Correlation between Vogel Fulcher Tamman & Avramov Equation for Glass Viscosity

Abstract

Among many equations the VFT and Avramov equations can fit the glass viscosity data ranging from 101 to 1015 poise. The VFT equation needs 3 empirical constants (fitting parameter) to fit the viscosity data over a wide range. Whereas, Avramov equation is based on entropy – temperature correlation. When fitting a particular viscosity data over a wide range of viscosity it has been observed that both equation fall over each other with minimum deviation. So it would be logical to find out some correlation from that characteristic. In the present work an attempt has been made to find the origin of VFT constants by help of Avramov equation. Viscosity data of SiO2 based glass system has been taken in to account to find some correlations.