The role of processes on the surface in organization of long range mass-transport in the bulk

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 degreesC at atmospheric pressure in air. The characterization of YSZ coating structure was carried out 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 interface. The conducted analysis showed 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 thermodynamic potentials supports an intensive intermixing across Y/Zr layers with continuous supply of oxygen through the surface. Under highly non-equilibrium conditions on the surface, the adatoms are driven into grain boundaries of crystallites and result in high compressive stress in grains. The stress relaxation initiates the plastic flow of matrix material with incorporation of oxygen atoms. Thermally activated dislocation glide is considered as the dominant plastic-deformation mechanism in these materials.