日本金属学会誌

J. Japan Inst. Metals, Vol. 69, No. 9 (2005),
pp. 831-834

GeO2-Doping Dependence of High Temperature Superplastic Behavior in 3Y-TZP

Hidehiro Yoshida, Kenji Nakatani, Hitoshi Nagayama, Takahisa Yamamoto and Taketo Sakuma

School of Frontier Science, The University of Tokyo, Tokyo 113-8656

Abstract:

Superplastic behavior in a fine-grained, GeO2-doped 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) with the dopant level of 0.2 to 3 mol% was examined at 1400°C under an initial strain rate of 1.3 × 10-4 s-1. Microstructure and chemical composition at the grain boundaries were examined by high-resolution transmission electron microscopy (HRTEM) combined with an X-ray energy dispersive spectrometer (EDS). No secondary phase was observed along the grain boundaries, though EDS analysis indicated the segregation of Ge cations along the grain boundaries. The Ge content at the grain boundaries tends to increase with increasing the total amount of GeO2 addition, but saturate over the doping level of 2 mol%. Dependence of flow stress reduction on the total amount of GeO2 addition has a good correlation with Ge content at the grain boundaries. This fact indicates that the GeO2-doping effect on the flow stress in 3Y-TZP is caused mainly from the grain boundary segregation of Ge cations.


(Received 2005/6/2)

Keywords:

tetragonal zirconia polycrystal, superplasticity, grain boundary segregation, transmission electron microscopy


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