High-growth rate YSZ thermal barrier coatings deposited by MOCVD demonstrate high thermal cycling lifetime

Yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBC) were prepared by metalorganic chemical vapor deposition (MOCVD) using Y(OButn)3, Zr(OButn)4 precursors and O2 carrier gas. A thermodynamic analysis guided experiments by optimizing elemental molar (n) stoichiometric ratios for the (Zr–Y–O–C–H system). This analysis showed single-phase YSZ was favored at 950 °C, 1 kPa, nO/(nY + nZr) > 30, nY/(nY + nZr) = 0.06–0.10 (fixed nC, nH). Experimental YSZ growth had multiple phases (fcc, monoclinic), had a relatively high growth rate (43 μm/h, 1005 °C), had an Arrhenius dependence (845–950 °C, Ea = 53.8 ± 7.9 kJ/mol), had columnar grains (SEM analysis), and had a coating through-thickness nY/(nY + nZr) = 0.04 (EPMA analysis). Doubling the inlet yttrium precursor mole fraction resulted in fcc YSZ growth with a coating through-thickness nY/(nY + nZr) = 0.07. Hot-insertion thermal cycling of YSZ coatings on FeCrAlY bond coats showed >1000 h lifetime, matching current standards for EB-PVD YSZ coatings.