Optical Basicity and Refractivity of Germanate Glasses

E. I. Kamitsos, Y. D. Yiannopoulos, John A Duffy

Research output: Contribution to journalArticle

34 Citations (Scopus)

Abstract

The acid-base properties of germanate glasses cannot presently be compared quantitatively with those of silicate, borate, and several other glasses because the optical basicity of the parent oxide, Delta(GeO2), has not yet been unequivocally established. The usual method of measuring optical basicity, relying on probe ions such as Tl+ or Pb2+, is prevented by the restricted ultraviolet transparency range of germanate glasses. An alternative method is used, based on refractivity data and the correlation between oxide polarizability and theoretical optical basicity known to operate in other glass systems. Data for alkali metal germanate systems (up to approximately 0.4 mole fraction alkali metal oxide) yield the value Delta(GeO2) = 0.61 and basicity moderating parameter for Ge4+, gamma, of 1.64. These values are supported by calculations based on the far-infrared "rattling" frequencies, v(eff), of alkali metal ions in germanate glasses xM(2)O-(1 - x)GeO2, M = K, Rb. The latter approach has led to the establishment of a new optical basicity scale for the germanate glasses, A = (nu(eff)/nu(0) + 1.94)/4.64, nu(0) = nu(eff)(x-->0). This new "far-infrared" basicity scale gives Delta(GeO2) = 0.63. GeO2 therefore has a basicity which is close to that of Al2O3 (Delta = 0.60) but greater than Of SiO2 (0.48). The previously established data concerning the ratio of 6-fold coordinated germanium in the K2O-GeO2, system allows calculation of gamma = 2.5 (+/-0.5) for 6-fold coordinated Ge4+.

Original languageEnglish
Pages (from-to)8988-8993
Number of pages5
JournalThe Journal of Physical Chemistry B
Volume106
DOIs
Publication statusPublished - 2002

Keywords

  • METAL-ION SITES
  • OXIDE GLASSES
  • ELECTRONIC POLARIZABILITY
  • REDOX EQUILIBRIA
  • INDEX CHANGES
  • SYSTEMS
  • FABRICATION
  • SILICATES
  • CHEMISTRY
  • SPECTRA

Cite this

Optical Basicity and Refractivity of Germanate Glasses. / Kamitsos, E. I.; Yiannopoulos, Y. D.; Duffy, John A.

In: The Journal of Physical Chemistry B, Vol. 106, 2002, p. 8988-8993.

Research output: Contribution to journalArticle

Kamitsos, E. I. ; Yiannopoulos, Y. D. ; Duffy, John A. / Optical Basicity and Refractivity of Germanate Glasses. In: The Journal of Physical Chemistry B. 2002 ; Vol. 106. pp. 8988-8993.
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abstract = "The acid-base properties of germanate glasses cannot presently be compared quantitatively with those of silicate, borate, and several other glasses because the optical basicity of the parent oxide, Delta(GeO2), has not yet been unequivocally established. The usual method of measuring optical basicity, relying on probe ions such as Tl+ or Pb2+, is prevented by the restricted ultraviolet transparency range of germanate glasses. An alternative method is used, based on refractivity data and the correlation between oxide polarizability and theoretical optical basicity known to operate in other glass systems. Data for alkali metal germanate systems (up to approximately 0.4 mole fraction alkali metal oxide) yield the value Delta(GeO2) = 0.61 and basicity moderating parameter for Ge4+, gamma, of 1.64. These values are supported by calculations based on the far-infrared {"}rattling{"} frequencies, v(eff), of alkali metal ions in germanate glasses xM(2)O-(1 - x)GeO2, M = K, Rb. The latter approach has led to the establishment of a new optical basicity scale for the germanate glasses, A = (nu(eff)/nu(0) + 1.94)/4.64, nu(0) = nu(eff)(x-->0). This new {"}far-infrared{"} basicity scale gives Delta(GeO2) = 0.63. GeO2 therefore has a basicity which is close to that of Al2O3 (Delta = 0.60) but greater than Of SiO2 (0.48). The previously established data concerning the ratio of 6-fold coordinated germanium in the K2O-GeO2, system allows calculation of gamma = 2.5 (+/-0.5) for 6-fold coordinated Ge4+.",
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T1 - Optical Basicity and Refractivity of Germanate Glasses

AU - Kamitsos, E. I.

