THE PROCESSING AND ELECTRICAL-PROPERTIES OF PLASMA-SPRAYED YTTRIA-ZIRCONIA

The electrical conductivity of yttria-stabilized zirconia produced by plasma spraying was investigated with special reference to fuel-cell applications. The results show that the grain-boundary conductivity of plasma-sprayed yttria-zirconia increases with decreasing precursor-particle size. Small particles are shown to melt more completely in the plasma, and their improved flow on the deposit reduces intersplat porosity and the barriers to oxygen-ion transport. The grain-interior conductivity also increases with decreasing precursor-particle size, owing to the diminishing presence of the monoclinic phase in the deposit. Yttria is homogenized in the small particles during plasma spraying, which suppresses the monoclinic transformation on cooling.