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Solubility of Magnesia in Polycrystalline Alumina at High Temperatures
Author(s) -
Greskovich C.,
Brewer J. Anthony
Publication year - 2001
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.1151-2916.2001.tb00671.x
Subject(s) - solubility , sintering , grain growth , materials science , crystallite , impurity , doping , grain boundary , enthalpy , grain size , magnesium , solid solution , phase (matter) , analytical chemistry (journal) , mineralogy , chemical engineering , metallurgy , microstructure , thermodynamics , chemistry , chromatography , organic chemistry , physics , optoelectronics , engineering
High‐purity Al 2 O 3 compacts were doped with 0–350 ppm (by weight) of MgO using a liquid immersion technique and equilibrated at temperatures between 1700° and 2000°C under hydrogen. The solubility limits of MgO in Al 2 O 3 at temperatures of 1720° and 1880°C were very low, ∼75 and 175 ppm, respectively. Variation of MgO solubility with temperature could be represented by the equation, ln Mg/Al = 3.80–2.63 × 10 4 / T . The small MgO solubilities were understood by the high enthalpy (326 kJ/mol) of solution. The results of this study suggested that previous investigations on sintering and grain‐growth mechanisms in MgO‐doped Al 2 O 3 were probably not done in single‐phase Al 2 O 3 solid solutions. However, the conclusions on sintering and grain‐growth mechanisms in prior research work in MgO‐doped A 2 O 3 may be correct. The effects of SiO 2 impurity and grain size on MgO solubility are discussed. Previous grain‐growth experiments in MgO‐doped Al 2 O 3 are described that demonstrate the clearest evidence for grain‐boundary mobility controlled by a solid‐solution mechanism.