Abstract: Conventional and nanostructured Al₂O₃-3wt%TiO₂ coatings were deposited by plasma spraying with conventional and nanostructured powders, respectively. The phase compositions and microstructure of the as-spraying coatings were characterized by XRD,
SEM and TEM. The electrical resistivity, dielectric constant and dielectric loss of coatings were measured. In both conventional and nanostructured
Al₂O₃-3wt%TiO₂ coatings, alumina mainly existed in the form of γ-Al₂O₃ with some α-Al₂O₃. Non-stoichiometric Ti₂O₃ was found in the conventional coating; while in the
nanostructured coating, titania reacted with alumina to form solid solution. The conventional Al₂O₃-3wt%TiO₂ coating exhibited a typical splat
microstructure. For the nanostructured Al₂O₃-3wt%TiO₂ coating, many equiaxed α-Al₂O₃ grains besides splat lamellae were also observed.
The size of equiaxed α-Al₂O₃ grains was about 150～800nm. Compared to the conventional Al₂O₃-3wt%TiO₂ coating, electrical
resistivity of the nanostructured Al₂O₃-3wt%TiO₂ coating increased. But the nanostructured coating exhibited lower dielectric constant and
dielectric loss.

Key words: plasma spraying, Al₂O₃-TiO₂ coating, nanostructure, electrical properties