Glass transition and viscosity of P/sub 2/O/sub 5/

Journal Article · Thu Dec 04 00:00:00 EST 1986 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100283a030· OSTI ID:7032908

Martin, S W; Angell, C A

The calorimetric glass transition temperature T/sub g/ for pure anhydrous P/sub 2/O/sub 5/ melted in sealed SiO/sub 2/ ampules at 1000 /sup 0/C has been obtained directly for the first time with differential scanning calorimetry, and the increase in heat capacity at T/sub g/ has been determined. T/sub g/ 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 eta = 10/sup 13/ P. Combining the high-temperature viscosity data with the common observation that, for oxide glasses, eta = 10/sup 12/ P at the DSC T/sub g/, the authors find that the P/sub 2/O/sub 5/ viscosity obeys an Arrhenius law over at least 6 decades of eta. Furthermore, the intercept at 1/T = 0 coincides with the common point of T/sub g/ - 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, P/sub 2/O/sub 5/ behaves as the archetypal strong liquid. However, the value of C/sub p/(liquid)/C/sub p/(glass) at T/sub g/, 1.27, is larger than expected on this basis since other strong liquids show smaller values, e.g., GeO/sub 2/ (1.09) and BeF/sub 2/ (no ..delta..C/sub p/ detected). The dependence of T/sub g/ 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.

• Research Organization: Purdue Univ., West Lafayette, IN
• OSTI ID: 7032908
• Journal Information: J. Phys. Chem.; (United States), Vol. 90:25
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
PHASE TRANSFORMATIONS
TEMPERATURE DEPENDENCE
PHOSPHORUS OXIDES
VISCOSITY
ARRHENIUS EQUATION
EXPERIMENTAL DATA
GLASS
PHASE DIAGRAMS
THERMODYNAMIC PROPERTIES
CHALCOGENIDES
DATA
DIAGRAMS
EQUATIONS
INFORMATION
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PHOSPHORUS COMPOUNDS
PHYSICAL PROPERTIES
400201* - Chemical & Physicochemical Properties