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Science 13 January 2006:
Vol. 311. no. 5758, pp. 212 - 215
DOI: 10.1126/science.1119839
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Reports

Grain Boundary Strengthening in Alumina by Rare Earth Impurities

J. P. Buban,1 K. Matsunaga,1* J. Chen,2 N. Shibata,1 W. Y. Ching,2 T. Yamamoto,3 Y. Ikuhara1{dagger}

Impurity doping often alters or improves the properties of materials. In alumina, grain boundaries play a key role in deformation mechanisms, particularly in the phenomenon of grain boundary sliding during creep at high temperatures. We elucidated the atomic-scale structure in alumina grain boundaries and its relationship to the suppression of creep upon doping with yttrium by using atomic resolution microscopy and high-precision calculations. We find that the yttrium segregates to very localized regions along the grain boundary and alters the local bonding environment, thereby strengthening the boundary against mechanical creep.

1 Institute of Engineering Innovation, University of Tokyo, 2-11-16, Yayoi, Bunkyo, Tokyo 113–8656, Japan.
2 Department of Physics, University of Missouri–Kansas City, 5100 Rockhill Road, Kansas City, MO 64110–2499, USA.
3 Department of Advanced Materials Science, University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba 277–8561, Japan.

* Present address: Department of Materials Science and Engineering, Kyoto University, Yoshida-Honmachi, Sakyo, Kyoto 606–8501, Japan.

{dagger} To whom correspondence should be addressed. E-mail: ikuhara{at}sigma.t.u-tokyo.ac.jp

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