47,49Ti NMR:: Evolution of crystalline TiO2 from the gel state

Ti-47,Ti-49 NMR has been used to monitor the transition to the crystalline state of titania gels, formed by the hydrolysis of titanium isopropoxide, which were progressively annealed to 700 degrees C. The gel spectrum consists of a single unresolved line, considerably narrower than that for anatase. The spectra from the intermediate anneals indicate the additional presence of only crystalline TiO2 anatase and rutile (the final product) and that these polymorphs coexist over a range of temperatures of at least 100 degrees C in the specimen, indicating the spatially inhomogeneous development of crystallinity in these gel specimens.