start-ver=1.4
cd-journal=joma
no-vol=134
cd-vols=
no-issue=1
article-no=
start-page=1
end-page=4
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=2026
dt-pub=20260101
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=
kn-title=Structural and spectroscopic characterization of keatite (SiO2)
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract=Keatite, a polymorph of silica rare in nature, was synthesized by hydrothermal treatment of silicon and water at 100 MPa and 600 ��C. The crystal structure of keatite at 24 ��C was refined by the Rietveld method using synchrotron X-ray diffraction data. The obtained structure is consistent with the results of previous studies in which some constraints were imposed during refinements. The 29Si MAS NMR spectrum of keatite shows two peaks at ?113.9 and ?114.3 ppm, which can be assigned to Si at the Si1 and Si2 sites, respectively. The Raman spectrum of keatite shows a prominent peak at 473 cm?1, which is attributable to the Si?O?Si bending mode of the 5-membered ring. These spectra, reported for the first time, are expected to be valuable for the identification of keatite in synthetic and natural samples.
en-copyright=
kn-copyright=

en-aut-name=KanzakiMasami
en-aut-sei=Kanzaki
en-aut-mei=Masami
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=1
ORCID=

en-aut-name=XueXianyu
en-aut-sei=Xue
en-aut-mei=Xianyu
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=2
ORCID=

affil-num=1
en-affil=Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=2
en-affil=Institute for Planetary Materials, Okayama University
kn-affil=
en-keyword=SiO2
kn-keyword=SiO2
en-keyword=Keatite
kn-keyword=Keatite
en-keyword=Crystal structure
kn-keyword=Crystal structure
en-keyword=Raman spectroscopy
kn-keyword=Raman spectroscopy
en-keyword=NMR spectroscopy
kn-keyword=NMR spectroscopy
END

start-ver=1.4
cd-journal=joma
no-vol=128
cd-vols=
no-issue=10
article-no=
start-page=843
end-page=846
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=2020
dt-pub=2020101
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=
kn-title=Crystal structure of Ca(Fe0.4Si0.6)O2.8 oxygen-deficient perovskite
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract=The crystal structure of Ca(Fe3+0.4Si0.6)O2.8 oxygen-deficient perovskite phase synthesized at 12 GPa and 1400 ��C was studied using synchrotron powder X-ray diffraction. The phase is isostructural to low-pressure phase of Ca(Al0.4Si0.6)O2.8. The structure was refined by the Rietveld method and is consists of a perovskite-like triple-layer of corner-shared (Fe3+,Si)O6 octahedra and a double-layer of SiO4 tetrahedra those are stacked alternatively in the [111] direction of ideal cubic perovskite. Small degree of Fe3+/Si disorder was detected between two octahedral sites. The structure is compared with other oxygen-deficient perovskites.
en-copyright=
kn-copyright=

en-aut-name=KanzakiMasami
en-aut-sei=Kanzaki
en-aut-mei=Masami
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=1
ORCID=

affil-num=1
en-affil=Institute for Planetary Materials, Okayama University
kn-affil=
en-keyword=Crystal structure
kn-keyword=Crystal structure
en-keyword=Rietveld refinement
kn-keyword=Rietveld refinement
en-keyword=Oxygen-deficient perovskite
kn-keyword=Oxygen-deficient perovskite
en-keyword=High-pressure silicate
kn-keyword=High-pressure silicate
END