Influence of Zirconia Sol-gel Coatings on the Fracture Strength of Brittle Materials

In this work, the effect of a sol-gel ZrO₂–3 mol% Y₂O₃thin film on the fracture properties of a variety of brittle substrates was investigated. The results suggest that the film does not have any appreciable influence on the fracture behavior of crystalline substrates but dramatically affects the fracture properties of amorphous layers. In particular, a significant reduction of average fracture strength and a major increase of the Weibull modulus were observed on coated glassy slides. The origin of such variations is attributed to the generation of a homogeneous flaw population in the vitreous substrates, and the possible mechanisms for the production of flaws are analyzed. Implications of these results for the practical use of coated glassy layers are discussed.