Conductivity of porous Ni/ZrO/sub 2/-Y/sub 2/O/sub 3/ cermets

The conductivity of porous Ni/ZrO/sub 2-/Y/sub 2/O/sub 3/ cermets at 10000C was determined as a function of Ni content between 15 and 50 volume percent (v/o) of total solids for two different zirconia particle sizes (23 and 47 m/sup 2//g). Below Ni contents of 30 v/o, ionic conduction through the zirconia phase dominated. At 30 v/o Ni, a greater than three order of magnitude increase in the conductivity was observed, corresponding to a change in mechanism to electronic conduction through the Ni phase. The conductivity of cermets made with a Ni content greater than 30 v/o Ni was found to decrease with increasing temperature between 7000 and 10000C. While the conductivity of the cermets with the larger particle size zirconia was higher by more than a factor of four, all the samples studied had the same activation energy, 5.7 +- 0.1 kJ/mol. The increase in conductivity with zirconia particle size is attributed to improved Ni particle-to-particle contact, resulting from the Ni phase being able to cover more completely the surface of the zirconia matrix where it resides