Nickel - yttria stabilized zirconia (Ni-YSZ) cermet was prepared by dispersing YSZ powder in a nonaqueous nickel nitrate solution followed by milling, drying and calcination. Concentration of nickel was varied between 10 and 60 volume percent (v/o). Samples were prepared by varying sintering temperature (1200-1350°C) and soaking time (2-6h). Hydrogen treatment was done in order to reduce nickel oxide to metallic nickel. Electrical conductivity of the samples was measured in the temperature range of ambient to 1000°C under hydrogen atmosphere. The temperature dependence of conductivity follows Arrhenius behavior. Plot of conductivity against temperature with nickel concentration gives rise to "S-shaped" curves. For each temperature a sudden rise in conductivity at around 30 v/o has been observed. The higher conductivity obtained at > 30 v/o nickel concentration is due to the percolation through interconnected Ni-chains in the YSZ matrix. A detailed microstructural investigation is also reported.
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