Improvement of Mechanical Strength of 8 mol % Yttria-Stabilized Zirconia Ceramics by Spark-Plasma Sintering

Dense 8 mol % yttria-stabilized zirconia (8YSZ) ceramics consisting of submicrometer-sized grains were prepared using the spark-plasma sintering (SPS) method without any additives. The starting powder ( ca . 0.1 μm) was densified to ca . 99% of the theoretical X-ray density with shorter sintering time (5-10 min) while preserving a grain size in submicrometer. The measured three-point bending strength was ca . 400 MPa at room temperature for samples sintered at 1300°C for 5-10 min, which was higher than the value of conventionally sintered ceramics, ca . 250 MPa, due mainly to the small-grained microstructures of the SPS ceramics. The electrical conductivity was 0.19 S cm −1 at 1000°C in air, which is comparable to previously reported values ( ca . 0.1 S cm −1 ) for well-sintered ceramics. Thus, the SPS method is an effective process to improve the mechanical strength of 8YSZ without degrading the electrical conductivity.