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Effect of MgO Solute on Microstructure Development in Al 2 O 3
Author(s) -
BERRY K. A.,
HARMER M. P.
Publication year - 1986
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.1151-2916.1986.tb04719.x
Subject(s) - sintering , grain boundary diffusion coefficient , grain growth , materials science , solvent drag , grain size , diffusion , microstructure , effective diffusion coefficient , growth rate , surface diffusion , grain boundary , metallurgy , magnesium , mineralogy , chemistry , thermodynamics , mathematics , medicine , physics , geometry , radiology , adsorption , magnetic resonance imaging
The effect of MgO as a solid‐solution additive in the sintering of Al 2 O 3 was studied. The separate effects of the additive on densification and grain growth were assessed. Magnesia was found to increase the densification rate during sintering by a factor of 3 through a raising of the diffusion rate. The grain‐size dependence of the densification rate indicated control primarily by grain‐boundary diffusion. Magnesia also increased the grain growth rate during sintering by a factor of 2.5. The dependence of the grain growth rate on density and grain size suggested a mechanism of surface‐diffusion‐controlled pore drag. It was argued, therefore, that MgO enhanced grain growth by raising the surface diffusion coefficient. The effect of MgO on the densification rate/grain growth rate ratio was, therefore, found to be minimal and, consequently, MgO did not have a significant effect on the grain size/density trajectory during sintering. The role of MgO in the sintering of alumina was attributed mainly to its ability to lower the grain‐boundary mobility.