Final Sintering of Cr₂O₃
The effect of oxygen activity on the sintering of high-purity Cr₂O₃ is shown. Theoretical density was approached at the equilibrium O₂ partial pressure needed to maintain the Cr₂O₃ phase (Po2=2×10−12 atm). The presence of N₂ 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 O₂ activity, correlated with the changing predominant volatile species in the Cr-O system.
P. D. Ownby and G. E. Jungquist, "Final Sintering of Cr₂O₃," Journal of the American Ceramic Society, American Ceramic Society, Sep 1972.
The definitive version is available at https://doi.org/10.1111/j.1151-2916.1972.tb11334.x
Materials Science and Engineering
Article - Journal
© 1972 American Ceramic Society, All rights reserved.