AU - Yiannopoulos, Y. D.

AU - Duffy, John A

PY - 2002

Y1 - 2002

N2 - The acid-base properties of germanate glasses cannot presently be compared quantitatively with those of silicate, borate, and several other glasses because the optical basicity of the parent oxide, Delta(GeO2), has not yet been unequivocally established. The usual method of measuring optical basicity, relying on probe ions such as Tl+ or Pb2+, is prevented by the restricted ultraviolet transparency range of germanate glasses. An alternative method is used, based on refractivity data and the correlation between oxide polarizability and theoretical optical basicity known to operate in other glass systems. Data for alkali metal germanate systems (up to approximately 0.4 mole fraction alkali metal oxide) yield the value Delta(GeO2) = 0.61 and basicity moderating parameter for Ge4+, gamma, of 1.64. These values are supported by calculations based on the far-infrared "rattling" frequencies, v(eff), of alkali metal ions in germanate glasses xM(2)O-(1 - x)GeO2, M = K, Rb. The latter approach has led to the establishment of a new optical basicity scale for the germanate glasses, A = (nu(eff)/nu(0) + 1.94)/4.64, nu(0) = nu(eff)(x-->0). This new "far-infrared" basicity scale gives Delta(GeO2) = 0.63. GeO2 therefore has a basicity which is close to that of Al2O3 (Delta = 0.60) but greater than Of SiO2 (0.48). The previously established data concerning the ratio of 6-fold coordinated germanium in the K2O-GeO2, system allows calculation of gamma = 2.5 (+/-0.5) for 6-fold coordinated Ge4+.

AB - The acid-base properties of germanate glasses cannot presently be compared quantitatively with those of silicate, borate, and several other glasses because the optical basicity of the parent oxide, Delta(GeO2), has not yet been unequivocally established. The usual method of measuring optical basicity, relying on probe ions such as Tl+ or Pb2+, is prevented by the restricted ultraviolet transparency range of germanate glasses. An alternative method is used, based on refractivity data and the correlation between oxide polarizability and theoretical optical basicity known to operate in other glass systems. Data for alkali metal germanate systems (up to approximately 0.4 mole fraction alkali metal oxide) yield the value Delta(GeO2) = 0.61 and basicity moderating parameter for Ge4+, gamma, of 1.64. These values are supported by calculations based on the far-infrared "rattling" frequencies, v(eff), of alkali metal ions in germanate glasses xM(2)O-(1 - x)GeO2, M = K, Rb. The latter approach has led to the establishment of a new optical basicity scale for the germanate glasses, A = (nu(eff)/nu(0) + 1.94)/4.64, nu(0) = nu(eff)(x-->0). This new "far-infrared" basicity scale gives Delta(GeO2) = 0.63. GeO2 therefore has a basicity which is close to that of Al2O3 (Delta = 0.60) but greater than Of SiO2 (0.48). The previously established data concerning the ratio of 6-fold coordinated germanium in the K2O-GeO2, system allows calculation of gamma = 2.5 (+/-0.5) for 6-fold coordinated Ge4+.

KW - METAL-ION SITES

KW - OXIDE GLASSES

KW - ELECTRONIC POLARIZABILITY

KW - REDOX EQUILIBRIA

KW - INDEX CHANGES

KW - SYSTEMS

KW - FABRICATION

KW - SILICATES

KW - CHEMISTRY

KW - SPECTRA

U2 - 10.1021/jp0207230

DO - 10.1021/jp0207230

M3 - Article

VL - 106

SP - 8988

EP - 8993

JO - The Journal of Physical Chemistry B

JF - The Journal of Physical Chemistry B

SN - 1520-6106

ER -