Colored films produced by electron beam deposition from nanometric TiO 2 and Al 2O 3 pigment powders obtained by modified polymeric precursor method

Abstract

Synthesis and the characterization of TiO 2:5%Co (green), TiO 3:5%Fe (brown-reddish), TiO 2:2%Cr (brown), Al 2O 3:5%Co (blue), Al 2O 3:5%Fe (brown-reddish) and Al 2O 3:2%Cr (light green) nanometric pigment powders using polymeric precursor (modified Pechini's method) is reported. Colored thick films were deposited on amorphous quartz substrates by electron beam physical vapor deposition (EB-PVD) using pellets of the pigment powders as target. The evaporation process was carried out in vacuum of 4 × 10 −6 Torr and the amorphous quartz substrates were kept at 350 °C during deposition. The TiO 2-based pigment powders presented crystalline anatase phase and the Al 2O 3-based pigment powders showed corundum phase, investigated by X-ray diffraction (XRD). The average particle size of the pigment powders was about 20 nm, measured by scanning electron microscopy with field emission gun (SEM-FEG). Diffuse reflectance spectra and colorimetric coordinates L ∗, a ∗, b ∗ using the CIE -L ∗ a ∗ b ∗ method are shown for the pigment powders, in the 350–750 nm range. The colored thick films were characterized by transmittance (UV–Vis) and atomic force microscopy (AFM). The average film roughness was ∼5.5 nm and the average grain size obtained in the films was around 75 nm. Films with thickness from 400 nm to 690 nm were obtained, measured by talystep profiler. Transmission spectra envelop method has been used to obtain refractive index and thickness of the Al 2O 3 colored thick films.