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Iron and Spinel Precipitation in Iron‐Doped Sapphire
Author(s) -
Moon Anthony R.,
Phillips Matthew R.
Publication year - 1991
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.1151-2916.1991.tb06943.x
Subject(s) - spinel , precipitation , materials science , phase (matter) , sapphire , crystal (programming language) , crystallography , analytical chemistry (journal) , mineralogy , metallurgy , chemistry , laser , physics , organic chemistry , chromatography , meteorology , computer science , optics , programming language
Single crystals of Al 2 O 3 containing 0.5 wt% Fe were exposed to low p o 2 atmospheres at 1500°C to produce precipitate phases. Analytical TEM identified the precipitate phases as spinel (hercynite) and iron, with the following orientation relationships: 〈001〉 Fe ‖〈2 2 01〉 s with {1 1 0} Fe ‖{11 2 0} s , 〈111〉 Fe ‖〈10 1 0〉 s with {0 1 1} Fe ‖ (0001) s , and 〈1 1 0〉 H ‖〈01 1 0〉 s with {111} H ‖ (0001) s . The three phase fields observed — (Fe, Al) 2 O 3 , spinel +α‐Al 2 O 3 , and iron +αAl 2 O 3 — are in accordance with phase stability diagrams. Precipitation kinetics indicate that oxygen is mobile in the reduced region of the crystal.