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Raman band assignments of silicate and germanate glasses using high‐pressure and high‐temperature spectral data
Author(s) -
Sharma Shiv K.,
Cooney Thomas F.,
Wang Zifu,
van der Laan Sieger
Publication year - 1997
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/(sici)1097-4555(199709)28:9<697::aid-jrs162>3.0.co;2-k
Subject(s) - germanate , raman spectroscopy , silicate , spectral line , albite , analytical chemistry (journal) , chemistry , deuterium , crystallography , materials science , optics , physics , atomic physics , quartz , organic chemistry , ion , chromatography , astronomy , composite material
The assignments of Raman bands in the spectra of silicate and germanate glasses, including SiO 2 , GeO 2 , Rb 2 Si 4 O 9 , NaFe 3+ Si 3 O 8 , anhydrous and hydrous albite (NaAlSi 3 O 8 ) and anhydrous and deuterated Ge‐albite (NaAlGe 3 O 8 ) and Ge‐jadeite (NaAlGe 2 O 6 ), were re‐examined in the light of new information from Raman measurements at high pressures and temperatures. On the basis of polarized Raman spectra of single‐component (e.g. SiO 2 and GeO 2 ) glasses, it is demonstrated that the ν as (T–O–T) mode (where T represents tetrahedrally coordinated cations, Si or Ge) gives rise to LO–TO splitting. The depolarized nature of the ν as (T–O–T) LO–TO doublet in the Raman spectra of SiO 2 and GeO 2 glasses reflects the fact that the local site symmetry of T cations is close to T d . Persistence of the ν as (T–O–T) LO–TO doublet slightly above the melting temperature demonstrates that significant intermediate range order exists even in the high‐temperature liquids. Likewise, in the spectra of NaFe 3+ Si 3 O 8 and NaFe 3+ Si 2 O 6 glasses, the high‐wavenumber ν as (T–O–T) bands exhibit a depolarized character characteristic of a three‐dimensional network. The depolarized nature of the ν as (T–O–T) bands indicates that the local site symmetry of the T cation is close to T d and that the triply degenerate ( F ) character of the ν as (T–O–T) is preserved. Additionally, a significant shift in the position of the ν as (T–O–T) mode on substituting NaFe 3+ for Si 4‐ reflects strong vibrational coupling of FeO 4 and SiO 4 tetrahedra in the glass. In the hydrated and deuterated aluminosilicate and ‐germanate glasses, it is proposed that the degeneracy of the ν as (T–O–T) bands is lifted because of structural distortion caused by the presence of H 3 O + (D 3 O + ) ions. © 1997 John Wiley & Sons, Ltd.