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Abstract: Composite films with compositions of 100% yttria stabilized zirconia (YSZ) and YSZ with 15, 30, 45, 62.8 (eutectic composition), 80 mol% alumina and 100% alumina films were deposited onto sapphire substrates using combustion chemical vapor deposition. Precursors of yttrium 2-ethylhexanoate, zirconium 2-ethylhexanoate and Al acetylacetonate dissolved in toluene at a total metal ion concentration of 0.002 M were used to produce films up to 1 μm thick. Flame temperatures at the substrate surfaces were 1550±50 °C and deposition rates fell between of 0.76–1.7 μm/h, depending on composition. Nanohardness, determined with a Berkovich indenter, was constant at about 15 GPa for compositions less than 100% alumina. The 100% alumina films were about twice as hard as other films. The films'' fracture toughness, determined with a cube corner indenter, increased with alumina content from 1.76±0.46 MPa m0.5 with no alumina to 2.49±0.32 MPa m0.5 at 30 mol% alumina. Further alumina increases had little effect on fracture toughness, with about 2.2 MPa m0.5 being the fracture toughness at 100% alumina. Eutectic composition films, that were annealed for 2.5–10 h at 1500 °C, displayed coarsening of the second phase YSZ particles. Film hardness decreased by about half (∼22 to ∼11 GPa) after five or more hours of annealing, while fracture toughness reached a maximum of 3.33 MPa m0.5 after a 5 h anneal. [Copyright &y& Elsevier]

Combustion chemical vapor deposition (combustion CVD) was used to deposit thin films of yttria stabilized zirconia (YSZ) and alumina (Al2O3). Nanoindentation analysis for hardness, modulus and fracture toughness of the films as well as several bulk materials, including single crystal Al2O3, MgO, SiO2, YSZ and polycrystalline Al2O3 was conducted. YSZ films that were produced with a total cation molarity of 0.005 M possessed significant surface roughness that was not conducive to nanoindentation measurements. The lower concentration investigated, 0.002 M provided a repeatable deposition condition that produced thin films with consistent hardness and modulus values. Load-displacement measurements at very low loads (up to total displacements of 200 nm) showed that the Al2O3 films tended to plastically deform, whereas the YSZ films showed less of a tendency to do so. For Al2O3 films that were 0.38±0.09 μm thick, the modulus, hardness and fracture toughness values were 28.6±1.6 GPa, 479±15 GPa and 2.22±0.31 MPa m0.5, respectively; for YSZ films that were 0.65±0.05 μm thick, the values were 16.1±4.6 GPa, 388±89 GPa and 1.67±0.46 MPa m0.5, respectively. These values were found to be consistent with the values measured via nanoindentation in this work for bulk samples of Al2O3 and YSZ, as well as to those reported in the literature. [Copyright &y& Elsevier]