This paper analyzes the available data on phase equilibria in the TiO₂–SiO₂–ZrO₂ system. The advantages of specialized databases and software systems for the analysis of information on phase equilibria are pointed. Phase diagrams are kind of a roadmap for the design of materials. As shown in the review, nanomaterials are no exception to this. Data on phase equilibria, such as eutectic points, solubility limits, binodal and spinodal curves, make it possible to predict the possibility of the formation of nanoscale structures and materials based on them. In its turn during the transition to the nanoscale state, the mutual component solubility, the temperature of phase transformation may change significantly, and other features may become observable. This provides additional variability when choosing compositions and material design based on the phases of a given system. As an example, for design of nuclear fuel assemblies that are tolerant to severe accidents at nuclear power plants, mixed carbides (so-called MAX-phases) are considered as one of the most promising options as nanoscale layers on fuel cladding. It is suggested that the materials of the TiO₂–SiO₂–ZrO₂ system, which are the product of oxidation of some MAX-phases, can serve as an inhibitor of their further corrosion. Ensuring the stability of materials based on MAX-phases expands their prospects in nuclear power. This requires comprehensive information about phase equilibria and formation conditions of nanostructured states in the analyzed system.