Modeling of the reaction interdiffusion in the polycrystalline systems with limited component solubility

Abstract

that may be accompanied by the processes of mutual diffusion and phase formation. Controlled technological process of forming coatings with the given properties entails the necessity of forecasting the evolution of the phase composition. This in turn requires the development of algorithms and quantitative models of the processes. Reactive mutual diffusion in polycrystalline metal (oxide film systems with limited component solubility) has not been simulated before. The simulation allows selecting the annealing conditions (time and temperature) necessary for the inclusion and uniform distribution of metal in the oxide lattice. A quantitative model of the interaction in a multi-layer system metal — polycrystalline oxide of the other metal under conditions of limited solubility is developed. The model is based on the concepts of mutual diffusion of the components and the bulk reactions of the formation of complex oxides. The developed model was applied to the analysis of the process of modifying thin films of titanium oxide with transition metals. The model allowed us to perform a numerical analysis of the experimental concentrations of the component distributions in polycrystalline Co - Ti02 and Fe - Ti02 thin-film systems. The individual diffusion coefficients of the studied metals and titanium under conditions of vacuum annealing were determined. The model provides a good description of the basic systematic features of the process: the appearance of titanium in the metal film and deep penetration of Fe and Co into the film of titanium oxide. It also explains the fact that complex oxides are formed not by layer-by-layer growth at the metal-oxide interface, but throughout the entire thickness of Ti02 film. The results of analysis of the processes of interracial interaction in layered systems accompanied by the reaction mutual diffusion can be used to predict the evolution of the phase composition, as well as to control the technological processes of obtaining materials with the desired properties.