Atomic-scale structure of ZrO₂ xerogels by X-ray diffraction and reverse Monte Carlo simulations

Structure functions for two amorphous ZrO₂ xerogels have been determined by X-ray diffraction experiments. Three-dimensional structure models consistent with the experimental data have been constructed by reverse Monte Carlo simulations. Partial distribution functions, interatomic distances and coordination numbers have been extracted from the model atomic configurations. Local atomic ordering in the as dried ZrO₂ xerogel resembles crystalline monoclinic ZrO₂ and the xerogel annealed at elevated temperatures resembles that in crystalline tetragonal ZrO₂. A comparison between structure data for zirconia xerogels obtained under different preparation conditions was made and evidence was found that thermal treatment at elevated temperatures and preparation conditions affect the atomic arrangement of amorphous ZrO₂. A structural mechanism explaining why zirconia gels with different local atomic arrangements may be obtained under different preparation and thermal conditions is advanced.