Controlling grain size in columnar YSZ coating formation by droplet filtering assisted PS-PVD processing
Grain size is important to the effect of material performance, particularly when reduced to nanoscale size. Generally, ionic conductivity in solid electrolytes can be remarkably enhanced by the nanostructure ceramics. In this study, a shrouded plasma torch was used on plasma spray-physical vapor deposition (PS-PVD) process. Multi-stage shielding was used to realize the controlling of grain size during the deposition process. The deposition behavior of YSZ was studied. The surface and cross-sectional morphology of the coating layer were also investigated. An island structure consisting of nano particle was seen on the coating layer surface, and the particle size becomes smaller with increased shielding stage. The cross section morphology of fracture coatings showed columnar structure. In this work, the grain size of the YSZ coating layer can be successfully controlled minimum to 25 nm by PS-PVD process. The effect of YSZ grain size on the coating properties is also discussed.