Thermodynamic assessment of the Ge-Si-O-Cl-H system

An assessed thermodynamic dataset for the Ge-Si-O-Cl-H system useful for application in the glass fiber industry is presented. The focus of the work is on the germanium-bearing species. Taking into account the available vapor pressure measurements on the Ge-O, Ge-Cl, Ge-Cl-H, and Ge-O-Cl systems, modifications have been made to the recommended data for the important oxide and halide species. The GeO₂-SiO₂ and GeCl₄-SiCl₄ binary systems have been thermodynamically optimized using simple models. The current dataset, when combined with the data from the FactSage™ database for the other required species/phases, can be used to make useful calculations of glass vapor equilibria pertinent to the manufacture of germanium-doped silica glass fibers using vapor deposition methods.