Nanoindentation of YSZ-alumina ceramic thin films grown by combustion chemical vapor deposition

Yttria-stabilized zirconia (YSZ), alumina (Al2O 3), and YSZ-Al2O3 composites were deposited onto single crystal a-plane alumina using combustion chemical vapor deposition (CVD). Using an organic liquid as the flammable solvent and Y 2-ethylhexanoate, Zr 2-ethylhexanoate and Al acetylacetonate as the metal precursors in a 0.002 M concentration, films were grown with deposition rates of ∼1.5 mum/hr. The mechanical properties (hardness, elastic modulus and fracture toughness) of the films were measured using nanoindentation. Additions of second phase particles of Al2O3 to YSZ films increased the fracture toughness. Similarly, additions of second phase particles of YSZ to Al 2O3 films also increased the fracture toughness. Modeling of the fracture toughness of the YSZ-Al2O3 films was successfully achieved using the following toughening mechanisms: crack deflection from the second phase particles, grain bridging around the particles and residual stress from the CTE mismatch between the film and the substrate and between the second phase particles and the matrix of the film.