NANOLAMINATED OXIDE CERAMIC COATINGS IN THE Y2O3-Al2O3 SYSTEM

Oxide ceramic coatings in the Y2O3-Al2O3 system were deposited by MOCVD using a screw feeding system. The pure Al2O3-coatings as well as the coatings containing Al2O3 and Y2O3 show a nanolaminated microstructure whereas pure Y2O3-coatings reveal a feathery microstructure. Further experiments with modified deposition parameters were carried out in order to control the lamellae characteristics. Therefore the stoichiometry of the starting material, the precursor feeding rate and the substrate temperature were varied systematically. Highly distinctive lamellae were found when the coating was deposited at a low substrate temperature or using an aluminum-rich starting material and a high precursor feeding rate, respectively. Annealing experiments in air and flowing water vapor of the nanolamellar structured baseline coating were carried out in order to investigate the microstructural development. Coalescence of nanopores to larger pores was observed while the lamellar coating morphology maintains.