"Nanohardness and Fracture Toughness of Combustion Chemical Vapor Depos" by D. W. Stollberg, W. B. Carter et al.
 

Nanohardness and Fracture Toughness of Combustion Chemical Vapor Deposition Deposited Yittria Stabilized Zirconia–Alumina Films

Document Type

Article

Publication Date

7-1-2005

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.

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