A study of nanocrystalline CeO2/PrOx optoionic thin films: temperature and oxygen vacancy dependence

The structure and optical constants of praseodymia doped ceria thin films are reported with and without oxygen annealing. These films were prepared using an inorganic sol-gel route and crystallized into the cubic fluorite structure well below 400°C, with cell constants altering as a function of dopant concentration and oxygen treatment/vacancy concentration. The films were also nanocrystalline, continuous and highly transparent in the region between 350–1500 nm. Optical transmission decreased with increased crystallite size due to scattering, below 600 nm. The refractive indices of the films at 800 nm in the dispersion free region were shown to vary in direct proportion to the lattice parameter/vacancy concentration and temperature treatment, and varied between 1.77 and 2.26. It is therefore proposed that they should be suitable materials for application as transparent ion intercalation films and optoionic smart windows.