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Home  >  Journal list  >  Journal of the Ceramic Society of Japan ( 2003 - 2007 )  >  Vol.114  No.1327 (March) (2006)  >  pp.230-237

Journal of the Ceramic Society of Japan ( 2003 - 2007 )
<<Previous article Vol.114  No.1327 (March) (2006)   pp.230 - 237 Next article>>

Grain Boundary Segregation-Induced Phase Transformation in Yttria-Stabilized Tetragonal Zirconia Polycrystal

Koji MATSUI1), Nobukatsu OHMICHI1), Michiharu OHGAI1), Hidehiro YOSHIDA2) and Yuichi IKUHARA3)
1) Synthetic Chemicals Production, Tosoh Corporation
2) National Institute for Materials Science
3) Institute of Engineering Innovation, School of Engineering, The University of Tokyo


  The microstructure in 2.9 mol% Y2O3-stabilized tetragonal zirconia polycrystal (Y-TZP) sintered at 1100°-1650°C was examined to clarify the role of Y3+ ions on the cubic-formation and grain growth processes. The cubic phase in Y-TZP stared to appear at 1300°C and the fraction of the cubic phase increased with the increasing sintering temperature. Scanning transmission electron microscopy and nanoprobe X-ray energy dispersive spectroscopy (EDS) measurements revealed that the Y3+ ion distribution in the grain interiors in Y-TZP was nearly homogeneous up to 1300°C and cubic phase regions in the grain interiors were formed clearly over 1300°C. The cubic phase region in the grain interior was extended as the sintering temperature increased. High-resolution electron microscopy and nanoprobe EDS measurements revealed that no amorphous layer existed along the grain-boundary faces in Y-TZP, and Y3+ ions segregated at their grain boundaries over a width of ~10 nm. The segregation peak of Y3+ ions was clearly seen at 1300°C, and above this temperature, Y3+ ions segregated at the grain boundaries not only between tetragonal grains but also between tetragonal and cubic grains. These results show that cubic phase regions started to be transformed from the grain boundaries and/or the triple junctions in which Y3+ ions segregated. The cubic-formation mechanism in Y-TZP can be reasonably explained from the viewpoint of the Grain Boundary Segregation-Induced Phase Transformation model, and the grain-growth behavior is probably controlled by the solute drag effect of Y3+ ions segregating along the grain boundary.



Keyword:
Tetragonal zirconia polycrystal, Grain boundary segregation-induced phase transformation, Sintering, Microstructure, Grain growth

Received: October 18, 2005
Accepted: January 19, 2006 , Published online: March 01, 2006
Copyright (c) 2006 The Ceramic Society of Japan

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