FORMATION AND SURFACE-STRUCTURE OF TI-ZN-DOUBLE OXIDES AND OF ZN FERRITE

In powder mixtures of ZnO and TiO2 the compounds Zn2TiO4, ZnTiO3, and Zn2Ti3O8 can be formed as a result of solid state reactions. The forma tion of the double oxides is essentially determined by the microstruct ure of the powder mixture. Furthermore, the type of the double oxide d epends on the TiO2 modification. There exist structural similarities b etween Zn2TiO4 (spinel) and TiO2 (anatase) as well as between ZnTiO3 a nd TiO2 (rutile). Compound Zn2Ti3O8 is formed only on the basis of the Zn2TiO4 phase. The Zn2+ ions on the surface of Zn2Ti3O8 occupy only t etrahedral sites and not octahedral ones, like it was derived for the crystal structure of the bulk. The formation of zinc ferrite, ZnFe2O4 at room temperature is possible by means of mechanical activation in a high-energy ball-milling process of a ZnO-Fe2O3 mixture (mechanosynth esis). The surface structure of mechanosynthesized zinc ferrite corres ponds to the inverse spinel structure type. The structure of inverse s pinel type is also created by means of mechanical activation of zinc f errite of the normal spinel type.