Electrical conductivity in two phase nickel–nickel oxide mixtures and conductivity of nickel oxide at the nickel–nickel oxide phase boundary

The electrical conductivity of sintered pellets of nickel–nickel oxide mixtures of various compositions has been measured as a function of temperature in the range 700–1000 °C. The electrical conductivity of nickel oxide single crystals in air as well as in oxygen pressures corresponding to nickel–nickel oxide equilibrium has also been determined as a function of temperature. The conductivity of nickel–nickel oxide composites decreases initially, attains a minimum at approximately 1 mol % nickel and increases again with the increase in concentration of nickel. The activation energy for conduction remains constant for all compositions containing 20 mol % or less nickel. The variation of conductivity with compositions containing 1–20 mol % nickel is found to be in accordance with Wagner’s model. The decrease in conductivity of nickel oxide with the addition of 1 mol % nickel has been attributed to the trapping of holes from nickel oxide by electrons from the dispersed nickel.