On the glass transition and viscosity of P2O5

S. W. Martin, Charles Angell

Research output: Contribution to journalArticle

45 Citations (Scopus)

Abstract

The calorimetric glass transition temperature Tg for pure anhydrous P2O5 melted in sealed SiO2 ampules at 1000°C has been obtained directly for the first time with differential scanning calorimetry, and the increase in heat capacity at Tg has been determined. Tg measured in this way is 57 K higher than the value quoted in the literature, which is probably based on an Arrhenius law extrapolation of viscosity data to η = 1013 P. Combining the high-temperature viscosity data with the common observation that, for oxide glasses, η = 1012 P at the DSC Tg, we find that the P2O5 viscosity obeys an Arrhenius law over at least 6 decades of η. Furthermore, the intercept at 1/T = 0 coincides with the common point of Tg-reduced viscosity plots for a wide variety of liquids recently used in establishing the "strong" vs. "fragile" classification of glass-forming liquids. On this basis, P2O5 behaves as the archetypal "strong" liquid. However, the value of Cp(liquid)/Cp(glass) at Tg, 1.27, is larger than expected on this basis since other "strong" liquids show smaller values, e.g., GeO2 (1.09) and BeF2 (no ΔCp detected). The dependence of Tg on heating rate has been determined and shows that enthalpy relaxation in the transition region has, within error, the same activation energy (43.9 kcal/mol) as for viscous flow.

Original languageEnglish (US)
Pages (from-to)6736-6740
Number of pages5
JournalJournal of Physical Chemistry
Volume90
Issue number25
StatePublished - 1986
Externally publishedYes

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phosphorus pentoxide
Glass transition
Viscosity
viscosity
glass
Liquids
liquids
Glass
viscous flow
Viscous flow
Heating rate
Extrapolation
Oxides
glass transition temperature
Specific heat
extrapolation
Differential scanning calorimetry
Enthalpy
heat measurement
Activation energy

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

On the glass transition and viscosity of P2O5 . / Martin, S. W.; Angell, Charles.

In: Journal of Physical Chemistry, Vol. 90, No. 25, 1986, p. 6736-6740.

Research output: Contribution to journalArticle

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