The conductivity of yttria-stabilized zirconia samples which had been produced by plasma spraying was investigated. The results showed that the grain boundary conductivity of the plasma-sprayed material increased with decreasing precursor particle size. Small particles were found to melt more completely in the plasma, and their improved flow on the deposit then reduced inter-splat porosity and consequent barriers to O-ion transport. The grain conductivity also increased with decreasing precursor particle size, due to the decreasing presence of the monoclinic phase in the deposit. The yttria was homogenized in the small particles during plasma spraying, and this suppressed the monoclinic transformation upon cooling.

C.L.Curtis, D.T.Gawne, M.Priestnall: Journal of Materials Science, 1994, 29[12], 3102-6