Fragility correlates thermodynamic and kinetic properties of glass forming liquids

• Published in: Materials research bulletin 2015-03, Vol.63, p.231-238
• Main Authors: Reddy, C.Narayana, Viswanatha, R., Chethana, B.K., Gowda, V.C.Veeranna, Rao, K.J.
• Format: Article
• Language: English
• Subjects: A. Amorphous materials; A. Glasses; BORATES; C. Differential scanning calorimetry; CALORIMETRY; COMPARATIVE EVALUATIONS; D. Specific heat; D. Thermodynamic properties; ENTROPY; GLASS; LIQUIDS; LITHIUM; MATERIALS SCIENCE; SPECIFIC HEAT; VISCOSITY
• ISSN: 0025-5408; 1873-4227
• DOI: 10.1016/j.materresbull.2014.12.014

The suggested new fragility parameter correlates viscosity and configurational entropy. [Display omitted] •A new fragility function, F=ΔT/ΔCp×Cpl/Tg has been proposed.•A three parameter viscosity function using the new F reproduces Angell fragility plot.•A new ΔCp function is derived which directly relates Adam–Gibbs function with the fragility based viscosity function. In our earlier communication we proposed a simple fragility determining function, ([NBO]/Vm3Tg), which we have now used to analyze several glass systems using available thermal data. A comparison with similar fragility determining function, ΔCp/Cpl, introduced by Chryssikos et al. in their investigation of lithium borate glasses has also been performed and found to be more convenient quantity for discussing fragilities. We now propose a new function which uses both ΔCp and ΔT and which gives a numerical fragility parameter, F whose value lies between 0 and 1 for glass forming liquids. F can be calculated through the use of measured thermal parameters ΔCp, Cpl, Tg and Tm. Use of the new fragility values in reduced viscosity equation reproduces the whole range of viscosity curves of the Angell plot. The reduced viscosity equation can be directly compared with the Adam–Gibbs viscosity equation and a heat capacity function can be formulated which reproduces satisfactorily the ΔCp versus ln(Tr) curves and hence the configurational entropy.