PROCESSING AND CHARACTERIZATION OF POROUS TIO2 COATINGS

Titania coatings were prepared by spin coating anhydrous titanium ethoxide solutions onto Si substrates. During deposition, Ti ethoxide in the solution layer reacted with atmospheric moisture to form precipitated particles. The resulting microstructures were composed of a network of particles and particle clusters. The induction time for precipitation, the particle diameter, and the size and packing of particle clusters were influenced by the Ti concentration in the sol and the spinning rate used for deposition. Individual particle sizes ranged from approximately 150 to 250 nm. Smaller particles and more compact particle clusters were characteristic of coatings prepared from solutions with lower Ti concentrations and those prepared using faster spinning rates. As-deposited coatings were amorphous and crystallized into the anatase phase at approximately 400-degrees-C. Transformation to the rutile phase began at approximately 850-degrees-C, and the transformation rate was influenced by the microstructure.