, relaxation time and initial height of the granule bed, respectively. It was found that the stress relaxation of granules increased with increasing compression rate. It was also demonstrated that the stress relaxation was almost independent of the initial height of the granule bed, Furthermore on the one time compression and stress relaxation test, the results were found to be in good agreement with those obtained from the multiple compression and stress relaxation test. These results show that the experimental time can be shortened from a few hours to about ten minutes.

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Electrochemical NO_x sensors for high temperature applications were prepared coupling pellets of yttriastabilized zirconia (YSZ), an oxygen ion conductor, with a thick film of a semiconducting oxide (WO₃) as an auxiliary phase. The obtained sensors were exposed to the same atmosphere without the use of reference air. Electromotive force (EMF), polarization curves and aperometric measurements were performed in air and at different concentrations of NO₂ in air, at selected temperatures. Stable EMF values and fast response times were obtained. The sensors showed non-linear polarization curves. The role played by the electrolyte/electrode interface was determined by electrochemical impedance spectroscopy (EIS) tests: exposure to NO₂ did not affect the bulk but only the electrolyte/electrode interface.

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Two kinds of zeolites with different crystal structures with the composition of BaO⋅Al₂O₃⋅2SiO₂⋅xH₂O prepared by an ion-exchange technique were used as a precursor of celsian. The difference between the zeolite structures resulted in the difference in modifications of celsian obtained through a heating treatment. Ba-exchanged zeolite A became an amorphous material at 300°C with dehydration, and then generates a small amount of monocelsian in the amorphous material at 500°C. When successively at 950°C for 1h, hexacelsian formed in addition to the previously produced monocelsian. A single phase of monocelsian was obtained finally by heating at 1500°C for 8h. The specimen heated at 1700°C, however, became a single phase of exacelsian, owing to monocelsian-to-hexacelsian phase transformation. The structure of Ba-exchanged Linde F zeolite collapsed at 300°C with dehydration, and only hexacelsian formed at temperatures above 980°C. The reason for the formation of monocelsian only from Ba-exchanged zeolite A was explained in terms of the similarity in framework structures of zeolite A and monocelsian.

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The dense (Ti_1-xHf_x)C ceramics with a relative density of 95-98% for x=0.2 to 0.8 were made from powder mixture of TiC and HfC at 2000°C and 32 MPa in Ar by hot-pressing. The microhardness was determined to be 2760±90kg·mm^-2 (HV) for x=0.5. The formation of the mixed carbide (Ti_1-xHf_x)C was confirmed by X-ray diffraction.
Oxidation of (Ti_0.5Hf_0.5)C ceramics was performed at 1300 to 1500°C at 0.08kPa. It was assumed in the early stage that oxygen dissolves in (Ti_0.5Hf_0.5)C to form oxycarbide (Ti_0.5Hf_0.5)C_1-xO_x, followed by its decomposition to HfO₂ and TiO_x, with the microstructure of the respective gray and white stripes (subscale I). Subscale II is inherited from subscale I. At>3h, HfO₂ particles of 500nm in size were formed in a matrix of TiO_x containing amorphous carbon in subscale II. This scale thickens parabolically with time, which assumes that the diffusion of oxygen determines the oxidation. Faster outward diffusion of Ti from subscale II produces HfO₂ scale (subscale III) as the balance. TiO₂ formed already in the early stage (subscale V) is reacted with HfO₂, resulting in the formation of HfTiO₄ scale (subscale IV).

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A new synthetic route based on a solution chemistry was developed for a compound semiconductor indium antimonide (InSb). Considering the moisture sensitive properties of metal alkoxides, indium antimonide was synthesized by reduction of InSbO₄, which was prepared by hydrolysis of the corresponding metal alkoxides as starting materials. InSb-alkoxide solution was prepared by two ways: one is mixed method in which In-alkoxide solution and Sb-alkoxide solution were mixed simply, and the other is continuous method using the reaction of indium chloride with Na-alkoxide in the presence of Sb-alkoxide in ethanol. Hydrolysis products by both methods were crystallized to InSbO₄ by heat-treatment at 780°C in air. InSb was obtained by heat-treatment of hydrolysis product prepared by the continuous method at 400°C in H₂, but it wasn't obtained from hydrolysis product prepared by the mixed method. The primary particle size of hydrolysis products was about 8nm in diameters. The wet hydrolysis product was well mixed with ethylcellulose and terpineol by a three-roll mill to form printing paste. The paste was screen-printed on slide glass substrates, transformed to InSb film by heat treatment at 400°C in H₂.

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Superconductors, Tl_2-zBa₂Ca_1.95Y_0.05Cu₃O_y, with variable Tl contents were prepared. We investigated the dependence of their properties, crystal structures and T_c on the Tl content. The Cu valence decreased with decreasing Tl content, 2-z, in the region of 2-z≥1.5 but increased in the region of 1.2≤2-z<1.5. The critical temperature, T_c changed with decreasing Tl content. T_c(zero) was 116 K at 2-z=1.7. When the Tl content was decreased, T_c(zero) reached the maximum value of 119 K at 2-z=1.2. The results of structure refinements of samples with different Tl contents with neutron powder diffraction data show that Cul-Ca, Y and Cu2-Ca, Y lengths had the largest and smallest values at 2-z=1.5. At this Tl content, T_c(zero) was the lowest of 108 K, and copper-apical oxygen (Cu2-O3) bond length was the smallest.

