Loading rate effects on the fracture behaviour of solar control coatings during nanoindentation

Displacement control nanoindentation tests with a sharp cube corner indenter have been conducted on a range of thin oxide coatings (similar to 400 nm) deposited on soda-lime glass to generate radial through-thickness fracture within the impression. It was observed that the threshold fracture load for all coatings increased dramatically when the displacement rate increased from 20 nm/s to 40 nm/s. Both SnO2 and ITO coatings display different behaviour compared to the other oxide coatings tested in this study (TiOxNy, and ZnO) and other ceramic coatings reported in literature; once through-thickness fracture is well-established the maximum load reached in the test increases with loading rate whereas it remains constant for the other coatings. This has not been observed in similar test conditions where fracture was absent or when fracture is caused by a blunt Berkovich indenter and is related to phase changes in the tin oxide coatings. (C) 2007 Elsevier B.V. All rights reserved.