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Author Kamitsos, E. I. ♦ Yiannopoulos, Y. D. ♦ Jain, H. ♦ Huang, W. C.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword MATERIALS SCIENCE ♦ GLASS ♦ INFRARED SPECTRA ♦ GERMANIUM OXIDES ♦ LITHIUM OXIDES ♦ SODIUM OXIDES ♦ POTASSIUM OXIDES ♦ RUBIDIUM OXIDES ♦ CESIUM OXIDES ♦ FAR INFRARED RADIATION ♦ VIBRATIONAL STATES ♦ ELECTRIC CONDUCTIVITY ♦ TEMPERATURE DEPENDENCE ♦ ACTIVATION ENERGY ♦ SHORT-RANGE ORDER
Abstract The infrared spectra of 0.20{ital R}{sub 2}O-0.80GeO{sub 2} ({ital R}=Li,Na,K,Rb,Cs) and {ital x}Rb{sub 2}O-(1{minus}{ital x})GeO{sub 2} (0{lt}{ital x}{le}0.27) glasses were measured in the reflectance mode and analyzed by the Kramers-Kronig technique to investigate the nature and composition dependence of metal ion sites in germanate glasses. The deconvolution of the far-infrared profiles showed that in glasses of low alkali content ({ital x}{le}0.075 for {ital R}=Rb) alkali ions occupy one type of sites ({ital M}), while for higher alkali contents two types of site ({ital L} and {ital H}) were found. The ion motion frequencies in these sites are in the order {nu}{sub {ital L}}{lt}{nu}{sub {ital M}}{lt}{nu}{sub {ital H}}, and increase with increasing alkali oxide content. Factor group analysis of the alkali motion modes in analogous crystalline germanate compounds showed that the {ital H} band in glass can be assigned to ion motion in sites similar to those in the crystal. The low-frequency band ({ital L}) was attributed to ion motion in {open_quote}{open_quote}secondary{close_quote}{close_quote} energetic sites, whose coordination numbers and charge density are correspondingly larger and smaller than their optimum values. The presence of {ital L} sites is the cause of the extra absorption exhibited by glasses at low far-infrared frequencies, as compared to the crystals of similar composition. {ital M}-type sites were shown to be the precursors of {ital H} sites, but for the organization of the latter a minimum alkali oxide content is required. The comparison of activation energies for conductivity calculated on the basis of the free-ion model with observed values suggests that long-range ion movement is probably facilitated along {ital M} and {ital H}-type sites. {copyright} {ital 1996 The American Physical Society.}
ISSN 01631829
Educational Use Research
Learning Resource Type Article
Publisher Date 1996-10-01
Publisher Place United States
Journal Physical Review, B: Condensed Matter
Volume Number 54
Issue Number 14


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