ABSTRACT
Yttria partially stabilised zirconia (PYSZ) is commonly deposited by electron beam evaporation for use as a thermal barrier coating in aero-engines. This paper considers how the material dissociates on evaporation and whether the degree of dissociation depends upon the operating conditions and the state of the melt. It is found that the zirconia does dissociate on evaporation with the liberation of oxygen-based species, especially at 32 amu, the most significant part of the evaporation occurs in the early stages of the run, as thereafter tunnelling effects into the melt reduce the overall evaporation rate. It was also observed that the evaporation tends to proceed as a result of individual granules evaporating separately, and the effect of thermionic support was also investigated. In this work on zirconia based coatings there is no indication of substoichiometry in the coatings as a result of the dissociation of the material.