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The relationship between hyrophobicity and snow adhesion or snow sliding on various hydrophobic silica films was investigated. A super-hydrophobic film showed an excellent anti-snow adhesion property against both dry and wet snow, and a sliding acceleration of dry snow. However wet snow showed poor sliding behavior on the film, hydrophilic smooth glass surface being thus effective only for sliding of wet snow. It is deduced from experiments, utilizing water-hollow glass beads composite, that sliding behaviors of the composite on a super-hydrophobic surface depended on the solid concentration and was limited by line tension (solid<40%), viscous flow (40%<solid), and solid-solid friction (solid-100%). Based on the practical exposure results, it can be regarded that dry snow and wet snow are in solid-solid friction limited region and viscous flow limited region, respectively. The sliding of wet snow for hydrophilic surface might be limited by water film formation, and that for hydrophobic surface might be limited by viscous flow.

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Magnetic and electric properties of LaCo_xMn_1-xO₃ (x=0.0, 0.1, 0.3, 0.5, 0.7, 0.9, 1.0) compounds were measured by applying the Superconducting Quantum Interference Device (SQUID) in the magnetic fields of 0 and 5 tesla at low temperatures. Respective atomic valences and the fraction of Co and Mn ions were also examined by an X-ray Photoelectron Spectroscopy (XPS) method at room temperature. Discrepancies in the electric resistivity (Magnetoresistance) of the compounds under the conditions with and without an applied magnetic field decreased with an increase of Co ion, and the maximum point of each agnetoresistance vs. temp. curve corresponded with the Curie temperature of transition from paramagnetic to ferromagnetic. Judging from the values of the effective magnetic moment obtained from Curie constant and as a result of deconvolution of the XPS spectrum, it was found that Co and Mn ions in the compounds coexisted respectively at the mixed valence states. The electron configuration of the former ion was low spin states of Co^II+(t_2g⁶e_g¹) and Co^III+(t_2g⁶e_g⁰), whereas, that of the latter ion was high spin states of Mn³⁺t(t_2g³e_g¹) and Mn⁴⁺(t_2g³e_g⁰). It is probable that, in the present system compounds, the ferromagnetic double exchange interaction between Mn³⁺ and Mn⁴⁺ ions dominates over that between Co^II+ and Co^III+ ions.

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Lithium rare-earth silicate glasses, (Li₂O)_35.7(RE₂O₃)_7.2(SiO₂)_57.1 (RE=Sm, Gd, Dy, Ho, Y, Er and Yb), were prepared by melting a mixture of Li₂CO₃, RE₂O₃ and SiO₂ under the composition ratio of each component. The density was increased with increasing the atomic weight of RE. Three differential thermal analysis (DTA) exothermic peaks (T_c(I), T_c(II) and T_c(III)), attributed to crystallization, were observed in the temperature range of 650 to 880°C. The powder X-ray diffraction analysis indicated that Li₂SiO₃, (Li₂SO₃+RE₂Si₂O₇+RE₂SiO₅) and (Li₂SO₃+RE₂Si₂O₇) formed around T_c(I), T_c(II) and T_c(III), respectively. The conductivity of (Li₂O)_35.7(RE₂O₃)_7.2(SiO₂)_57.1 glass was found to increase about two orders of magnitude over that of the corresponding Li₅YSi₄O₁₂ ceramic.

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MgO thin films as a protective layer in plasma display panels (PDPs) were deposited by an advanced ion-plating (IP) method. Scanning electron microscopy and atomic force microscopy observations revealed that the IP films had columnar structures with sharp apexes at the film surface. The MgO thin films were mainly (111) oriented, and the orientation of the films was strongly dependent on oxygen content in the deposition process. The growth of (111) orientated films was promoted in IP method compared to conventional electron beam deposition (EB) method. The performance of MgO protective film could be expected to improve by the advanced ion-plating (IP) method for PDPs application.

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Conventional alumina and magnesia powders were mixed with a mica-composition glass powder, compacted, and fired. A dense spinel/mica composite was obtained at a low temperature of 1200°C for the specimen of 20% mica-composition glass addition. The sintering was promoted by not only the dissolution of fluorine ion but also the formed liquid phase. The liquid phase allowed the volume expansion caused by the reaction between the alumina and the magnesia to be effective for ensication, like a closer packing of particles. Furthermore, the liquid phase caused particle rearrangement and dissolution-precipitation. Numerous flakelike mica crystals of several micrometers separated out in the interparticle regions of the spinel. Both brittle and quasi-plastic damage modes were competitive on the surface and in the subsurface of the specimen. The bending strength was slightly decreased by Hertzian indentation. The fracture site in the post-indented specimen was a cornlike crack. However, the quasi-plasticity prevented catastrophic failure from the cor-nlike crack. These results indicate that the composite had flaw tolerance.

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Zn₂SiO₄: Mn²⁺ thin films were fabricated by spray pyrolysis. FT-IR spectroscopy was applied to study both the chemical reactions in solution during the preparation of spray solutions and pyrolysis of the deposited films. Spray solutions were prepared by two routes: (1) a reaction based on the formation of ZnO nanoclusters from zinc acetate (ZnO cluster route), (2) a reaction based on the hydrolysis of tetraethylsilicate (silicate hydrolysis route). The progress of the reactions in ethanol solution was discussed from the wavenumber difference between two absorption peaks of the carboxylic group of acetic acid from zinc acetate. The pyrolysis process was monitored in-situ by high-temperature IR transmission spectra, which clarified the thermal degradation process of organic contents and the state of amorphous inorganic residues.

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