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Visible Light Transparency for Polycrystalline Ceramics of MgO ·2 Al 2 O 3 and MgO ·2.5 Al 2 O 3 Spinel Solid Solutions
Author(s) -
Sutorik Anthony C.,
Cooper Christopher,
Gilde Gary
Publication year - 2013
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/jace.12636
Subject(s) - spinel , materials science , crystallite , sintering , ceramic , cordierite , mineralogy , calcination , composite material , metallurgy , chemistry , biochemistry , catalysis
Magnesium aluminate spinel solid solutions with the alumina‐rich compositions MgO ·2 Al 2 O 3 and MgO ·2.5 Al 2 O 3 have been prepared as polycrystalline ceramics with average in‐line transmissions at 550 nm of 85.5 ± 0.3% and 80.9 ± 0.4%, respectively. Starting powders are prepared from combinations of high purity Mg ( OH ) 2 and γ‐ Al 2 O 3 thoroughly mixed in an aqueous slurry, and the solids are collected, dried, calcined, mixed with LiF sintering aid, and sieved. The optimum amount of LiF added varies with the alumina composition of the spinel solid solution. The powders are sintered into dense ceramics by hot pressing at 1600°C under vacuum and 20 MPa uniaxial load followed by hot isostatic pressing at 1850°C under 200 MPa in Ar . Both compositions exhibit exaggerated grain growth with average sizes well over 500 μm. Knoop hardness measurements are 11.2 ± 0.3 GPa for MgO ·2 Al 2 O 3 and 11.0 ± 0.4 GPa for MgO ·2.5 Al 2 O 3 .