Microstructure of nanoporous yttria-stabilized zirconia films fabricated by EB-PVD

Microstructures of ZrO2–4 mol% Y2O3 coating layers fabricated by EB-PVD are characterized. Coating layers are found to consist of porous columnar grains with a feather-like structure containing evenly dispersed nano-sized gaps. Nanopores less than 50 nm in diameter could also be observed within columnar grains. The columnar grain size and column width of the coating layers increased with increasing coating thickness and substrate rotation speed. The porosity of the coating layers also shows increases with increasing substrate rotation speed. Specimens rotated at 1 rpm are found to contain wavy or scalloped columnar grains. Specimens rotated at higher speeds are found to consist of straight columns with a banded structure.