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 a pplications. The results show that the grain-boundary conductivity of plasma-sprayed yttria-zirconia increases with decreasing precursor-par ticle size. Small particles are shown to melt more completely in the p lasma, and their improved flow on the deposit reduces intersplat poros ity and the barriers to oxygen-ion transport. The grain-interior condu ctivity also increases with decreasing precursor-particle size, owing to the diminishing presence of the monoclinic phase in the deposit. Yt tria is homogenized in the small particles during plasma spraying, whi ch suppresses the monoclinic transformation on cooling.