Far-infrared spectra of alkali germanate glasses and correlation with electrical conductivity

Journal Article · Tue Oct 01 04:00:00 EDT 1996 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.54.9775· OSTI ID:385704

Kamitsos, E I; Yiannopoulos, Y D ^[1]; Jain, H; Huang, W C ^[2]

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1. Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vass. Constantinou Ave., Athens 116 35 (Greece)
2. Department of Materials Science and Engineering, Lehigh University, Bethlehem, Pennsylvania 18015 (United States)

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.}

• OSTI ID: 385704
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 14 Vol. 54; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ACTIVATION ENERGY
CESIUM OXIDES
ELECTRIC CONDUCTIVITY
FAR INFRARED RADIATION
GERMANIUM OXIDES
GLASS
INFRARED SPECTRA
LITHIUM OXIDES
POTASSIUM OXIDES
RUBIDIUM OXIDES
SHORT-RANGE ORDER
SODIUM OXIDES
TEMPERATURE DEPENDENCE
VIBRATIONAL STATES