Columnar and feather-like structure formation of yttria-stabilized zirconia layers prepared by electron beam physical vapor deposition

Yttria-stabilized zirconia (YSZ) layers were prepared by electron beam physical vapor deposition (EB-PVD) in order to investigate the formation mechanism of columnar and feather-like structure. Substrate rotation caused a drastic change in morphology and porosity of the YSZ layers. The layer deposited on a stationary substrate comprised relatively dense-packed columnar grains. The layers deposited on rotated substrates consisted of columnar grains separated by submicron gaps. These columnar grains contained well-developed feather-like structures with nano-scale gaps and pores. The flux shadowing effect, which was understood as an interruption of vapor flux incident obliquely to crystal growth orientation during substrate rotation, was the origin of the columnar and feather-like structure formation by EB-PVD. Mechanism of porous structure in the EB-PVD layers can be classified into three types, in relation to competitive growth of columnar grains, substrate rotation and rotation speed.