Silica-titania planar waveguides doped with Er 31 ions, obtained by the sol-gel process, have potential application in integrated optics amplifiers for 1.54 mum. Controlled precipitation of Er-containing nanocrystals may be achieved to maximize the quantum efficiency of the rare earth ion. Silica-titania thin films, prepared by sol-gel processing, were doped with less than or equal to 2 at % of erbium and, in some cases, with phosphorous; they were then heat-treated between 900 degreesC and 1100 degreesC, in order to promote the precipitation of erbium-containing nanocrystals: erbium dititanate (Er2Ti2O7) and erbium metaphosphate (ErPO4). The heat-treated films, as well as the erbium containing crystal phases were characterized by X-Ray Diffraction, Raman and Extended X-ray Absorption Fine Structure spectroscopies, Atomic Force Microscopy and Transmission Electron Microscopy.