Phase transition and electrical conductivity of scandia-stabilized zirconia prepared by spark plasma sintering process

It has been attempted to suppress cubic–rhombic phase transition of 12SSZ for eliminating a discontinuity in electrical conductivity by making crystallite size finer without resorting to the conventional method of doping with heterogeneous element. Synthesized powder was prepared by the citrate process, and sintered through the SPS method, where the specimen was sintered at lower temperatures with grain growth suppressed. Synthesized powder presented cubic phase with crystallite size about 340 Å. The SPS method provides dense-sintered specimen of cubic phase at the room temperatures after having been sintered at temperatures lower than 1100 °C, with crystallite size around 370 Å, while that of air-sintered at 1500 °C is as large as 650 Å. The electrical conductivity of SPS specimen increased in the lower temperature range (400–670 °C), while decreased in the higher range (680–800 °C), in contrast to air-sintered specimen. When the transition point was lowered close to the room temperature, the discontinuity in conductivity at around 670–680 °C was eliminated.