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Final Sintering of Cr 2 O 3
Author(s) -
OWNBY P. D.,
JUNGQUIST G. E.
Publication year - 1972
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.1151-2916.1972.tb11334.x
Subject(s) - sintering , spinel , nucleation , materials science , grain boundary , partial pressure , grain growth , phase (matter) , metallurgy , magnesium , oxide , oxygen , oxygen pressure , mineralogy , microstructure , thermodynamics , chemistry , physics , organic chemistry
The effect of oxygen activity on the sintering of high‐purity Cr 2 O 3 is shown. Theoretical density was approached at the equilibrium O 2 partial pressure needed to maintain the Cr 2 O 3 phase ( P o2 =2×10 −12 atm). The presence of N 2 in the atmosphere during sintering did not prevent final sintering. The addition of 0.1 wt% MgO at this equilibrium pressure effectively controlled the grain growth and further increased the sintered density to very near the theoretical value. The solute segregation of MgO at the grain boundaries, followed by nucleation of spherulites of magnesium chromite spinel on the boundaries, accounted for the grain‐growth control. It is speculated that these isolated spherulites locked the grain boundaries together, changing the fracture mode of the sintered oxide from inter‐to intragranular and also that larger MgO additions produced a more continuous spinel formation at the boundaries, resulting in decreased sintered density. Weight loss, which was also monitored as a function of O 2 activity, correlated with the changing predominant volatile species in the Cr‐O system.