Effect of P in ZrO2 raw material on ionic conductivity and thermal shock resistance of yttria-stabilized zirconia

Starting materials of ZrO2 ? 0 ppm-P, 140 ppm-P and 600 ppm-P were prepared using high-purity ZrO2 and NH4H2PO4. Using Y2O3 as a stabilizer, (ZrO2)0.95(Y2O3)0.05 ceramics were fabricated at a sintering temperature of 1400-1600 ℃. The crystal phase consisted of tetragonal and cubic systems. There was no significant difference in conductivity among the ceramics sintered above 1500℃. In the ceramics sintered at 1400 ℃, the conductivity increased in the order of ZrO2 ? 0 ppm-P, ZrO2 ? 140 ppm-P, ZrO2 ? 600 ppm-P. In ceramics sintered at 1450 ℃, ZrO2 ? 600 ppm-P showed higher conductivity than ZrO2 ? 0 ppm-P and ZrO2 ? 140 ppm-P. In the Nyquist plot of ceramics sintered at 1450 ℃, the circular arc caused by the grain boundary resistance component decreased in the order of ZrO2 ? 0 ppm-P, ZrO2 ? 140 ppm-P, ZrO2 ? 600 ppm-P. It is considered that as the P content in the ZrO2 raw material increased, the ceramics were easily sintered and the pores decreased. In the thermal shock resistance test, cracks were confirmed in all ceramics sintered at 1450°C or higher. In ceramics sintered at 1400℃, ZrO2 ? 0 ppm-P and ZrO2 ? 140 ppm-P had high thermal shock resistance and were almost equivalent. Therefore, ceramics fabricated from ZrO2 ? 140 ppm-P at 1400 ℃ were excellent in both ionic conductivity and thermal shock resistance.