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Hardness of polycrystalline SiO 2 coesite
Author(s) -
Kulik Eleonora,
Nishiyama Norimasa,
Higo Yuji,
Gaida Nico A.,
Katsura Tomoo
Publication year - 2019
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.16243
Subject(s) - coesite , knoop hardness test , stishovite , crystallite , materials science , indentation , quartz , fumed silica , composite material , mineralogy , indentation hardness , fused quartz , vickers hardness test , metallurgy , microstructure , chemistry , geology , paleontology , eclogite , subduction , tectonics
We measured elastic moduli and hardness of polycrystalline SiO 2 coesite. Translucent polycrystalline bulk coesite with a grain size of about 10 micrometers was fabricated at 8 GPa and 1600°C using a Kawai‐type multianvil apparatus. The obtained bulk and shear moduli are 94(1) and 60.2(3) GPa, respectively. The resulting Vickers and Knoop hardness values are 10.9(7) and 9.6(4) GPa, respectively, at an indentation load of 4.9 N. Coesite is as hard as other fourfold coordinated silica materials such as quartz and densified silica glasses. The hardness values of coesite and the fourfold coordinated silica materials are about one‐third of those of sixfold coordinated silica materials, stishovite, and seifertite, which are the hardest known oxides.