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Transparent Solid Solution Magnesium Aluminate Spinel Polycrystalline Ceramic with the Alumina‐Rich Composition MgO ·1.2 Al 2 O 3
Author(s) -
Sutorik Anthony C.,
Gilde Gary,
Swab Jeffrey J.,
Cooper Christopher,
Gamble Robert,
Shanholtz Eugene
Publication year - 2012
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.1551-2916.2011.04798.x
Subject(s) - spinel , materials science , crystallite , sintering , ceramic , calcination , aluminate , magnesium , mineralogy , flexural strength , cordierite , solid solution , chemical engineering , analytical chemistry (journal) , metallurgy , composite material , chemistry , cement , chromatography , biochemistry , catalysis , engineering
Solid solution magnesium aluminate spinel with the alumina‐rich composition MgO ·1.2 Al 2 O 3 has been prepared as a transparent polycrystalline ceramic with average in‐line transmission at 550 nm of 84.8 ± 2.7% and >82% throughout the visible spectrum. Starting powders are prepared from mixtures of high purity Mg(OH) 2 and γ‐Al 2 O 3 thoroughly mixed in an aqueous slurry. Water is removed by rotary evaporation. The solids are collected, dried, calcined, mixed with LiF (as a sintering aid), and sieved. 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 Ar . Final grain sizes ranged between 300 and 1000 μm. Samples exhibited flexural strength of 176.8 ± 46.2 MPa; hardness of 12.3 ± 0.2 GPa; and elastic modulus of 292.9 ± 7.5 GPa. Control samples of stoichiometric magnesium aluminate spinel ( MgO · Al 2 O 3 ) were prepared with the same procedure and exhibited comparable values for transmission and physical properties.