Hidehiro Yoshida1,, Hitoshi Nagayama2 and Taketo Sakuma2
1National Institute for Materials Science, Tsukuba 305-0047
Static grain growth behavior in 1 mol% of GeO2, TiO2, MgO or BaO-doped ZrO2-3 mol%Y2O3 (3Y-TZP) was examined at 1400°C with a special interest in dopant effect on superplastic flow stress in fine-grained 3Y-TZP. The static grain growth can be described as normal grain growth in single-phase ceramics, and the growth constant K is in the order of 10% flow stress for each material. The value of K in cation-doped TZP correlates closely to dopant cation ionic radius. Assuming that the activation energy for diffusivity of constituent ions can be given as a linear function of strain caused by the ionic size difference, the dependence of the growth constant and the flow stress on the ionic radius can be described as a function of the dopant cation ionic radius. The calculated activation energy for the diffusivity is in good agreement with the experimental data in cation-doped TZP. The small dopant effect on the flow stress can be given by the activation energy difference due to the dopant cation ionic size.
grain growth, superplasticity, tetragonal zirconia polycrystal, dopant effect
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