日本金属学会誌

J. Japan Inst. Metals, Vol. 54, No. 12 (1990),
pp. 1358-1362

Tetragonal to Monoclinic Transformation in Yttria-Doped Tetragonal Zirconia Polycrystals Examined by Acoustic Microscope

Hiromichi Takebe1, Tsuneya Okano1, Takuya Semba2 and Kenji Morinaga3

1Graduate Student, Kyushu University, Kasuga, Fukuoka
2Fukuoka Institute of Technology, Wajiro, Fukuoka
3Department of Materials Science and Technology, Graduate School of Engineering Sciences, Kyushu University, Kasuga, Fukuoka

Abstract:

The tetragonal to monoclinic transformation in Y-TZP specimens and mullite/Y-TZP composites containing 5 vol% mullite, which progresses from surface to interior by annealing at 373 K in boiling water, was investigated by scanning acoustic microscope (SAM). The Rayleigh wave velocity, VR, which was measured on surfaces of the specimens, was lowered by the transformation. We obtained relationships between the transformation depth which was converted from the VR and annealing time. The depth after the annealing for 612.0 ks in the Y-TZP specimens was 7.2 μm, while in the mullite/Y-TZP composites it was less than 1.0 μm. Apparently the relationships suggested that a nucleation-growth stage existed in the process of the transformation. The transformation mechanism was discussed from changes of the transformation depth and SAM image contrast with the annealing time.


(Received 1990/5/16)

Keywords:

monoclinic, tetragonal, yttria-doped tetragonal zirconia polycrystals, transformation, acoustic microscope, water vapor, transformation depth


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