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Abnormal Grain Growth in Alumina: Synergistic Effects of Yttria and Silica
Author(s) -
MacLaren Ian,
Can Rowland M.,
Gülgün Mehmet A.,
Voytovych Rayisa,
PopescuPogrion Nicoletta,
Scheu Christina,
Täffner Ulrike,
Rühle Manfred
Publication year - 2003
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.2003.tb03354.x
Subject(s) - grain boundary , faceting , sintering , materials science , yttria stabilized zirconia , high resolution transmission electron microscopy , doping , impurity , microstructure , grain growth , anisotropy , mineralogy , chemical engineering , crystallography , composite material , cubic zirconia , nanotechnology , transmission electron microscopy , chemistry , ceramic , optics , optoelectronics , physics , organic chemistry , engineering
Abnormal grain growth without strong anisotropy or faceting of the grains has been observed in high‐purity yttria‐doped alumina specimens, often starting at the surface and spreading right through the bulk at higher sintering temperatures. This appears to occur because of an interaction between Si contamination from sintering and the yttria doping; no such effect is seen for undoped samples. Similar microstructures were observed after deliberate Y/Si codoping. Analytical STEM showed that some grain boundaries bordering on large grains contained more Si than Y. HRTEM and diffuse dark‐field imaging revealed thin (0.5–0.9 nm) disordered layers at some boundaries bordering large grains. It appears that Si impurities are accumulating at some boundaries and together with the Y inducing a grain boundary structural transformation that accounts for the dramatically increased mobility of these boundaries.