Coatings of yttria-stabilized zirconia formed by annealing of Y/Zr layers in air

Abstract

Yttria-stabilized zirconia (YSZ) coatings were synthesized using dc magnetron sputter deposition of Y/Zr layers followed by thermal treatment in the range of temperatures 600-1000 degrees C under atmospheric pressure in air. The YSZ coating structure was characterized by X-ray diffraction. The secondary ion mass-spectrometry analysis was used for the recording of depth profiles of the most important elements in coatings and at the interface. Surface roughness and topography was monitored employing atomic force and scanning electron microscopies. The analysis shows that processes on the surface play a dominant role in the synthesis mechanism of YSZ coatings, homogeneous in structure and composition, during the thermal oxidation. The excess of surface chemical potential and surface energy induce intensive intermixing between Y/Zr layers with continuous supply of oxygen through the surface. Under highly nonequilibrium conditions on the surface, the oxygen atoms are driven into grain boundaries of crystallites, and this results in high compressive stress in grains. The stress relaxation initiates the plastic flow of the matrix material with incorporation of oxygen atoms.[...]