Ceramic Films and Coatings PDF

ABSTRACT

Stresses are important in both the processing and properties of ceramic films. The stresses in the film can be tensile or compressive and they have origins such as: epitaxy, growth processes, chemical reactions, thermal expansion mismatch and differential densification. This paper briefly reviews methods for measuring and calculating film stress, and the processes by which the stresses can cause mechanical failure of films. Specific examples that are discussed include: drying of granular alumina films, stresses induced by silicon nitride stripe films on silicon, tensile cracking of sol-gel films and compressive spalling of chromia films formed by oxidation of stainless steel.

The review highlights the importance of finite element methods for analysing stress distributions and the phenomenon of a critical film thickness that must be exceeded before mechanical failure occurs for a given level of film stress.

Edited by: W.E. Lee