Thermodynamic Analysis of the Crystallization Resistance of the Ge-S-Bi Glasses

Glass-forming systems based on GeSx have a wide practical application. Therefore, their crystallization from supercooled melt was studied in many works, mainly by differential scanning calorimetry and X-ray powder diffraction analysis. Explanation of the experimentally determined crystallization behavior using the thermodynamic method of Gibbs energy minimization enabled one to develop a predictive procedure for identifying the crystallizing phases and the temperature conditions of their separation, depending on the initial composition of the GeSxBi0.02 glass (x = 1.25, 1.35, 1.4, and 1.6), and also allowed one to formulate a thermodynamic factor of crystallization resistance of glass. Comparison of the Gibbs energy calculated using the associated solution model with the Gibbs energy values obtained experimentally in the supercooled solution region made it possible to find the standard enthalpy of formation for each glass composition. Finally, the supersaturation to crystallization, which is the basis of the thermodynamic factor of crystallization and is an index of the crystallization resistance of glass, is determined by the difference of the chemical potentials of a component of the glass-forming system in the crystalline state and in the supercooling solution state. The procedure to predict and choose crystallization-resistant glasses promotes technological developments of novel fiber optic light guides.