Abstract
α-Fe_2O_3 (hematite) is famous as a red color pigment and called bengala in Japan. Our materials science studies on beautiful red color of two different kinds of Japanese traditional iron oxide ceramics in Okayama area are explained. Beautiful red color of Fukiya bengala developed as red pigments in the 18^<th> century has been made unclear for long time. We found that the Al substitution was very important in the bengala. Characteristic reddish color pattern, "Hidasuki", on Bizen stoneware, unglazed ceramics, is made from reactions between clay and rice straw. We have experimentally understood the microstructure and formation process of the red color pattern due to dispersion of Fe_2O_3 particles precipitated on Al_2O_3 particle in thin surface glass layer during extremely slow cooling process. "Iron-oxidizing bacteria" produce extracellular, uniquely-shaped microsheaths comprising mainly iron oxides - known as Biogenous iron oxides (BIOX) - ubiquitously in natural hydrosphere at ambient temperature. Although BIOX has been generally recognized as waste, we have studied not only nano-structure, chemical composition and crystal structure but also its properties for as yet unknown potential industrial applications.
