Phase composition of nanostructured zirconia coatings deposited by air plasma spraying

Plasma sprayed nanostructured yttria stabilized zirconia coatings were deposited using nanostructured powder. The phase composition and microstructure characterization of the nanostructured as-sprayed zirconia coatings were studied by TEM, FESEM and XRD. The results showed the as-sprayed nanostructured zirconia coatings exhibited the typical lamellar structure, which was mainly composed of column grains with a diameter around 100 nm. The primary phase of as-sprayed nanostructured coatings was non-transformable tetragonal zirconia (T′ phase) having near the overall yttria content of nanostructured as-sprayed coatings. In addition, the typical superlattice-type reflections of the tetragonal phase were observed in the as-sprayed nanostructured coatings. No monoclinic phase was observed in the nanostructured as-sprayed coatings. There existed small segmentation cracks with lengths in the size range around 10 μm in the coatings.