J. Japan Inst. Metals, Vol. 68, No. 7 (2004),
pp. 427-431

Small Dopant Effect on Static Grain Growth and Flow Stress in Superplastic TZP

Hidehiro Yoshida^1,, Hitoshi Nagayama² and Taketo Sakuma²

Abstract:

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.

(Received 2004/3/15)

Keywords:

grain growth, superplasticity, tetragonal zirconia polycrystal, dopant effect

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