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Effects of Chemical Inhomogeneities on Grain Growth and Microstructure in Al 2 O 3
Author(s) -
Handwerker Carol A.,
Morris Patricia A.,
Coble Robert L.
Publication year - 1989
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.1151-2916.1989.tb05965.x
Subject(s) - impurity , materials science , grain boundary , grain growth , microstructure , sintering , dihedral angle , mineralogy , analytical chemistry (journal) , doping , grain boundary diffusion coefficient , abnormal grain growth , grain size , crystallography , metallurgy , chemistry , chromatography , hydrogen bond , optoelectronics , organic chemistry , molecule
Effects of chemical inhomogeneities and single‐crystal seeds on normal and discontinuous grain growth were investigated in both undoped and MgO‐doped Al 2 O 3 . The chemical impurities in the samples were exsolved at a lower temperature than the sintering temperature and measured by SEM/EDS to determine the correlation between the distribution of impurities and the microstructure in Al 2 O 3 . A feature of this study was the use of clean‐room processing and firing procedures to maintain sample composition at the levels initially present in the starting powders. As the local concentrations of chemical impurities (i.e., Si, Ca) increased, the grain boundary–grain boundary dihedral angle distribution widened, with many angles at 180°, the grain‐size distribution widened, and pore–boundary separation was enhanced. Discontinuous grain growth was observed in regions of undoped Al 2 O 3 containing the largest Ca and Si concentrations. It is suggested that doping with MgO solute reduces the effects of impurities on grain growth by increasing the bulk solubility and decreasing interfacial segregation of impurities, especially Si, and by narrowing the distribution of grain boundary–grain boundary dihedral angles.