Influence of α-Al2O3 addition on sintering and grain growth behaviour of 8 mol% Y2O3-stabilised cubic zirconia (c-ZrO2)

The effect of α-Al2O3 addition on sintering and grain growth behaviour of high purity 8 mol% yttria-stabilised cubic zirconia (c-ZrO2) was investigated. For these purposes, 1 wt.% α-Al2O3 was selected as a dopant in c-ZrO2. The slip-cast specimens were sintered at different temperatures between 1150 and 1400 °C. It was seen that doped c-ZrO2 had a faster sintering rate and lower sintering temperature than undoped c-ZrO2. In particular, doped c-ZrO2 achieved a density of 95% of its theoretical value at 1275 °C, while undoped c-ZrO2 reached the same value at 1325 °C. The different sinterability of doped c-ZrO2 and undoped c-ZrO2 can be attributed to their different behaviour of grain growth. For grain growth measurements, the specimens sintered at 1400 °C were annealed at 1400, 1500 and 1600 °C for 10, 30 and 66 h. It was seen that grain growth rate could be controlled by the deliberate addition of 1 wt.% grain boundary phase of α-Al2O3. A grain growth exponent of 2 and activation energy for grain growth of 298 kJ/mol were obtained for undoped c-ZrO2. The α-Al2O3 containing specimens had a grain growth exponent of 3 and activation energy of 361 kJ/mol. The slow grain growth in doped c-ZrO2 is attributed to solute ions segregation in grain boundary region. The addition of the grain boundary phase results in limiting matter transfer along the grain boundary resulting in slower grain growth.