Phase composition and microstructure of vacuum plasma sprayed nanostructured zirconia coating

Nanostructured zirconia coating was deposited via vacuum plasma spraying (VPS). The phases and microstructure of the coating were characterized by XRD, Raman Spectroscopy, SEM and TEM. The surface chemical state was analyzed by X-ray photoelectron spectroscopy. It was found that the as-sprayed zirconia coating had two kinds of grain size distributions, one ranging from 500 to 1000 nm, and the other ranging from 40 to 110 nm. The as-sprayed zirconia coating was porous (20–25%) and it was composed of tetragonal phase zirconia. It appears that oxygen depletion occurred during VPS deposition. In the mostly crystalline zirconia grains, an amorphous region was also observed. Finally, some superlattice structures were observed in the as-sprayed zirconia coatings.