The capability of whole-powder-pattern decomposition in the quantitative phase analysis (QPA) of natural products was investigated using three- to six-component mixtures and pottery bodies. Here, the term pottery body means plastic clay suitable for making pottery and it is compounded of ceramic raw materials. Average errors of the weight fractions for each phase were within 1 weight percent in each mixture of natural products. The amounts of reduced oxides in pottery bodies derived from the X-ray diffraction technique were in good agreement with results obtained by X-ray fluorescence analysis. The present procedure does not require knowledge of crystal structures; it appears adequate for the QPA of natural products.

CaSiO3 powders were prepared from an ethanol solution dissolving Ca(NO3)2 · 4H2O and Si(OC2H5)4 by the coprecipitation method using various concentrations of NaOH as precipitants. Some Na component remained in the precipitates without washing and strongly affected the characteristics of the resultant powders, but the Na residue was removed by a washing treatment. The precipitate prepared by using 0.33 mol/l of NaOH and twice-washing contained the lowest amount of Na residue. It was calcined at 500 and 900 °C, respectively, to crystallize CaSiO3 phase and ground by a planetary potmill. The ground CaSiO3 powder was sintered to about 89% theoretical density by firing at 1400 °C. By soaking the CaSiO3 sintered bodies in simulated body fluid (SBF) solution for various times, an hydroxylapatite (HAp) layer formed as aggregates of ball-like particles on the surface of the CaSiO3 sintered bodies after soaking for a short period; thereby, the CaSiO3 ceramics is suggested to have very good biocompatibility.

Crystallization behavior of various compositions of MgAl2O4 –SiO2 glasses was investigated. Glasses with chemical compositions from MgAl2O4/SiO2 = 1/1 to 1/8, spanning the range of cordierite composition (1:2.5) were prepared by a rapid quenching method using an arc image furnace and twin roller. During thermal treatment, all the glasses first crystallized to form high-quartz solid solution (HQss), then transformed to high-cordierite at higher temperature. Transformation from high-cordierite to low-cordierite required prolonged firing times even at high temperature. The crystallization temperature of HQss and the transformation temperature from HQss to high-cordierite changed only slightly in the glasses with MgAl2O4/SiO2 ratios greater than cordierite composition, whereas large increases were found for glasses with MgAl2O4/SiO2 ratios lower than cordierite. The HQss phase appeared in the samples spanning a wide MgAl2O4/SiO2 range and showed superlattice reflections which doubled the fundamental lattice parameters. The cause for HQss formation prior to the appearance of cordierite in these glass samples is discussed from a structural viewpoint involving ordering-disordering of SiO4 and AlO4 tetrahedra deduced from 29Si and 27Al MAS-NMR spectra.

Metastable liquid-liquid immiscibility region in the Al2O3–SiO2 system was calculated by a regular solution model using three sets of liquidus data from the stable phase diagrams reported. These calculations indicated that the immiscibility region was richer in Al2O3 composition than those reported before. A miscibility gap calculated using the liquidus data reported by Klug et al. [F. J. Klug, S. Prochazka, and R. H. Doremus, J. Am. Ceram. Soc. 70, 750 (1987)] (model A) ranged from 2.6 to 71 mol % Al2O3 at around 1000 °C, which was the most compatible result with the idea that metastable pseudotetragonal mullite crystallized at around 1000 °C became Al2O3-rich composition due to the immiscibility phase separation before mullitization among three sets of liquidus data.

Porous α-alumina ceramics were prepared using the spray-pyrolyzed powder from aluminum nitrate solution and aluminum sulfate solution. Porosity and pore size distribution of the samples were examined with respect to the forming pressure and firing temperature. The porosity obtained changed from around 80% in the green compacts to 60–70% in the fired bodies fired at 1500 °C. The porosity of 30–40% remained even by firing at 1700 °C. Although there was no significant difference in the porosity of the fired bodies prepared from the sulfate and nitrate solutions, the fired bodies prepared from the nitrate solution showed apparently larger pore size than those from the sulfate solution. Fired bodies with an average pore radius from 0.2 to 0.8 μm can be prepared by this method. The four-point bending strength of the fired bodies, which had a porosity of 57% and an average pore radius of 0.23 μm, was 35 MPa.