Structure and optical properties of nanocrystalline yttria doped ceria thin films

Thin films of Ce1-xYxO2-y where x ranges from 0 to 0.5 have been coated onto glass substrates using an inorganic sol-gel approach at low temperature. The lattice parameters from powder diffraction measurements were calculated and shown to be very close to those previously reported. Crystallite size measurements indicated that the films were nanocrystalline, the size decreasing as a function of dopant concentration. The films are transparent in the region 500 to 1500 nm with very low optical losses. The film refractive index is dependent on the dopant concentration and peaks at an yttria concentration of x = 0.25 after treatment at 450 degrees C, with a value of 1.79, which on increasing the yttria concentration to x = 0.50 decreases to 1.65 in the dispersion free region. The optical band gap is also dependent on the dopant concentration and is in the range 3.2 to 3.0 eV.