The deposition of nanostructured yttria stabilized zirconia coatings via the solution precursor plasma spray process

Zirconia stabilized with 7-8 wt.% yttria is a ceramic material widely used for thermal barrier coatings and as an electrolyte for solid oxide fuel cells. Nanostructured yttria-stabilized zirconia coatings offer the potential improved properties over polycrystalline coatings for the same applications. Attempts to synthesize such coatings by thermal spraying using ceramic precursors in solution form have recently been described. This research involves the implementation and optimization of a solution precursor plasma spray (SPPS) process, for the deposition of nanostructured zirconia coatings with an 8 wt.% yttria content. A series of designed experiments was conducted to systematically investigate the influence of process variables on the coating characteristics. The process parameters investigated were substrate temperature, primary plasma gas flow-rate, plasma torch current, precursor mass flow-rate, and substrate stand-off distance. The coating characteristics included porosity, hardness, phase composition, and elemental distribution.