Preparation of Photocatalyst in Iron Oxide-Titania Solid Solution and Silica System through Two-Liquid Phase Separation

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In this study, the composite materials comprising continuous iron oxide-titania solid solution (Fe_<2-x>Ti_xO_3) phase were prepared by melting and quenching of the fired body in Fe_2O_3-TiO_2-SiO_2 system in order to fabricate a visible-light active photocatalyst.The fired bodies in the FeO-Fe_2O_3-TiO_2 ternary system were synthesized by use of the solid reaction process, and their crystalline phases, electric conductivities and photo-electrochemical properties were examined in order to search the optimum composition of iron oxide-titania solid solution as photocatalyst. The crystalline phase changed from spinel-type solid solution to α-phase type, and further to pseudo-brookite type with the decrease of the firing temperature and the increase of the amount of Ti component. The sample which contained both spinel-type and α-phase type solid solution showed high photocurrent density. Their density once increased with the ratio of α-phase type, and steeply decreased over about 60 % of t … More he ratio. The decrement of the sinter ability of the sample caused the increase of the grain boundaries and voids. As a result, the photo-excited electrons and holes easily were apt to recombine.On the base of above results, the preparation of the photocatalyst comprising iron oxide-titania solid solution was tried by quenching the melt in Fe_2O_3-TiO_2-SiO_2 ternary system. The obtained glass ceramics had the phase separation texture comprising SiO_2 rich and Fe_2O_3-TiO_2 rich phases The relation between crystalline phase and electric conductivity of the obtained glass ceramics was examined. The crystalline phase changed from α-phase type to α-phase + pseudo-brookite types, further to α-phase + spinel type solid solution with the increase of the amount of Fe component at the constant value of SiO_2, and the electric conductivity increased in the same order. These results were good agreement with those of the fired body in above FeO-Fe_2O_3-TiO_2 ternary system. However, it was hard to control the crystalline phase in the obtained glass ceramics because of their inhomogeneity of the compositions, and to leach the only SiO_2 rich phase from them, selectively.The next plan of the study is to investigate the relationship between crystalline phase and photo-current density in the homogeneous sample, more fully, and to achieve the visible light active photocatalyst by selecting the optimum conditions of the preparation process. Less