Preprints of Annual Meeting of The Ceramic Society of Japan<br> Preprints of Fall Meeting of The Ceramic Society of Japan

Preparation of bulk of calcium carbonate was attempted by EPD method. Calcium carbonate bodies obtained by EPD were characterized by XRD and TG-DTA technique. Furthermore, calcium carbonate bodies obtained by EPD were treated under hydrothermal conditions. Their microstructures and components were observed by OM, SEM, TEM, and XRD.

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The recovery method of manganese from waste electrolytic solution was investigated. NaOH solution and NH₄Cl-NH₄OH buffer solution were used for controling pH in order to extract Mn from the waste. As a result, it was found that the use of NH₄Cl-NH₄OH buffer solution was effective for resource of manganese from waste electrolytic solution.

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The microwave reflection intensity (r) was measured for Al2O3 (ALO), SrTiO3 (STO) single crystal substrates and BaTiO3 (BTO) ceramics at room temperature using a single probe as a function of distance between sample and probe. The reflection coefficient (G) of samples was estimated in comparison with results of electromagnetic simulation using finite differential time domain (FDTD) method. The difference of r spectra for ALO, STO single crystal substrates and BTO ceramics at 9.43GHz was observed in the region where the distance of 0.2 mm (ALO, STO) and 0.35mm (BTO) between sample and probe, and they were caused from dielectric constants of samples. The r intensities of ALO and STO single crystal were transformed to dielectric permittivity at r intensity minimum points.

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Size effect on crystal structure has been investigated for barium titanate (BaTiO₃) nanoparticles of 40, 140 and 430 nm sizes, by means of neutron and high-resolution synchrotron X-ray powder diffraction and Raman scattering techniques. These samples are prepared by a modified 2-step thermal decomposition method from barium titanyl oxalate, resulting in very less lattice impurities. Rietveld analysis of neutron diffraction data of the 430 nm- and 140 nm-sized BaTiO₃ particles were performed assuming a single phase of tetragonal (P4mm) structure. The axial ratio c/a of tetragonal BaTiO₃ decreases with decrease of particle size from 430 nm to 140 nm, suggesting a soft-mode mechanism for high dielectric constant of BaTiO₃ particles with the size of 140 nm. Barium titanate particles with the size of 40 nm consist of (1) tetragonal crystals (83 wt%) with a large cell volume and axial ratio of near unity, and of (2) hexagonal phase ( P6₃mmc, 17 wt%) with a large unit-cell volume, leading to low dielectric constant. Rietveld and maximum-entropy method analyses strongly suggest that there exist atomic displacements from the ideal site of cubic structure and a spontaneous polarization of the tetragonal phase even in the 40 nm-sized BaTiO₃ particles. The nuclear density distribution of the 140 nm-sized particles with high dielectric constant does not exhibit very large positional disorder, while the Ba atom of tetragonal BaTiO₃ in the 40 nm-sized particles has a smaller atomic displacement parameter.

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