Optical constants of nanocrystalline lanthanide-doped ceria thin films with the fluorite structure

The optical constants and structure of yttria-doped ceria and ceria doped with Nd, Sm, Gd, Dy, Er and Yb oxides are reported. These films were prepared using an inorganic sol-gel route and characterized for their refractive index, optical absorption edge, structure and crystallite size. All the films crystallized into the fluorite structure well below 450 degrees C, with cell constants altering as a function of ionic radius. The films were also nanocrystalline and continuous, with crystallite sizes in the range of 10-16 nm after 600 degrees C. They have high transparency in the region 350 to 1500 nm and a reasonably high refractive index (1.7-1.79 at a wavelength of 800 nm) in the dispersion-free region. The dispersion behaviour in the refractive index has been fitted to the single oscillator model and is also shown to be dependent on the ionic size of the dopant material. It is therefore proposed that they should be suitable materials for application as transparent ion intercalation films and optoionic smart windows. (C) 1998 Elsevier Science Ltd. All rights reserved.