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Structural Disorder and Intracrystalline Microtexture of α′ H ‐(Ba 0.24 Ca 0.76 ) 2 SiO 4
Author(s) -
Fukuda Koichiro,
Hasegawa Hajime,
Iwata Tomoyuki,
Hashimoto Shinobu,
Inoue Koji
Publication year - 2007
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.1551-2916.2007.01493.x
Subject(s) - orthorhombic crystal system , isostructural , crystallography , crystal structure , crystal (programming language) , materials science , crystal twinning , atom (system on chip) , space group , x ray crystallography , diffraction , chemistry , optics , microstructure , physics , programming language , embedded system , computer science
The structural disorder and twin microtexture of (Ba 0.24 Ca 0.76 ) 2 SiO 4 crystal were investigated by X‐ray powder diffraction, precession method, and optical microscopy. The crystal at 298 K was orthorhombic (space group Pnma , Z =4) with a =0.70490(5) nm, b =0.55399(4) nm, c =0.95532(7) nm, and V =0.37306(4) nm 3 . The crystal structure was satisfactorily described by a split‐atom model, involving the positional disorder of Ba/Ca and O atoms across the (010) mirror plane. The crystal was found to be isostructural with α′ H ‐Ca 2 SiO 4 , thus regarded as the stabilized α′ H phase. The crystal grain was composed of orthorhombic domains in three different orientations. The unit cells within each domain were related to one another by the threefold pseudo‐symmetry axis lost during the α‐to‐α′ H transition. Each domain was most probably made up of sub‐domains of the two mirror‐related structural configurations with P 2 1 / n symmetry.