Nanolaminated oxide ceramic coatings in the Al2O3-Y2O3 system

Kurzfassung

Oxide ceramic coatings are of particular interest for thermal and environmental protection of engineering materials. Coatings in the Al2O3-Y2O3 system ranging from pure Al2O3 to YAlO3 were deposited by MOCVD using a screw feeding system with flash evaporation. Investigations by means of scanning and transmission electron microscopy reveal a nanolamellar microstructure. The nanolamellae result from porosity and grain size fluctuations combined in some cases with an inhomogeneity of phase formation. The nanolamellar microstructure makes the coatings highly interesting for thermal barrier coating (TBC) applications because multiple phase boundaries or grain boundaries reduce phonon scattering as well as phonon transport which may contribute to a lowering of the thermal conductivity. Annealing experiments up to 1300°C were carried out in order to prove the high temperature stability of the promising microstructure.