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Abnormal Grain Growth of Alumina
Author(s) -
Bae IlJoon,
Baik Sunggi
Publication year - 1997
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.1151-2916.1997.tb02957.x
Subject(s) - intergranular corrosion , materials science , impurity , grain boundary , abnormal grain growth , sintering , grain growth , grain size , metallurgy , mineralogy , composite material , microstructure , chemistry , organic chemistry
Abnormal grain growth (AGG) is not one of the intrinsic properties of alumina but rather is an extrinsic property that is controlled by certain impurities that are introduced during powder synthesis, processing, or sintering. When small amounts of glass‐forming impurities are introduced, some portion beyond their solubility limits will accumulate at grain boundaries at the final stage of densification, form thin intergranular glass films of thermodynamically stable thickness, and induce the sudden appearance of abnormal grains by increasing the rate of grain‐boundary migration abruptly. The proposition has been tested experimentally with small, but varying, amounts of silica in ultrapure alumina (99.999%) that has been sintered in a contamination‐free condition. Average grain sizes for the appearance of AGG are inversely related to the doping concentration of silica. The thickness of intergranular silicate glass films at the onset of AGG in alumina is constant and estimated to be }3.7 nm.