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Characterization of quenched high pressure phases in CaSiO 3 system by XRD and 29 Si NMR
Author(s) -
Kanzaki Masami,
Stebbins Jonathan F.,
Xue Xianyu
Publication year - 1991
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/91gl00463
Subject(s) - materials science , amorphous solid , phase (matter) , nmr spectra database , octahedron , analytical chemistry (journal) , titanite , perovskite (structure) , crystallography , spectral line , bar (unit) , mineralogy , crystal structure , geology , chemistry , physics , metallurgy , chromatography , quartz , oceanography , organic chemistry , astronomy
We have studied quenched high pressure phases in the CaSiO 3 system by x‐ray diffraction (XRD) and 29 Si MAS NMR, XRD study of the previously reported “ε‐CaSiO 3 phase” synthesized at 12 GPa and 1500 °C reveals that it is actually a mixture of β‐Ca 2 SiO 4 (larnite) and a previously unknown CaSi 2 O 5 phase. This result is supported by the 29 Si NMR spectra. Furthermore, both the XRD and the NMR data suggest that the CaSi 2 O 5 phase may have a titanite (CaTiSiO 5 ) structure in which Ti is replaced by an octahedral Si. Samples quenched from 15 GPa and 1500°C consist mostly of an amorphous phase, but a small amount of CaSiO 3 ‐perovskite was identified by both XRD and NMR. The 29 si NMR spectrum of the amorphous phase suggests that its local structure is similar to that of a glass quenched from melt at 1 bar.