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Structure ofxPbO–(100− x)SiO2 (x=25–89) glasses has been investigated by means of the X-ray and neutron diffraction and29Si MAS NMR measurements. In the radial distribution functions of all the glasses, the Pb–O correlation was observed at 0.23 nm, indicating that the PbO3 trigonal pyramids units do exist in the whole glass forming composition range. Furthermore the existence of the first Pb–Pb correlation at∼0.385 nm in the whole composition range suggests that the basic structural unit is considered to be a Pb2O4 unit, which consists of the edge-shared PbO3 trigonal pyramids. These results strongly imply that the Pb2O4 units participate in the glass network constructed by SiO4 tetrahedra even at low PbO content. Differing from other lead-containing glass systems, these structural characteristics of Pb ions in the PbO–SiO2 glass system are responsible for the extremely wide glass-forming region. [ABSTRACT FROM AUTHOR]

Investigates the structure of PbO-B[sub 2]O[sub 3] glasses using X-ray diffraction and B MAS nuclear magnetic resonance techniques. Structural models of lead borate glass; Impact of PbO content on lead atom coordination; Formation of glass networks in higher-PbO glasses; Distribution of lead ions in the borate network; Limitation in the glass-forming region of binary glasses.

The traditional Japanese overglaze ceramic, akae porcelain, typically known for Kakiemon-style wares, has been prized around the world for over 400 years. The red color of akae porcelain provides an attractive contrast to white porcelain. In recent years, because the use of leaded frit in making akae has been restricted by law owing to the effects of lead on human health and the environment, lead-free glass frit mixtures for overglaze ceramic wares have been developed in various porcelain production areas throughout Japan. However, current lead-free frit for red overglaze enamels produces a color that is duller than that of conventional leaded frit. Therefore, the development of red pigments that are suitable for use with lead-free frit is strongly desired. In this study, we used a hydrothermal process to prepare nanosized iron oxide and oxyhydroxide powders, which showed good particle dispersion in molten lead-free frit. The precursor paste was prepared by reacting iron nitrate with ammonium hydrogen carbonate and heated in a sealed vessel at 80-150 °C. The sample powder prepared at 90 °C was almost monophasic α-Fe 2 O 3 (hematite) and exhibited the brightest red color (highest L *, a *, and b * values). This powder featured primary particles of ∼15 nm in diameter that aggregated to form secondary spherical particles of ∼100 nm in diameter. This powder was mixed with lead-free frit and applied as a red paint to a porcelain test piece. The resultant akae showed a bright red color with high L *, a *, and b * values that exceeded the values of akae prepared using conventional hematite powder. Microscopic analysis revealed that the hematite particles were well dispersed in the resultant glass layer, indicating that the hematite powders have good dispersibility in molten frit., Competing Interests: The authors declare no competing financial interest.