Structure and nanomechanical behavior of sol-gel derived thin films

ZrO₂ coatings are used in applications where properties such as high hardness, corrosion resistance and high temperature resistance are required. Whereas a variety of techniques can be used to deposit these coatings, the sol-gel process offers distinct advantages such as simplicity, and the ability to form homogeneous films at low processing temperatures. In addition, in contrast to films produced by conventional ceramic processing, sol-gel derived ZrO₂ films are known to possess unique properties including nanoscale porosity and crystallite size. Single layer, crack-free films several hundred nanometers in thickness can be produced. Thicker films require the build-up of multiple layers which have been deposited and heat treated separately to avoid fracture caused by stresses induced by shrinkage of the gelled film during heat treatment. In light of their properties multi-layer sol-gel derived films show promise for use as mold coatings for the high volume production of precision optics. It is well recognized, however that the dependence of the physical properties of the films on the interdependent variables such as processing conditions and chemistry require further study. Currently, we are investigating the near surface mechanical response of multi-layer sol-gel derived ZrO₂ thin films by nanoindentation. In particular, we are interested in the evolution of film hardness, elastic modulus and microstructure with heat treatment temperature. This work is part of our Germany-USA Transregional Collaborative Research Center on the Replication of Complex Optics.

Funding provided by:

NSF and DFG

Collaborators:

A. Mehner and W. Datchary, Stiftung Institut für Werkstofftechnik Bremen, Germany

Relevant publication:

Mehner, A., Datchary, W., Bleil, N., Mayr, P., Klopfstein, M.J. and Lucca, D.A., "The Influence of Processing on Crack Formation, Microstructure, Density and Hardness of Sol-Gel Derived Zirconia Films", Journal of Sol-Gel Science and Technology, 36 (2005) 25-32.

Datchary, W., Mehner, A., Zoch, H.-W., Lucca, D.A., Klopfstein, M.J., Ghisleni, R., Grimme, D. and Brinksmeier, E., "High Precision Diamond Machining of Hybrid Sol-Gel Coatings", Journal of Sol-Gel Science and Technology, 35 (2005) 245-251.

Lucca, D.A., Klopfstein, M.J., Ghisleni, R., Gude, A., Mehner, A., Datchary, W., "Investigation of Sol-Gel Derived ZrO₂ Thin Films by Nanoindentation", Annals of the CIRP, 53, (2004) 475-478.