Pure zirconia and x mol% calcia partially stabilized zirconia (x = 1.5, 3, and 8) nanopowders were synthesized by hydrothermal method with various reaction temperatures for 24 hrs. The precipitated precursor of pure zirconia and x mol% calcia doped zirconia was prepared by adding NH4OH to starting solutions; resulting sample was then put into an autoclave reactor. The optimal experimental conditions, such as reaction temperatures and times and amounts of stabilizer CaO, were carefully studied. The synthesized ZrO2 and x mol% CaO-ZrO2 (x = 1.5, 3, and 8) powders were characterized by XRD, SEM, TG-DTA, and Raman spectroscopy. When the hydrothermal temperature was as low as 160˚C, pure ZrO2 and x mol% CaO-ZrO2 (x = 1.5 and 3) powders were identified as a mixture of monoclinic and tetragonal phases. However, a stable tetragonal phase of zirconia was observed in the 8 mol% calcia doped zirconia nanopowder at hydrothermal temperature above 160˚C. To observe the phase transition, the 3 mol% CaO-ZrO2 and 8 mol% CaO-ZrO2 nanopowders were heat treated from 600 to 1000˚C for 2h. The 3 mol% CaO-ZrO2 heat treated at above 1000˚C was found to undergo a complete phase transition from mixture phase to monoclinic phase. However, the 8 mol% calcia doped zirconia appeared in the stable tetragonal phase after heat treatment. The result of this study therefore should be considered as the preparation of 8 mol% CaO-ZrO2 nanopowders via the hydrothermal method.

산소이온전도체 13mol% CaO안정화 ZrO2에 대한 AI2O3의 첨가효과를 살펴보기 위해 출발원료분말을 (Zr0.87 Ca0.13 O1.871-x AI2O3)x,(x=0,0.01,0.02,0.03,0.05)와 같은 조성이 되도록 공침법으로 합성하고 1400˚C에서 소결시켜, AI2O3의 첨가에 따른 /grain size의 변화, AI2O3의 형태 및 존재위치, 소결밀도의 변화, 그리고 저항률의 변화를 살펴보았다. 그 결과, 결정립의 크기는 1mol% A I2O3첨가까지는 증가하였고, 2mol%첨가이상에서는 입계로 석출하기 시작한 AI2O3의 pinning효과에 기인되어 감소하였다. 또 1mol% AI2O3첨가시에 격자상수값의 급격한 감소가 보여지고, 그 이상에서는 변화가 별로 없어 13mol%CaO안정화 ZnO2의 고용도한은 최대 1mol%임을 알 수 있었다. 전기전도도 또한 1mol% AI2O3첨가시에 증가됨을 나타냈다. ZrO2에의 고용도한까지의 AI2O3첨가는 결정립성장을 촉진시키며 밀도값의 증대를 가져오고 전기전도도의 증가를 가져오는 긍정적인 효과를 나타냈다.