Novel sea-urchin-like rutile microstructures synthesized by the thermal decomposition and oxidation of K₂TiF₆

Sea-urchin-like rutile (su-TiO₂) microstructures were successfully synthesized by thermal decomposition and oxidation of a solid precursor, K₂TiF₆. During the synthesis, precursor temperature (640 C), N₂-flow (15 cm³/min) and inner pressure (90 mbar above the atmospheric pressure) remained constant. In order to evaluate the effect of time on the morphology of su-TiO₂, five levels (0.5, 1, 1.5, 2, and 2.5 h) were considered. The thermal decomposition an oxidation of the K₂TiF₆ precursor was studied by thermal analyses. It was found that TiO₂ was segregated from the matrix, leading to the formation of su-TiO₂ during processing. At 640 C, the precursor underwent thermal decomposition and oxidation that produced three different products: K₃TiOF_5(s), TiO_2(s), and F_2(g). The su-TiO₂ is synthesized only at t=2 h and t=2.5 h, presenting defined spikes at the former (100 μm×100 nm) and rougher structures at the latter (50 μm×10 μm).