Glass formation and structure in the MgSiO{sub 3}-Mg{sub 2}SiO{sub 4} pseudobinary system: From degraded networks to ioniclike glasses

Journal Article · Mon Sep 21 00:00:00 EDT 2009 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.3225431· OSTI ID:21559776

Kalampounias, A G ^[1]; Nasikas, N K ^[1]; Papatheodorou, G N ^[1]

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1. Institute of Chemical Engineering and High Temperature Chemical Processes, FORTH, P.O. Box 1414, GR-26504 Patras (Greece)

A series of glasses xMgO-(1-x)SiO{sub 2} with compositions from enstatite MgSiO{sub 3} (x=0.5) to forsterite Mg{sub 2}SiO{sub 4} (x=0.667) in mole fraction intervals of x{approx_equal}0.02 have been prepared by containerless levitation techniques and CO{sub 2} laser heating. Polarized and depolarized Raman spectra measured at ambient conditions for all these glasses show systematic and smooth band intensity changes with composition. Analysis of the Raman band contours in terms of vibrations due to different oxygen bridged SiO{sub 4} tetrahedra (Q{sup i}, species analysis) undoubtedly shows that bridging oxygens are present in all glasses studied even in the limit of the forsterite composition where bridged Si{sub 2}O{sub 7}{sup 6-} ionic dimers are formed. Furthermore the relative amounts of the Q{sup i} species change smoothly with composition while at high MgO content 'free' oxygens are present presumably forming Mg-O-Mg bridges, which contribute to the glass stability at these compositions. Raman spectra measurements at different temperature below T{sub g} show small alterations in the Q{sup i} species in the MgSiO{sub 3} region while no changes were observed in the Mg{sub 2}SiO{sub 4} region. The Boson peak frequency is practically invariant on both composition and temperature and this is in contrast to the systematics followed by most silicate glasses. It is suggested that at compositions near the forsterite ioniclike glasses are formed arising from a very fragile liquid.

• OSTI ID: 21559776
• Journal Information: Journal of Chemical Physics, Vol. 131, Issue 11; Other Information: DOI: 10.1063/1.3225431; (c) 2009 American Institute of Physics; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CARBON DIOXIDE LASERS
DIMERS
ENSTATITE
GLASS
HEATING
MAGNESIUM OXIDES
MAGNESIUM SILICATES
OXYGEN
PEAKS
RAMAN SPECTRA
SILICA
SILICON OXIDES
STABILITY
ALKALINE EARTH METAL COMPOUNDS
CHALCOGENIDES
ELEMENTS
GAS LASERS
LASERS
MAGNESIUM COMPOUNDS
MINERALS
NONMETALS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
SPECTRA