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A new high‐pressure strontium germanate, SrGe 2 O 5
Author(s) -
Nakatsuka Akihiko,
Sugiyama Kazumasa,
Ohkawa Makio,
Ohtaka Osamu,
Fujiwara Keiko,
Yoshiasa Akira
Publication year - 2016
Publication title -
acta crystallographica section c
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.304
H-Index - 17
ISSN - 2053-2296
DOI - 10.1107/s205322961601353x
Subject(s) - germanate , isostructural , strontium , octahedron , crystallography , perovskite (structure) , materials science , alkaline earth metal , crystal structure , bismuth germanate , phase (matter) , germanium , crystal chemistry , mineralogy , chemistry , metal , physics , metallurgy , doping , optics , silicon , scintillator , optoelectronics , organic chemistry , detector
The Sr–Ge–O system has an earth‐scientific importance as a potentially good low‐pressure analog of the Ca–Si–O system, one of the major components in the constituent minerals of the Earth's crust and mantle. However, it is one of the germanate systems that has not yet been fully examined in the phase relations and structural properties. The recent findings that the SrGeO 3 high‐pressure perovskite phase is the first Ge‐based transparent electronic conductor make the Sr–Ge–O system interesting in the field of materials science. In the present study, we have revealed the existence of a new high‐pressure strontium germanate, SrGe 2 O 5 . Single crystals of this compound crystallized as a co‐existent phase with SrGeO 3 perovskite single crystals in the sample recovered in the compression experiment of SrGeO 3 pseudowollastonite conducted at 6 GPa and 1223 K. The crystal structure consists of germanium–oxygen framework layers stacked along [001], with Sr atoms located at the 12‐coordinated cuboctahedral site; the layers are formed by the corner linkages between GeO 6 octahedra and between GeO 6 octahedra and GeO 4 tetrahedra. The present SrGe 2 O 5 is thus isostructural with the high‐pressure phases of SrSi 2 O 5 and BaGe 2 O 5 . Comparison of these three compounds leads to the conclusion that the structural responses of the GeO 6 and GeO 4 polyhedra to cation substitution at the Sr site are much less than that of the SrO 12 cuboctahedron to cation substitution at the Ge sites. Such a difference in the structural response is closely related to the bonding nature.